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  • Phytochrome
  • Springer  (200)
  • National Academy of Sciences
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  • 1
    Electronic Resource
    Electronic Resource
    Blue light regulation of the growth of Prunus persica plants in a long term experiment: morphological and histological observations (1999)
    Springer
    Trees 14 (1999), S. 169-176 
    Details
    ISSN: 0931-1890
    Keywords: Key words Prunus persica ; Photomorphogenesis ; Phytochrome ; Cryptochrome ; Blue light
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Prunus persica plants were grown under prolonged exposure to different light treatments to determine the interaction between the blue light (BL) receptor and phytochrome and/or an independent BL response in the photoregulation of shoot and leaf development. Different light conditions were established in growth chambers by changing both the state of phytochrome and the BL photon flux density (PFD) at constant photosynthetically active radiation (PAR). Furthermore, to evaluate the independent action of the BL photoreceptor, increasing amounts of BL photons were added to the light emitted by low-pressure sodium (LPS) lamps without altering irradiance and phytochrome photoequilibrium. Applying the principle of equivalent light action, the observed blue inhibition of shoot elongation, leaf expansion and thickness were clearly related to a specific BL receptor because the state of phytochrome for each treatment was nearly identical. Increasing amounts of blue photons to light emitted from LPS lamps decreased shoot elongation, whereas leaf expansion was negatively affected only at the highest blue level, suggesting a specific fluence dependence response to BL for each organ and tissue. The BL effect was evident in reducing the thickness of all the leaf tissues except for the upper epidermis, which became thicker. This could be the result of an adaptation to protect the underlying photosynthetic apparatus. Other morphological and anatomical responses to the action of the BL receptor were greatly altered when the state of phytochrome changed in the plant tissues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00009760
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  • 2
    Electronic Resource
    Electronic Resource
    Phytochrome elicits the cryptic red-light signal which results in amplification of anthocyanin biosynthesis in sorghum (1999)
    Springer
    Planta 208 (1999), S. 80-87 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Action spectrum ; Anthocyanin ; Cryptic red-light signal ; Phytochrome ; High-irradiance response ; Sorghum (phytochrome)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Anthocyanin synthesis in Sorghum bicolor Moench induced by a low-fluence response of phytochrome (phy) is multiplicatively amplified by a cryptic red-light signal (CRS) produced by red light (R). The photoreceptor for CRS and its features in CRS production were studied. (i) An action spectrum determined with a 200-s light pulse of wavelengths from 347 to 693 nm had peaks at 657 and 378 nm. (ii) The CRS-producing effect of R, even as short a pulse as 20 s, was neither suppressed by an immediately subsequent far-red light (FR) pulse nor increased by placing a dark interval of 180 s between R and FR; simultaneous FR, however, suppressed the R action in accordance with the resulting ratios of the FR-absorbing form (Pfr) to total phy. (iii) The effect of R increased with increasing fluence rate to plateau at the same fluence rate regardless of the pulse length, but the level of this plateau depended on the pulse length. (iv) The effect of R increased with increasing pulse length when compared at the same fluence, whether saturating or unsaturating; thus, no reciprocity law holds. These results indicate that the photoreceptor for CRS production is a phy, Pfr being active, which presumably shows very fast dark reversion to the R-absorbing form without absorbing FR. The possible CRS-production mechanism of the phy and its significance in the so-called R high-irradiance response of phy are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050537
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  • 3
    Electronic Resource
    Electronic Resource
    Ion antagonism in phytochrome-mediated calcium-dependent germination of turions of Spirodela polyrhiza (L.) Schleiden (1999)
    Springer
    Planta 208 (1999), S. 583-587 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Calcium ; Germination ; Phytochrome ; Signal transduction ; Spirodela (germination) ; Turion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The light-dependent germination response of turions (resting fronds) is mediated by phytochrome and requires the presence of Ca2+ in the medium (K.-J. Appenroth and H. Augsten, 1990, Photochem. Photobiol. 52: 61–65). The Ca2+ requirement of germination is apparent only in the presence of exogenous Mg2+. A competitive ion antagonism was demonstrated between Ca2+ and Mg2+ in this physiological response; Mg2+ could also be replaced by Ba2+ or Sr2+. Without exog-enous Mg2+, a Ca2+ concentration as low as 0.9 μM fulfilled the Ca2+ requirement. This type of ion antagonism resembled the competitive Ca/Mg interaction reported previously for calcium-binding proteins. The physiological response was blocked by inhibitors of Ca2+ uptake (verapamil, La3+). It was concluded that uptake of Ca2+ from the external medium is an essential step in the phytochrome-mediated germination of turions. The results are in agreement with the assumption that the uptake of Ca2+ is blocked at the side of entry by other alkaline earth ions. Treatment of turions with Mg2+ (1 mM) for 24 h at varying times after the red light pulse in otherwise virtually Ca2+-free KNO3 solution resulted in a response similar to a Ca2+ step-down treatment. This is in agreement with the assumption that the Ca2+- and the Mg2+-sensitive periods coincide. The ion interaction described here represents the first photophysiological example in plants of an antagonistic effect between Ca2+ and Mg2+ similar to that which occurs in vitro with calmodulin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050596
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  • 4
    Electronic Resource
    Electronic Resource
    Irradiance-dependent regulation of gravitropism by red light in protonemata of the moss Ceratodon purpureus (1999)
    Springer
    Planta 209 (1999), S. 299-307 
    Details
    ISSN: 1432-2048
    Keywords: Key words:Ceratodon (protonema ; tropism) ; Micro-gravity ; Phototropism ; Phytochrome ; Polarity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Apical cells of protonemata of the moss Ceratodon purpureus (Hedw.) Brid. are negatively gravitropic in the dark and positively phototropic in red light. Various fluence rates of unilateral red light were tested to determine whether both tropisms operate simultaneously. At irradiances ≥140 nmol m−2 s−1 no gravitropism could be detected and phototropism predominated, despite the presence of amyloplast sedimentation. Gravitropism occurred at irradiances lower than 140 nmol m−2 s−1 with most cells oriented above the horizontal but not upright. At these low fluence rates, phototropism was indistinct at 1 g but apparent in microgravity, indicating that gravitropism and phototropism compete at 1 g. The frequency of protonemata that were negatively phototropic varied with the fluence rate and the duration of illumination, as well as with the position of the apical cell before illumination. These data show that the fluence rate of red light regulates whether gravitropism is allowed or completely repressed, and that it influences the polarity of phototropism and the extent to which apical cells are aligned in the light path.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050636
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  • 5
    Electronic Resource
    Electronic Resource
    Phytochrome-controlled phototropism of protonemata of the moss Ceratodon purpureus: physiology of the wild type and class 2 ptr–mutants (1999)
    Springer
    Planta 209 (1999), S. 290-298 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Cell division ; Ceratodon ; Phototropism ; Phytochrome ; Polarotropism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Phototropism and polarotropism in protonemata of the moss Ceratodon purpureus are controlled by the photoreceptor phytochrome. One class of phototropism mutants is characterised by growing randomly when kept for a prolonged time (5 d or longer) in unilateral red light. It was found that a subclass of these mutants grows faster than the wild type, the rate of cell division and the length of the cells being increased. This difference is found for light-grown and dark-grown filaments. It is therefore suggested that the mutant phenotype neither results from a defect in phytochrome photoconversion nor from a defect in phytochrome-gradient formation. Instead, it is possible that a factor which is involved in both signal transduction of phototropism and regulation of cell size and cell division is deregulated. If dark-grown mutant filaments are phototropically stimulated for 24 h, they show a weak phototropic response. Phototropism and polarotropism fluence-rate effect curves for mutants were flattened and shifted to higher fluence rates compared with those for the wild type. With wild-type filaments, a previously unreported response was observed. At a low fluence rate, half of the filaments grew positively phototropically, while the other half grew negatively phototropically. It seems that under these conditions, a phytochrome gradient with two maxima for the far-red-absorbing form of phytochrome (Pfr) within the cross-section of the cell is displayed by the response of the filaments. At higher fluence rates, all filaments of the wild type grew towards the light. These data and results from microbeam irradiation experiments and from phototropism studies with filaments growing within agar, indicate that light refraction plays an important role in the formation of the Pfr gradient in phototropism of Ceratodon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050635
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  • 6
    Electronic Resource
    Electronic Resource
    Control of hypocotyl elongation in Arabidopsis thaliana by photoreceptor interaction (1999)
    Springer
    Planta 208 (1999), S. 257-263 
    Details
    ISSN: 1432-2048
    Keywords: Key words:Arabidopsis ; Cryptochrome ; Hypocotyl growth ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. In order to test the interaction of different phytochromes and blue-light receptors, etiolated seedlings of wild-type Arabidopsis thaliana (L.) Heynh., a phytochrome (phy) B-overexpressor line (ABO), and the photoreceptor mutants phyA-201, phyB-5, hy4-2.23n, fha-1, phyA-201/phyB-5, and phyA-201/hy4-2.23n were exposed to red and far-red light pulses after various preirradiations. The responsiveness to the inductive red pulses is primarily mediated by phyB which is rather stable in its far-red-absorbing form as demonstrated by a very slow loss of reversibility. Without preirradiation the red pulses had an impact on hypocotyl elongation only in PHYA mutants but not in the wild type. This indicates a suppression of phyB function by the presence of phyA. Preirradiation with either far-red or blue light resulted in an inhibition of hypocotyl elongation by red pulses in the wild type. Responsiveness amplification by far-red light is mediated by phyA and disappears slowly in the dark. The extent of responsiveness amplification by blue light was identical in the wild type and in the absence of phyA, or the cryptochromes cryl (hy4-2.23n) or cry2 (fha-1). Therefore, we conclude that stimulation of phyB by blue light preirradiation is either mediated by an additional still-unidentified blue-light-absorbing pigment or that phyA, cry1 and cry2 substitute for each other completely. Both blue and red preirradiation established responsiveness to red pulses in phyA-201/phyB-5 double mutants. These results demonstrate that inhibition of hypocotyl elongation by red pulses is not only mediated by phyB but also by a phytochrome(s) other than phyA and phyB.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050557
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  • 7
    Electronic Resource
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    Phytochrome-dependent modulation and re-induction of growth of the first rhizoid in Dryopteris paleacea Sw (1999)
    Springer
    Planta 208 (1999), S. 98-106 
    Details
    ISSN: 1432-2048
    Keywords: Key words:Dryopteris ; Gametophyte ; Intercellular signaling ; Phytochrome ; Rhizoid ; Tip growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Phytochrome-dependent growth in Dryopteris paleacea Sw. was investigated in young, developing gametophytes with respect to formation and differentiation of rhizoids. Under continuous red light (Rc), the first rhizoids grew synchronously by tip elongation at a constant rate of 240 μm · d−1 until formation and outgrowth of the second rhizoid. Cessation of growth of the first rhizoids and outgrowth of the second rhizoids showed a correlation in time assumed to be mediated by intercellular signaling. The first rhizoids showed two modes of response to actinic irradiations: (i) modulation of rhizoid growth, and (ii) re-induction of growth in non-growing rhizoids. In the former, the promotory effect of actinic irradiations on rhizoids pre-cultured under Rc determined both the time for which rhizoids continued to grow after transfer into darkness and the final rhizoid length. In the latter, re-induced growth was studied using non-growing rhizoids which were obtained after irradiation with a far-red light (FR) pulse at the end of the pre-culture in Rc and transfer into darkness for 3 d to stop growth. Re-induction of growth occurred with a lag phase of 36 to 48 h after formation of the FR-absorbing form of phytochrome (Pfr) by a red light (R) pulse. From the incomplete R/FR reversibility it is evident that, here, coupling of Pfr to signal transduction is possible within minutes. Re-induction of growth possesses the advantage that the effect of actinic irradiations can be studied as an all-or-none response at the level of single gametophytes in future experiments. The present results clearly indicate that the developmental stage of the whole gametophyte, i.e. temporal and spatial patterns undergone during development, affects the regulation of rhizoid growth by the external factor light.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050539
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  • 8
    Electronic Resource
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    Cytoskeletal changes during resumption of tip growth in nongrowing protonemal cells of the fernAdiantum capillus-veneris L. (1999)
    Springer
    Protoplasma 207 (1999), S. 195-202 
    Details
    ISSN: 1615-6102
    Keywords: Adiantum capillus-veneris ; Microfilament ; Microtubule ; Nuclear migration ; Phytochrome ; Tip growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Nongrowing, two-celled protonemata of the fernAdiantum capillus-veneris L. resume tip growth within the apical cell upon irradiation with red light. In this study, the phenomenon of growth resumption was analyzed with reference to changes in cytoskeletal organization. Continuous observations of apical cells with time lapse video-microscopy revealed that the nucleus migrated toward the tip ca. 1.9 h after the onset of red light, much earlier than the initiation of tip growth, which took place ca. 8.5 h after irradiation. Cytoskeletal organization was observed at various time points during growth resumption by fluorescent staining of microfilaments (MFs) and microtubules (MTs) with rhodamine-phalloidin and anti-tubulin antibodies. At 2 h after red-light irradiation, endoplasmic MF and MT strands appeared at the apical end of nucleus. These strands extended into the apical endoplasm, where filaments were rare prior to irradiation. Many fine filaments branched from the strands to the cell periphery, including the cortex of the apical-dome region. At this time, cortical circular arrays of MTs and MFs, normally found in the growing apex of protonemal cells, were absent. Both MT and MF circular arrays appeared during the resumption of tip growth concomitantly. The half-maximum appearance of MT and MF circular arrays within a population occurred at 5.4 h and 5.8 h after red-light irradiation, respectively. Thus, the process of red-light-induced resumption of tip growth in fern protonemal cell is composed of a series of events. These events include: (1) the appearance of strands extending from the nucleus toward the apical cortex and the migration of nucleus toward the apex; (2) the formation of circular MT and MF arrays at the sub-apical cortex; and (3) the initiation of cell growth at the apex. These results reflect the significant roles of MF and MT cytoskeleton in the resumption of tip growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01283000
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  • 9
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    Characterization of the gene encoding the apoprotein of phytochrome B2 in tomato, and identification of molecular lesions in two mutant alleles (1999)
    Springer
    Molecular genetics and genomics 261 (1999), S. 901-907 
    Details
    ISSN: 1617-4623
    Keywords: Key words Photomorphogenic mutants ; Phytochrome ; Tomato ; PHYB2 ; Intron splicing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The structure of the gene encoding the apoprotein of tomato phytochrome B2 (PHYB2) has been determined from genomic and cDNA sequences. The coding region is organized into four exons, like almost every other angiosperm phytochrome (phy). The deduced phyB2 apoprotein (PHYB2) consists of 1121 amino acids, with 82, 74 and 70% identity to tomato PHYB1, Arabidopsis PHYB, and Arabidopsis PHYD, respectively. In order to facilitate the identification of new mutants, we constructed a double mutant that is deficient in phyA and phyB1. When grown in white light, this mutant becomes only slightly taller than wild type and is similar in phenotype to the monogenic phyB1-deficient mutant. This double mutant has been used as the parent line for mutagenesis with γ radiation. Several recessive mutants with long hypocotyls and reduced anthocyanin content were selected under white light and screened for mutations in PHYB2, PHYE and PHYF. Two of the triple-mutant lines, designated 55H and 70F, had elongated hypocotyls and fruit trusses, and pale immature fruits. Both belong to the same complementation group and both were found to have defects in PHYB2. Line 70F was found by Northern analysis to have a slightly larger PHYB2 transcript. Part or all of the intron between the second and third exons was found to be retained following RT-PCR of PHYB2 mRNA from line 70F. Three base substitutions were detected near the donor splice site for this intron, including a change from the consensus /GT to /GA at the 5′ end of this intron. In every case, the C-terminal 164 amino acids of PHYB2 were replaced by 59 nonsense amino acids followed by a stop codon. Sequencing of PHYB2 from 55H revealed a single-nucleotide deletion near the end of the third exon, resulting in one incorrect codon followed immediately by a stop codon. The predicted mutant apoprotein in 55H is 90 residues shorter than wild-type PHYB2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004380051037
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  • 10
    Electronic Resource
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    Photoreceptors of higher plants (1998)
    Springer
    Planta 206 (1998), S. 479-492 
    Details
    ISSN: 1432-2048
    Keywords: Key words:Arabidopsis mutant ; Blue-light receptor ; Phytochrome ; Signal transduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050425
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  • 11
    Electronic Resource
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    A single red-light pulse leads to a block of greening in the high-pigment-1 mutant of tomato (1998)
    Springer
    Planta 206 (1998), S. 685-688 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Chlorophyll ; Greening ; hp-1 mutant ; Phytochrome ; Solanum (mutant)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. A single pulse of red light (R) given to 4-d-old etiolated high-pigment-1 (hp-1) mutant tomato (Solanum lycopersicum L.) seedlings followed by a 3-d dark period is demonstrated to result in a block of greening in subsequent white light. Wild-type seedlings green normally under this regime. The block of greening in the hp-1 mutant depends on the length of the dark period before and after the R pulse and operates via the low-fluence-response mode of phytochrome action. This block of greening takes place in hp-1 double mutants lacking either phytochrome A or phytochrome B1, but is absent in the hp-1 triple mutant lacking both phytochromes A and B1. These observations enable a screen to be devised for new phytochrome B1 mutants either within the photoreceptor or mutants defective in phytochrome B1-signalling steps which result in loss of capacity to green, by mutagenising the phytochrome A-deficient hp-1, fri double mutant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050448
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  • 12
    Electronic Resource
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    Ionic mechanism and role of phytochrome-mediated membrane depolarisation in caulonemal side branch initial formation in the mossPhyscomitrella patens (1997)
    Springer
    Planta 201 (1997), S. 109-118 
    Details
    ISSN: 1432-2048
    Keywords: Depolarisation ; Ion transport ; Signal transduction ; Physcomitrella ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In caulonemal filaments of the mossPhyscomitrella patens (Hedw.), red light triggers a phytochrome-mediated transient depolarisation of the plasma membrane and the formation of side branch initials. Three-electrode voltage clamp and ion flux measurements were employed to elucidate the ionic mechanism and physiological relevance of the red-light-induced changes in ion transport. Current-voltage analyses indicated that ion channels permeable to K+ and Ca2+ are activated at the peak of the depolarisation. Calcium influx evoked by red light coincided with the depolarisation in various conditions, suggesting the involvement of voltage-gated Ca2+ channels. Respective K+ fluxes showed a small initial influx followed by a dramatic transient efflux. A role of anion channels in the depolarising current is suggested by the finding that Cl− efflux was also increased after red light irradiation. In the presence of tetraethylammonium (10 mM) or niflumic acid (1 μM), which block the red-light-induced membrane depolarisation and ion fluxes, the red-light-promoted formation of side branch initials was also abolished. Lanthanum (100 μM), which inhibits K+ fluxes and part of the initial Ca2+ influx activated by red light, reduced the development of side branch initials in red light by 50%. The results suggest a causal link between the red-light-induced ion fluxes and the physiological response. The sequence of events underlying the red-light-triggered membrane potential transient and the role of ion transport in stimulus-response coupling are discussed in terms of a new model for ion-channel interaction at the plasma membrane during signalling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01007695
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  • 13
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    Response of actin microfilaments during phytochrome-controlled growth of maize seedlings (1997)
    Springer
    Protoplasma 200 (1997), S. 154-162 
    Details
    ISSN: 1615-6102
    Keywords: Actin ; Cell elongation ; Confocal microscopy ; Zea mays ; Microfilaments ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In seedlings of maize (Zea mays L. cv. Percival), growth is controlled by the plant photoreceptor phytochrome. Whereas coleoptile growth is promoted by continuous far-red light, a dramatic block of mesocotyl elongation is observed. The response of the coleoptile is based entirely upon light-induced stimulation of cell elongation, whereas the response of the mesocotyl involves light-induced inhibition of cell elongation. The light response of actin microfilaments was followed over time in the epidermis by staining with fluorescence-labelled phalloidin. In contrast to the underlying tissue, epidermal cells are characterized by dense longitudinal bundles of microfilaments. These bundles become loosened during phases of rapid elongation (between 2–3 days in irradiated coleoptiles, between 5–6 days in dark-grown coleoptiles). The condensed bundles re-form when growth gradually ceases. The response of actin to light is fast. If etiolated mesocotyls are transferred to far-red light, condensation of microfilaments can be clearly seen 1 h after the onset of stimulation together with an almost complete block of mesocotyl elongation. The observations are discussed in relation to a possible role of actin microfilaments in the signal-dependent control of cell elongation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01283291
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  • 14
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    Phytochrome- and blue-light-absorbing pigment-mediated directional movement of chloroplasts in dark-adapted prothallial cells of fernAdiantum as analyzed by microbeam irradiation (1996)
    Springer
    Planta 198 (1996), S. 488-493 
    Details
    ISSN: 1432-2048
    Keywords: Adiantum (prothallial cell) ; Blue-lightabsorbing pigment ; Chloroplast movement (directional) ; Microbeam irradiation ; Phytochrome ; Signal-transduction chain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When prothalli ofAdiantum capillus-veneris L. were kept for 2 d in the dark, chloroplasts gathered along the anticlinal walls (Kagawa and Wada, 1994, J Plant Res 107: 389–398). In these dark-adapted prothallial cells, irradiation with a microbeam (10 gm in diameter) of red (R) or blue light (B) for 60 s moved the chloroplasts towards the irradiated locus during a subsequent dark period. Chloroplasts located less than 20 gm from the center of the R microbeam (18 J·m−2) moved towards the irradiated locus. The higher the fluence of the light, the greater the distance from which chloroplasts could be attracted. The B microbeam was less effective than the R microbeam. Chloroplasts started to move anytime up to 20 min after the R stimulus, but with the B microbeam the effect of the stimulus was usually apparent within 10 min after irradiation. The velocity of chloroplast migration was independent of light-fluence in both R and B and was about - 0.3 μm·min−1 between 15 min and 30 min after irradiation. Whole-cell irradiation with far-red light immediately after R- and B-microbeam irradiations demonstrated that these responses were mediated by phytochrome and a blue-light-absorbing pigment, respectively. Sequential treatment with R and B microbeams, whose fluence rates were less than the threshold values when applied separately, resulted in an additive effect and induced chloroplast movement, strongly suggesting that signals from phytochrome and the blue-light-absorbing pigment could interact at some point before the induction of chloroplast movement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00620067
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  • 15
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    The light-induced reduction of the gravitropic growth-orientation of seedlings of Arabidopsis thaliana (L.) Heynh. is a photomorphogenic response mediated synergistically by the far-red-absorbing forms of phytochromes A and B (1996)
    Springer
    Planta 199 (1996), S. 511-514 
    Details
    ISSN: 1432-2048
    Keywords: Arabidopsis ; Gravitropism ; phyB-1 ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Hypocotyls of dark-grown seedlings of Ara bidosis thaliana exhibit a strong negative gravitropism, which is reduced by red and also by long-wavelength, far-red light treatments. Light treatments using phytochrome A (phyA)- and phytochrome B (phyB)-deficient mutants showed that this response is controlled by phyB in a red/far-red reversible way, and by phyA in a non-reversible, very-low-fluence response. Crosses of the previously analyzed phyB-1 allele (in the ecotype Landsberg erecta background) to the ecotype Nossen wild-type (WT) background resulted in a WT-like negative gravitropism in darkness, indicating that the previously described gravitropic randomization observed with phyB-1 in the dark is likely due to a second mutation independent of that in the PHYB gene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00195180
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  • 16
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    Regulation of the subunit composition of tomato plastidic glutamine synthetase by light and the nitrogen source (1996)
    Springer
    Planta 200 (1996), S. 213-220 
    Details
    ISSN: 1432-2048
    Keywords: Gene expression ; Glutamine synthetase ; Nitrogen source ; Phosphinothricin ; Phytochrome ; Solanum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The co-action of light and the N-source in the regulation of the expression of the single-copy gene encoding plastidic glutamine synthetase (GS-2) and of the multigene family encoding cytosolic glutamine synthetase (GS-1) was investigated in the cotyledons of tomato (Lycopersicon esculentum L.). Light, acting at red/far red or at blue regions of the spectrum increased the abundance of the GS-2 gene product and induced a modification of GS-2 subunits, resulting in the appearance of two GS-2 proteins exhibiting different molecular weights. The magnitude of the light stimulation of GS-2 gene expression was independent of the nitrogen source. However, following red- or far-red-light treatment of etiolated tomato cotyledons, two GS-2 proteins were found when nitrate was the N-source, while only one GS-2 protein was present with ammonium as the sole nitrogen source. Thus, light of specific wavelengths and N-substrates seem to act in concert to regulate GS-2 subunit composition. Tomato GS-1 gene expression was unaffected by light. Ammonium provided externally increased the level of the tomato GS-1 protein. Irrespective of the N-source or the light quality, the GS-1 subunits were represented by polypeptides of similar molecular weight in tomato cotyledons. However, phosphinothricin-induced inhibition of GS activity resulted in the appearance of at least one additional GS-1 polypeptide in etiolated or in green tomato cotyledons. In addition, impairment of GS activity in green tomato cotyledons by phosphinothricin was correlated with an increased level of the GS-1 transcript. Taken together, our data suggest a metabolic control of GS-1 gene expression in green tomato cotyledons.
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    URL: http://dx.doi.org/10.1007/BF00208311
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    Changes in gene expression in the leaf of Lolium temulentum L. Ceres during the photoperiodic induction of flowering (1996)
    Springer
    Planta 200 (1996), S. 32-40 
    Details
    ISSN: 1432-2048
    Keywords: Biological clock ; CAB genes ; Flowering(induction) ; Gene expression ; Lolium ; Photoperiodism ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Unifoliated plants of Lolium temulentum L. Ceres were induced to flower by a unique 24-h long day (LD) consisting of the extension of the regular 8-h short day (SD) (400 μmol photons·m−2·s−1, fluorescence + incandescence) with incandescence at 10–15 μmol photonsm −2·s−1. The polyadenylated-RNA complement of leaf blade tissues was analysed at 4-h intervals during the photoperiod extension in LD vs. SD, by using two-dimensional polyacrylamide gel electrophoresis to resolve in-vitro-translated products. Of the 991 spots that were analysed, none appeared or disappeared during the inductive cycle, i.e. no qualitative effect of floral induction was detected, at any time. Sixty-eight spots were found whose intensity was influenced by lengthening of the photoperiod; 50 of them, i.e. ca. 5% of the population analysed, were affected before the end of the extension period and were thus potentially related to floral induction. Many of these RNAs were not quantitatively constant during a 24-h cycle in SD. Seven of them oscillated according to the ‘light-on’ and the ‘light-off’ signals, among which three seemed to be controlled by phytochrome since their relative amount increased under the standard light conditions but decreased under incandescence even faster than in darkness. The large majority of other RNAs varied with a timing that was not clearly driven by the alternation of light and darkness, indicating that genes related to the biological clock may be especially sensitive to the lengthening of the photoperiod. Furthermore, seven spots were observed that underwent a phase-shift in LD, which consisted, for six of them, of a phase advance of 4–8 h. The steady-state level of CAB mRNA was analysed because the CAB gene family (encoding the chlorophyll a/b-binding proteins of the light-harvesting complexes) is known to be controlled both by the biological clock and phytochrome. In SD, the level was high in the light and low in darkness; the fluctuation was conducted by a circadian rhythm. When plants were exposed to the inductive LD, the peak of mRNA accumulation that was expected according to the endogenous rhythmicity was abolished, possibly because of the change in light quality during the LD extension.
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  • 18
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    Molecular analysis of tri-mutant alleles in tomato indicates the Tri locus is the gene encoding the apoprotein of phytochrome B1 (1996)
    Springer
    Planta 199 (1996), S. 152-157 
    Details
    ISSN: 1432-2048
    Keywords: Phytochrome ; Lycopersicon ; Photomorphogenic mutants ; Photomorphogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Four monogenic recessive tomato (Lycopersicon esculentum Mill.) mutants at the temporarily red light-Insensitive (tri) locus (tri 1, tri 2in the genetic background breeding line GT; tri 3, tri 4in the genetic background cultivar Moneymaker) were studied. These mutants had slightly longer hypocotyls under white light than the wild type (WT). Western-blot analysis showed that the tri 1mutant was deficient in a relatively lightstable phytochrome apoprotein (116 kDa) that was recognized in the WT by an antibody to tobacco phytochrome B; tri 2had a 166-kDa band reduced in abundance; and tri 2and tri 4had bands reduced in molecular mass, approx. 105 and 95 kDa, respectively. These patterns were also found in light-grown plants. Northern-blot analysis for PHYB1 mRNA showed for tri 2a transcript approx. 2 kb larger, for tri 4, a transcript of WT size, but much reduced in abundance and for tri 1and tri 3transcripts equivalent in size and abundance to WT. In these mutants the transcripts of other members of the tomato phytochrome gene family (PHYA, PHYB2, PHYE, PHYF) were indistinguishable in size and abundance from WT. Thus, it appears that the tri locus specifically affects PHYB1 gene expression. Unlike phytochrome-B mutants in other plants, de-etiolated seedlings of the tri mutants exhibited normal responses to end-of-day far-red (EODFR) light and supplementary far-red light during the day. Since the holophytochromes of types B1 and B2 (phyB1 and phyB2) are closely related, it is proposed that there might be redundancy between them for these responses.
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    URL: http://dx.doi.org/10.1007/BF00196891
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  • 19
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    Calcium-dependent membrane depolarisation activated by phytochrome in the moss Physcomitrella patens (1996)
    Springer
    Planta 199 (1996), S. 352-358 
    Details
    ISSN: 1432-2048
    Keywords: Membrane depolarisation ; Physcomitrella ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In caulonemal filaments of Physcomitrella patens which had been preincubated in the dark for 24 h, irradiation with red light (640 nm, fluence rate 85 μmol · m−2 · s−1) evoked (i) the development of side branch initials and (ii) a rapid, but transient, depolarisation of the plasma membrane by 90 ± 13 mV from a resting potential of -178 ± 13 mV. This was followed by a transient hyperpolarisation to a value 21± 8 mV more negative than the original membrane potential. The refractory period for the transient depolarisation was between 12 and 15 min. The fluence rate of red light required to evoke maximal depolarisation was about 80 μmol · m−2 · s−1 for a 1-min pulse. At this fluence rate, a depolarising response could be recorded for pulse lengths as small as 7 s. The transient depolarisation was insensitive to 3-(3′,4′dichlorophenyl)-1,1-dimethyl urea (DCMU) and was unchanged in plants bleached by growth on norflurazon (SAN 9789). Furthermore, the electrical response could be blocked by simultaneous application of far-red light. These results suggest the involvement of the photoreceptor phytochrome in the response. Removing Ca2+ from the external medium or replacing Ca2+ with Mg2+ blocked the depolarisation. The depolarisation could also be blocked by the K+ channel-blocker tetraethylammonium (10 mM) and the Cl− channel-blocker niflumic acid (1 μM). Conversely, although calcium channel-antagonists such as nifedipine and lanthanides, applied at a concentration of 100 μM, also altered the response, they did not block it. A possible ionic mechanism for the membrane potential transient is advanced, and the physiological significance discussed in the context of early events in the phytochrome signalling pathway.
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    URL: http://dx.doi.org/10.1007/BF00195726
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  • 20
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    Structural basis for the red light induced repolarization of tip growth in caulonema cells ofCeratodon purpureus (1996)
    Springer
    Protoplasma 192 (1996), S. 189-198 
    Details
    ISSN: 1615-6102
    Keywords: Calcium ; Microfilaments ; Microtubules ; Moss protonema ; Phototropism ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Two dynamic changes are associated with the phytochrome-regulated phototropic response in tip cells of the mossCeratodon purpureus: a tip-located gradient shift of chlortetracy-cline (CTC)-stained calcium and a structural reorganization of apical microfilaments (MFs). We examined the interdependence of these processes. Cells were treated with the antimicrotubule drug oryzalin, the antimicrofilament drug cytochalasin-D, and the calcium channel blocker nifedipine. respectively. The effects on phototropic growth, on the structural alignment of the cytoskeleton (microtubules, MTs; microfilaments) and on the distribution of CTC-stained calcium were studied under each of these conditions. In gravitropically growing tip cells the apical MFs form a cortical collar-like structure, consisting of actin bundles with a parallel axial alignment. These MFs point towards the presumptive growing point, a weakly stained region in the tip of the cell from which bundles are absent. MTs are present in the cortex and in the endoplasm of the tip, predominantly oriented longitudinally. The MTs converge within the central apex. The cells show a steep tip-to-base CTC-calcium gradient with its highest signal in the central apex. Destruction of MTs by 1 μM oryzalin induces several translocational effects: (i) the growing zone and phototropic outgrowth shift from the apex to subapical parts of the cell; (ii) the structural integrity of the apical MFs and the tip-to-base alignment of the CTC-calcium gradient are disturbed; and (iii) the red light induced gradient shift and the reorientation of MFs proceed in an expanded area spanning from the tip to subapical parts of the cell. Cytochalasin-D (10 μg/ml) destroys the MFs. Under these conditions tip growth stops and the phototropic outgrowth is suppressed. The apical MT-structure and the CTC-calcium gradient are not influenced by the agent. Unilateral red light still induces the light-directed translocation of the gradient. Tip cells “memorize” a unilateral irradiation applied during growth inhibition with cytochalasin-D. After recovery in darkness the cells start to grow in the former light direction. The restoration of the MFs precedes the outgrowth. The structural alignment of the rebuilt actin bundles indicates the future growth direction. The calcium channel blocker nifedipine (10 βM) also inhibits tip growth and concurrently phototropic outgrowth. Nifedipine destroys the CTC-calcium gradient and apical MFs; MTs are not influenced by the channel blocker.
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    URL: http://dx.doi.org/10.1007/BF01273891
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  • 21
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    Dynamic changes in the organization of microfilaments associated with the photocontrolled motility of chloroplasts in epidermal cells ofVattisneria (1996)
    Springer
    Protoplasma 195 (1996), S. 18-24 
    Details
    ISSN: 1615-6102
    Keywords: Chloroplasts ; Epidermal cell ; Microfilament ; Orientation movement ; Phytochrome ; Vallisneria gigantea Graebner
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Using time-lapse video microscopy, we performed a semiquantitative investigation of the movement of chloroplasts on the cytoplasmic layer that faces the outer periclinal wall (P side) of epidermal cells of leaves of the aquatic angiospermVallisneria gigantea Graebner. Under continuous irradiation with red light (650 nm, 0.41 W/m2), the movement of chloroplasts on the P side was transiently accelerated within 5 min. The increased movement began to decrease at around 20 min and fell below the original level after 40 to 60 min of irradiation with red light. The acceleration and deceleration of movement of chloroplasts on the P side seemed to lead directly to the increase and the subsequent decrease in the rate of migration of chloroplasts from the P side to the anticlinal layers of cytoplasm, which are responsible for the accumulation of chloroplasts on the P side, as we demonstrated previously. In the presence of inhibitors of photosynthesis, the accelerated movement of chloroplasts was maintained for as long as the chloroplasts were irradiated with red light. The rapid acceleration and deceleration of the movement of chloroplasts could be observed repeatedly with sequential irradiation with red and then far-red light (746 nm, 0.14 W/m2). Concomitantly with the loss of motility of chloroplasts on the P side, a dynamic change in the configuration of microfilaments, from a network to a honeycomb, occurred on the P side.
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    URL: http://dx.doi.org/10.1007/BF01279183
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    Phosphorylation/dephosphorylation steps are key events in the phytochrome-mediated enhancement of nitrate reductase mRNA levels and enzyme activity in maize (1996)
    Springer
    Molecular genetics and genomics 251 (1996), S. 599-608 
    Details
    ISSN: 1617-4623
    Keywords: Key words Nitrate reductase ; Phytochrome ; Phosphorylation ; Protein kinase C ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We provide evidence to show that the increase in nitrate reductase (NR) transcript level stimulated by red light is mediated via a phosphorylation-dependent step. The light-stimulated enhancement of NR transcript level was significantly inhibited by H-7, a protein kinase inhibitor, whereas okadaic acid (OKA), a phosphatase inhibitor, had no effect. Phorbol myristate acetate (PMA), an activator of protein kinase C (PKC) enhanced the NR transcript level in dark-grown leaves. No correlation between changes in NR transcript level and NR activity (NRA) was observed. Inhibition of NRA by OKA and stimulation by H-7 indicated that NRA is increased by dephosphorylating the enzyme. We have identified a protein kinase (C type) that can phosphorylate the purified NR in vitro without the involvement of other accessory proteins. By in vivo labelling with 32P and immunoprecipitation of NR with NR antibodies it was found that in the presence of OKA most NR protein (NRP) was present in phosphorylated state, while with H-7 the reverse was seen. The red (R) and far-red (FR) light reversible experiments suggested that phytochrome (Pfr, an active form) stimulation of NRA is mediated by dephosphorylation of the enzyme, suggesting that Pfr regulates both NR transcription and NRA via phosphorylation/dephosphorylation steps controlled by separate signal transduction pathways.
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    URL: http://dx.doi.org/10.1007/BF02173650
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    Phosphorylation/dephosphorylation steps are key events in the phytochrome-mediated enhancement of nitrate reductase mRNA levels and enzyme activity in maize (1996)
    Springer
    Molecular genetics and genomics 251 (1996), S. 599-608 
    Details
    ISSN: 1617-4623
    Keywords: Nitrate reductase ; Phytochrome ; Phosphorylation ; Protein kinase C ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We provide evidence to show that the increase in nitrate reductase (NR) transcript level stimulated by red light is mediated via a phosphorylation-dependent step. The light-stimulated enhancement of NR transcript level was significantly inhibited by H-7, a protein kinase inhibitor, whereas okadaic acid (OKA), a phosphatase inhibitor, had no effect. Phorbol myristate acetate (PMA), an activator of protein kinase C (PKC) enhanced the NR transcript level in darkgrown leaves. No correlation between changes in NR transcript level and NR activity (NRA) was observed. Inhibition of NRA by OKA and stimulation by H-7 indicated that NRA is increased by dephosphorylating the enzyme. We have identified a protein kinase (C type) that can phosphorylate the purified NR in vitro without the involvement of other accessory proteins. By in vivo labelling with32P and immunoprecipitation of NR with NR antibodies it was found that in the presence of OKA most NR protein (NRP) was present in phosphorylated state, while with H-7 the reverse was seen. The red (R) and far-red (FR) light reversible experiments suggested that phytochrome (Pfr, an active form) stimulation of NRA is mediated by dephosphorylation of the enzyme, suggesting that Pfr regulates both NR transcription and NRA via phosphorylation/dephosphorylation steps controlled by separate signal transduction pathways.
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    URL: http://dx.doi.org/10.1007/BF02173650
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    Photoregulation systems for light-oriented chloroplast movement (1996)
    Springer
    Journal of plant research 109 (1996), S. 139-146 
    Details
    ISSN: 1618-0860
    Keywords: Blue-light photoreceptor ; Chloroplast movement ; Dichroic orientation (photoreceptors) ; Multiple photosystems ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Movements of the chloroplasts induced by a directional stimulus of light are found to occur in various plant materials ranging from algae to terrestrial angiosperms. Depending on the fluence rate of light, chloroplasts move toward the area of the maximum light absorption and escape from it, which are named as low- and high-fluence-rate responses, respectively. In most materials the effective wavelengths are exclusively found in the blue-UV region of spectrum, (a) flavin pigment(s) being considered as the photoreceptor, while in a few species of plants phytochrome is involved. The arrangement of chloroplasts as a result of the movement depends on the orientation of the electrical vector of light, which reflects the dichroic orientation of the photoreceptor for perception of light direction. Photosystems involved in these responses, however, are not only for perception of light direction, but also for realization of the movement and for holding of the chloroplasts in the reached site. Possible interactions and dual roles of photosystems in regulation of chloroplast movement are discussed.
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    URL: http://dx.doi.org/10.1007/BF02344539
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    The roles of inorganic nitrogen salts in maintaining phytochrome- and gibberellin A3-mediated germination control in skotodormant lettuce seeds (1996)
    Springer
    Journal of plant growth regulation 15 (1996), S. 159-165 
    Details
    ISSN: 1435-8107
    Keywords: Germination ; Gibberellin ; Imbibition ; Lettuce ; Nitrogen ; Phytochrome ; Skotodormant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Skotodormant seeds of Lactuca sativa Grand Rapids imbibed in darkness for 10 days (10-day DS) germinated poorly upon terminal treatment with red light (R) or gibberellin A3 (GA3). Inorganic nitrogen salts in the imbibition solutions reduced seed skotodormancy. Ten-day DS seeds, imbibed in 25 mm salt solutions followed by terminal R, germinated 99% if imbibed in NH4NO3, 70% if imbibed in KNO3 or NH4Cl, and 55% if imbibed in NaNO3. Seeds imbibed in higher salt concentrations germinated fully upon terminal R treatment. Seeds imbibed in 25 mm NH4Cl or in 50 mm NH4NO3 germinated completely upon GA3 treatment. Osmotic effects of imbibition media accounted for only part of the effect, since seeds imbibed in 50 mm CaCl2 or NaCl germinated poorly following R or GA3 treatment. Seeds imbibed in 500 mm polyethylene glycol (PEG) 1000 or mannitol solutions for 10 days still exhibited skotodormancy. Treatments of R or GA3 did not stimulate germination in seeds imbibed in mannitol, but germination was complete if seeds were given 1-h acid immersion plus a water rinse before the terminal R or GA3 treatment. Seeds imbibed in 50–500 mm PEG during 10-day DS germinated significantly better in response to terminal R. Terminal GA3 significantly improved germination only in seeds imbibed at 500 mm PEG. Pfr appeared to function in mannitol-imbibed seed only after an acid treatment. Seed exposure to inorganic nitrogen salts during the 10-day DS maintained seed sensitivity to terminal R or GA3 treatment. The depth of seed skotodormancy was related to the availability of inorganic nitrogen and also involved the levels of Pfr or endogenous GA3.
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    URL: http://dx.doi.org/10.1007/BF00190579
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    Polarized light induces nuclear migration in prothallial cells of Adiantum capillus-veneris L. (1995)
    Springer
    Planta 196 (1995), S. 775-780 
    Details
    ISSN: 1432-2048
    Keywords: Adiantum ; Blue-light-absorbing pigment ; Nuclear photo-orientation ; Phytochrome ; Polarized light ; Prothallus (fern)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In irradiated prothallial cells of Adiantum capillus-veneris L. the nuclei are located at the periclinal wall, whereas they are located at the anticlinal wall in darkness (Kagawa and Wada, 1993, Protoplasma 177, 82–85). The migration of the nuclei could be induced in cells preadapted in the dark, by irradiation with both polarized red (R) and blue light (B). When the dark-adapted prothallial cells were irradiated from the horizontal direction with horizontally vibrating polarized light, the nuclei moved from the anticlinal walls to the periclinal walls. It took 3 h for 50% of the nuclei to leave the anticlinal walls. Vertically vibrating polarized light did not have such an effect, and the nuclei stayed at the anticlinal walls. Simultaneous irradiation of polarized R or B with non-polarized far-red light reduced the effect of R but not of B, indicating the involvment of phytochrome and a blue light-absorbing pigment in the R and B effects, respectively. When light-adapted prothallial cells were irradiated from the horizontal direction with vertically vibrating polarized light, the nuclei migrated from the periclinal walls to the anticlinal walls. About half of the nuclei left the periclinal walls within 6 h after the onset of the vertically polarized light. When the prothalli were irradiated with horizontally vibrating polarized light, it took more than 18 h. These results suggest that the light-induced nuclear migration is caused by a gradient of light-activated photoreceptors, i.e. phytochrome and blue-light-absorbing pigment.
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    URL: http://dx.doi.org/10.1007/BF00197344
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    Polarized light induces nuclear migration in prothallial cells ofAdiantum capillus-veneris L. (1995)
    Springer
    Planta 196 (1995), S. 775-780 
    Details
    ISSN: 1432-2048
    Keywords: Adiantum ; Blue-light-absorbing pigment ; Nuclear photo-orientation ; Phytochrome ; Polarized light ; Prothallus (fern)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In irradiated prothallial cells ofAdiantum capillus-veneris L. the nuclei are located at the periclinal wall, whereas they are located at the anticlinal wall in darkness (Kagawa and Wada, 1993, Protoplasma177, 82–85). The migration of the nuclei could be induced in cells preadapted in the dark, by irradiation with both polarized red (R) and blue light (B). When the dark-adapted prothallial cells were irradiated from the horizontal direction with horizontally vibrating polarized light, the nuclei moved from the anticlinal walls to the periclinal walls. It took 3 h for 50% of the nuclei to leave the anticlinal walls. Vertically vibrating polarized light did not have such an effect, and the nuclei stayed at the anticlinal walls. Simultaneous irradiation of polarized R or B with non-polarized far-red light reduced the effect of R but not of B, indicating the involvment of phytochrome and a blue light-absorbing pigment in the R and B effects, respectively. When light-adapted prothallial cells were irradiated from the horizontal direction with vertically vibrating polarized light, the nuclei migrated from the periclinal walls to the anticlinal walls. About half of the nuclei left the periclinal walls within 6 h after the onset of the vertically polarized light. When the prothalli were irradiated with horizontally vibrating polarized light, it took more than 18 h. These results suggest that the light-induced nuclear migration is caused by a gradient of light-activated photoreceptors, i.e. phytochrome and blue-light-absorbing pigment.
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    URL: http://dx.doi.org/10.1007/BF01106773
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    Coupling of phytochrome B to the control of hypocotyl growth in Arabidopsis (1995)
    Springer
    Planta 196 (1995), S. 23-29 
    Details
    ISSN: 1432-2048
    Keywords: Arabidopsis ; High-irradiance reaction ; Hypocotyl growth ; Photomorphogenic mutants ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Etiolated seedlings of the wild-type (WT) and of the phyB-1 mutant of Arabidopsis thaliana (L.) Heynh. were exposed to red-light (R) and far-red light (FR) treatments to characterize the action of phytochrome B on hypocotyl extension growth. A single R or FR pulse had no detectable effects on hypocotyl growth. After 24-h pre-treatment with continuous FR (FRc) a single R, compared to FR pulse inhibited (more than 70%) subsequent hypocotyl growth in the WT but not in the phyB-1 mutant. This effect of FRc was fluence-rate dependent and more efficient than continuous R (Rc) or hourly FR pulses of equal total fluence. Hypocotyl growth inhibition by Rc was larger in WT than phyB-1 seedlings when chlorophyll screening was reduced either by using broadband Rc (maximum emission 610 nm) or by using narrow-band Rc (658 nm) over short periods (24 h) or with seedlings bleached with Norflurazon. Hourly R or R + FR pulses had similar effects in WT and phyB-1 mutant etiolated seedlings. It is concluded that phytochrome B is not the only photoreceptor of Rc and that the action of phytochrome B is enhanced by a FRc high-irradiance reaction. Complementary experiments with the phyA-201 mutant indicate that this promotion of a phytochrome B-mediated response occurs via co-action with phytochrome A.
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    URL: http://dx.doi.org/10.1007/BF00193213
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    Regulation of the orientation movement of chloroplasts in epidermal cells of Vallisneria: cooperation of phytochrome with photosynthetic pigment under low-fluence-rate light (1995)
    Springer
    Planta 197 (1995), S. 257-263 
    Details
    ISSN: 1432-2048
    Keywords: Chloroplast ; Epidermal cell (of Vallisneria) ; Orientation movement (of chloroplasts) ; Photosynthesis ; Phytochrome ; Vallisneria (Chloroplast movement)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In epidermal cells of the leaves of the aquatic angiosperm Vallisneria gigantea Graebner, the chloroplasts accumulate in the outer periclinal layer of cytoplasm (P side) under light at low fluence rates. The nature of such intracellular orientation of chloroplasts was investigated in a semiquantitative manner. Time-lapse video microscopy revealed that, while irradiation with red light (650 nm, 0.41 W · m−2) rapidly accelerated the migration of chloroplasts, not only from the anticlinal layers of cytoplasm (A sides) to the P side but also from the P side to the A sides, the increased rate of migration in both directions returned to the control rate upon subsequent irradiation with far-red light (746nm, 0.14W · m−2). These effects of red and far-red light could be observed repeatedly, both in the presence and in the absence of inhibitors of photosynthesis, suggesting the involvement of phytochrome as the photoreceptor. After saturating irradiation with red light, the increased rate of migration of chloroplasts from the P side to the A sides declined more rapidly than the increased rate of migration in the opposite direction. This imbalance in the migration of chloroplasts between the two opposing directions resulted in the accumulation of chloroplasts on the P side. The more rapid decline in the rate of migration of chloroplasts from the P side to the A sides than in the opposite direction was not observed in the presence of an inhibitor of photosynthesis. It appears, therefore, that phytochrome and photosynthetic pigment cooperatively regulate the accumulation of chloroplasts on the P side through modulation of the nature of the movement of the chloroplasts.
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    URL: http://dx.doi.org/10.1007/BF00202645
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    Co-action between phytochrome B and HY4 in Arabidopsis thaliana (1995)
    Springer
    Planta 197 (1995), S. 213-218 
    Details
    ISSN: 1432-2048
    Keywords: Arabidopsis (hy4 mutant) ; Blue-light photo-receptors ; Hypocotyl growth ; Photomorphogenic mutants ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A combination of physiological and genetic approaches was used to investigate whether phytochromes and blue light (BL) photoreceptors act in a fully independent manner during photomorphogenesis of Arabidopsis thaliana (L.) Heynh. Wild-type seedlings and phyA, phyBand hy4 mutants were daily exposed to 3 h BL terminated with either a red light (R) or a far-red light (FR) pulse. In wild-type and phyA-mutant seedlings, BL followed by an R pulse inhibited hypocotyl growth and promoted cotyledon unfolding. The effects of BL were reduced if exposure to BL was followed by an FR pulse driving phytochrome to the R-absorbing form (Pr). In the wild type, the effects of R versus FR pulses were small in seedlings not exposed to BL. Thus, maximal responses depended on the presence of both BL and the FR-absorbing form of phytochrome (Pfr) in the subsequent dark period. Impaired responses to BL and to R versus FR pulses were observed in phyB and hy4 mutants. Simultaneous irradiation with orange light indicated that BL, perceived by specific BL photoreceptors (i.e. not by phytochromes), required phytochrome B to display a full effect. These results indicate interdependent co-action between phytochrome B and BL photoreceptors, particularly the HY4 gene product. No synergism between phytochrome A (activated by continuous or pulsed FR) and BL photoreceptors was observed.
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    URL: http://dx.doi.org/10.1007/BF00202639
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    Acclimation of Arabidopsis thaliana to the light environment: regulation of chloroplast composition (1995)
    Springer
    Planta 197 (1995), S. 475-481 
    Details
    ISSN: 1432-2048
    Keywords: Arabidopsis ; Blue light ; Photoreceptor ; Photosynthesis ; Photosystem stoichiometry ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The regulation by light of the composition of the photosynthetic apparatus was investigated in Arabidopsis thaliana (L.) Heynh. cv. Landsberg erecta. When grown in high- and low-irradiance white light, wild-type plants and photomorphogenic mutants showed large differences in their maximum photosynthetic rate and chlorophyll a/b ratios; such changes were abolished by growth in red light. Photosystem I (PSI) and PSII levels were measured in wild-type plants grown under a range of light environments; the results indicate that regulation of photosystem stoichiometry involves the specific detection of blue light. Supplementing red growth lights with low levels of blue light led to large increases in PSII content, while further increases in blue irradiance had the opposite effect; this latter response was abolished by the hy4 mutation, which affects certain events controlled by a blue-light receptor. Mutants defective in the phytochrome photoreceptors retained regulation of photosystem stoichiometry. We discuss the results in terms of two separate responses controlled by blue-light receptors: a blue-high-fluence response which controls photosystem stoichiometry; and a blue-low-fluence response necessary for activation of such control. Variation in the irradiance of the red growth light revealed that the blue-high-fluence response is attenuated by red light; this may be evidence that photosystem stoichiometry is controlled not only by photoreceptors, but also by photosynthetic metabolism.
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    URL: http://dx.doi.org/10.1007/BF00196669
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    Reorganization of microfilaments in protonemal tip cells of the mossCeratodon purpureus during the phototropic response (1995)
    Springer
    Protoplasma 188 (1995), S. 59-69 
    Details
    ISSN: 1615-6102
    Keywords: Actin ; Microfilaments ; Microtubules ; Moss protonema ; Phototropism ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The F-actin distribution in caulonemal tip cells of the mossCeratodon purpureus was examined by rhodamine-phalloidin staining. Gravitropically-growing caulonemal tip cells of the moss possess a distinct alignment of microfilaments (MFs) in their apices. Axially oriented actin bundles run from subapical regions to the apex where they converge towards a central area of the tip, although bundles are absent from the central area itself thus forming a collar-like structure. During a unilateral red light irradiation the actin strands of the apical dome become reoriented towards the irradiated apical flank and still surround an area free of MFs, the point of prospective outgrowth. This process is closely correlated with the morphological effect of bulging and precedes the light-directed outgrowth. The collar structure is essential for the tubular growth form. In darkness, under the influence of antimicrotubule agents the structure is decomposed, the actin strands drift along the cell flanks and finally accumulate in randomly distributed areas where further growth takes place. The microtubules (MTs) are not involved in the phytochromemediated reorientation of the microfilaments. Unilateral red light suppresses the distorting effect of antimicrotubule drugs and restores the collar structure with a pronounced light-directed orientation. Instead, the MTs seem to be responsible for restricting the reorientation to the cell tip. This notion is based on the observation that the small area in the apical dome, which is normally the exclusive location of the light-regulated MF rearrangement, extends towards the cell base when MT inhibitors are applied before the unilateral red light irradiation. This in turn leads to a non-tubular expansion of the light-directed cell flank.
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    URL: http://dx.doi.org/10.1007/BF01276796
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    Effect of light and gibberellic acid on chromosome endoreduplication in leaf epidermis ofTriticum durum Desf. (1995)
    Springer
    Protoplasma 186 (1995), S. 57-62 
    Details
    ISSN: 1615-6102
    Keywords: Blue-light-absorbing photoreceptor ; Chromosome endo-reduplication ; Gibberellic acid ; Light ; Phytochrome ; Triticum durum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The first foliage leaf ofTriticum durum Desf., cvs. Capelli and Creso, was studied for the action of light and gibberellic acid on different aspects of plant growth. Creso is a short-strawed cultivar carrying theRht 1 gene, that influences both plant height and sensitivity to applied gibberellins. In this study, a cytophotometric analysis of chromosome endoreduplication in bulliform cells of the leaf epidermis was undertaken. The bulliform cells are arranged in long rows and comprise 4C, 8C, and 16C cells. The relative percentage of these cells was recorded under different light regimes and in the presence or absence of gibberellic acid (GA3). Our data indicate that light strongly affects the occurrence of chromosome endoreduplication. Although cvs. Cappelli and Creso show the same frequency of endo-reduplicated cells in the dark, all light treatments induce lower endo-polyploidy in cv. Creso whereas, in cv. Cappelli, a reduction in endo-polyploidy is observed when plants are irradiated with blue-lacking lights. This indicates that the action of a blue-light responsive photo-receptor determines high endopolyploidy. With respect to GA3 treatment, cv. Creso is again shown to be insensitive to hormone application, whereas in cv. Cappelli, gibberellic acid influences endopolyploidy level in the dark, causing very high frequencies of 8C cells and relatively high frequencies of 16C cells.
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    URL: http://dx.doi.org/10.1007/BF01276936
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    Avena phytochrome a overexpressed in transgenic tobacco seedlings differentially affects red/far-red reversible and very-low-fluence responses (cotyledon unfolding) during de-etiolation (1994)
    Springer
    Planta 192 (1994), S. 306-309 
    Details
    ISSN: 1432-2048
    Keywords: Cotyledon unfolding ; Low-fluence response ; Nicotiana (cotyledon, phytochrome) ; Phytochrome ; Transgenic plant ; Very-low-fluence response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Etiolated seedlings of tobacco (Nicotiana tabacum L.) were exposed to single light pulses predicted to establish different proportions of phytochrome in its far-red absorbing form (Pfr/P). The angle between the cotyledons was compared in wild-type and transgenic seedling overexpressing Avena phytochrome A over the range of both very low-fluence responses (VLFR) and low-fluence responses (LFR). The unfolding of the cotyledons increased linearly for 24 h after the light pulse. At this time the Pfr/P-response curve showed two linear segments. The segment below a calculated Pfr/P = 3% (i.e. VLFR) was steeper than the segment above 3% (i.e. LFR). In the VLFR range the slope was almost threefold higher in transgenic than wild-type seedlings. However, in the LFR range the difference was less than 50%. From these data we propose that Avena phytochrome A makes a higher contribution to VLFR than LFR in etiolated tobacco seedlings.
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    URL: http://dx.doi.org/10.1007/BF00198564
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    Phytochrome inhibits the effectiveness of gibberellins to induce cell elongation in rice (1994)
    Springer
    Planta 194 (1994), S. 256-263 
    Details
    ISSN: 1432-2048
    Keywords: Cell elongation ; Gibberellin sensitivity ; Microtubule ; Oryza ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Red light controls cell elongation in seedlings of rice (Oryza sativa L.) in a far-red-reversible manner (Nick and Furuya, 1993, Plant Growth Regul.12, 195–206). The role of gibberellins and microtubules in the transduction of this response was investigated in the rice cultivars Nihon Masari (japonica type) and Kasarath (indica type). The dose dependence of mesocotyl elongation on applied gibberellic acid (GA3) was shifted by red light, and this shift was reversed by far-red light. In contrast, coleoptile elongation was found to be independent of exogenous GA3. Nevertheless, it was inhibited by red light, and this inhibition was reversed by far-red light. The content of the active gibberellin species GA1 and GA4 was estimated by radio-immunoassay. In the mesocotyl, the gibberellin content per cell was found to increase after irradiation with red light, and this increase was far-red reversible. Conversely, the cellular gibberellin content injaponica-type coleoptiles did not exhibit any significant light response. Microtubules reoriented from transverse to longitudinal arrays in response to red light and this reorientation could be reversed by subsequent far-red light in both the coleoptile and the mesocotyl. This movement was accompanied by changes in cell-wall birefringence, indicating parallel reorientations of cellulose deposition. The data indicate that phytochrome regulates the sensitivity of the tissue towards gibberellins, that gibberellin synthesis is controlled in a negative-feedback loop dependent on gibberellin effectiveness, and that at least two hormone-triggered signal chains are linked to the cytoskeleton in rice.
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    URL: http://dx.doi.org/10.1007/BF01101686
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    Deletion analysis of a nitrite-reductase promoter from spinach in transgenic tobacco (1994)
    Springer
    Planta 194 (1994), S. 186-192 
    Details
    ISSN: 1432-2048
    Keywords: Gene expression ; Nitrate ; Nitrite-reductase ; Phytochrome ; Transgenic tobacco ; Nicotiana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Deletion analysis of the nitrite-reductase (NiR) promoter from spinach (Spinacia oleracea L.) fused to theβ-glucuronidase (GUS) reporter gene and introduced into tobacco (Nicotiana tabacum L., cv. Coker 176) indicates that basic elements required for light- and nitrate-dependent expression of the reporter are located within the promoter sequence -200/+131 relative to the transcription-initiation site. Detailed analysis indicates that positive regulatory elements exist between -200 and-330 as well as between -1450 and -1730, stimulating the level of GUS gene expression under all experimental conditions. Induction/reversion light-pulse experiments show that the promoter sequence -200/+131 suffices for phytochrome-mediated expression of the reporter gene. The observation that the NiR promoter from spinach exhibits full reversibility in transgenic tobacco confirms the previous conclusion that the NiR promoter from spinach fused to a GUS reporter gene and introduced into tobacco responds to nitrate and phytochrome as would be expected for tobacco (host) and not as would be expected for spinach (donor). When the plastids were damaged by photooxidation in the presence of Norflurazon, GUS activity levels were reduced to the same extent for all NiR-promoter/GUS fusions tested, indicating that the promoter region involved in the action of the ‘plastidic factor’ is between -200 and +131. The GUS gene expression under the control of the CaMV-35S promoter is not affected by light, nitrate or the ‘plastidic factor’.
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    URL: http://dx.doi.org/10.1007/BF01101677
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    Deletion analysis of a nitrite-reductase promoter from spinach in transgenic tobacco (1994)
    Springer
    Planta 194 (1994), S. 186-192 
    Details
    ISSN: 1432-2048
    Keywords: Gene expression ; Nitrate ; Nitrite-reductase ; Phytochrome ; Transgenic tobacco ; Nicotiana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Deletion analysis of the nitrite-reductase (NiR) promoter from spinach (Spinacia oleracea L.) fused to the β-glucuronidase (GUS) reporter gene and introduced into tobacco (Nicotiana tabacum L., cv. Coker 176) indicates that basic elements required for light- and nitrate-dependent expression of the reporter are located within the promoter sequence -200/+131 relative to the transcription-initiation site. Detailed analysis indicates that positive regulatory elements exist between -200 and-330 as well as between -1450 and -1730, stimulating the level of GUS gene expression under all experimental conditions. Induction/reversion light-pulse experiments show that the promoter sequence -200/+131 suffices for phytochrome-mediated expression of the reporter gene. The observation that the NiR promoter from spinach exhibits full reversibility in transgenic tobacco confirms the previous conclusion that the NiR promoter from spinach fused to a GUS reporter gene and introduced into tobacco responds to nitrate and phytochrome as would be expected for tobacco (host) and not as would be expected for spinach (donor). When the plastids were damaged by photooxidation in the presence of Norflurazon, GUS activity levels were reduced to the same extent for all NiR-promoter/GUS fusions tested, indicating that the promoter region involved in the action of the ‘plastidic factor’ is between -200 and +131. The GUS gene expression under the control of the CaMV-35S promoter is not affected by light, nitrate or the ‘plastidic factor’.
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    Phytochrome inhibits the effectiveness of gibberellins to induce cell elongation in rice (1994)
    Springer
    Planta 194 (1994), S. 256-263 
    Details
    ISSN: 1432-2048
    Keywords: Cell elongation ; Gibberellin sensitivity ; Microtubule ; Oryza ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Red light controls cell elongation in seedlings of rice (Oryza sativa L.) in a far-red-reversible manner (Nick and Furuya, 1993, Plant Growth Regul. 12, 195–206). The role of gibberellins and microtubules in the transduction of this response was investigated in the rice cultivars Nihon Masari (japonica type) and Kasarath (indica type). The dose dependence of mesocotyl elongation on applied gibberellic acid (GA3) was shifted by red light, and this shift was reversed by far-red light. In contrast, coleoptile elongation was found to be independent of exogenous GA3. Nevertheless, it was inhibited by red light, and this inhibition was reversed by far-red light. The content of the active gibberellin species GA1 and GA4 was estimated by radio-immunoassay. In the mesocotyl, the gibberellin content per cell was found to increase after irradiation with red light, and this increase was far-red reversible. Conversely, the cellular gibberellin content in japonica-type coleoptiles did not exhibit any significant light response. Microtubules reoriented from transverse to longitudinal arrays in response to red light and this reorientation could be reversed by subsequent far-red light in both the coleoptile and the mesocotyl. This movement was accompanied by changes in cell-wall birefringence, indicating parallel reorientations of cellulose deposition. The data indicate that phytochrome regulates the sensitivity of the tissue towards gibberellins, that gibberellin synthesis is controlled in a negative-feedback loop dependent on gibberellin effectiveness, and that at least two hormone-triggered signal chains are linked to the cytoskeleton in rice.
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    URL: http://dx.doi.org/10.1007/BF00196396
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    Density-dependent regulation of ramet recruitment by the red:far-red ratio of solar radiation: a field evaluation with the bunchgrass Schizachyrium scoparium (1994)
    Springer
    Oecologia 97 (1994), S. 462-469 
    Details
    ISSN: 1432-1939
    Keywords: Population regulation ; Schizachyrium scoparium ; Ramet recruitment ; Phytochrome ; Red:far-red ratio
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Depressions in the red to far-red ratio (R:FR) of solar radiation arising from the selective absorption of R (600–700 nm) and scattering of FR (700–800 nm) by chlorophyll within plant canopies may function as an environmental signal directly regulating axillary bud growth and subsequent ramet recruitment in clonal plants. We tested this hypothesis in the field within a single cohort of parental ramets in established clones of the perennial bunchgrass, Schizachyrium scoparium. The R:FR was modified near leaf sheaths and axillary buds at the bases of individual ramets throughout the photoperiod without increasing photosynthetic photon flux density (PPFD) by either (1) supplementing R beneath canopies to raise the naturally low R:FR or (2) supplementing FR beneath partially defoliated canopies to suppress the natural R:FR increase following defoliation. Treatment responses were assessed by simultaneously monitoring ramet recruitment, PPFD and the R:FR beneath individual clone canopies at biweekly intervals over a 12-week period. Neither supplemental R nor FR influenced the rate or magnitude of ramet recruitment despite the occurrence of ramet recruitment in all experimental clones. In contrast, defoliation with or without supplemental FR beneath clone canopies reduced ramet recruitment 88% by the end of the experiment. The hypothesis stating that the R:FR signal directly regulates ramet recruitment is further weakened by evidence demonstrating that (1) the low R:FR-induced suppression of ramet recruitment is only one component of several architectural modifications exhibited by ramets in response to the R:FR signal (2) immature leaf blades, rather than leaf sheaths or buds, function as sites of R:FR perception on individual ramets, and (3) increases in the R:FR at clone bases following partial canopy removal are relatively transient and do not override the associated constraints on ramet recruitment resulting from defoliation. A depressed R:FR is probably of greater ecological significance as a signal of competition for light in vegetation canopies than as a density-dependent signal which directly regulates bud growth and ramet recruitment.
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    Phytochrome-mediated phototropism inAdiantum cuneatum young leaves (1994)
    Springer
    Journal of plant research 107 (1994), S. 181-186 
    Details
    ISSN: 1618-0860
    Keywords: Adiantum ; Blue-light-absorbing pigment ; Fern ; Leaf ; Phototropism ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phototropism of youngAdiantum fern leaves is induced by red light as well as blue light. The red light response is mediated by phytochrome. This is the first evidence of phytochrome action in diploid fern tissue. The blue light response is mainly mediated not by phytochrome, but probably by a blue light-absorbing pigment as in the case of almost all plants and fungi. The red light-induced phototropism becomes detectable within 2 hr after the onset of unilateral light. The highest bending rate is about 10 degrees/hr, which occurs between 3–5 hr after the induction of the tropic response. The bending region is about 6–8 mm from the highest point of the coiled crozier where the growth rate becomes slow.
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    URL: http://dx.doi.org/10.1007/BF02346015
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    Brief irradiation with red or blue light induces orientational movement of chloroplasts in dark-adapted prothallial cells of the fernAdiantum (1994)
    Springer
    Journal of plant research 107 (1994), S. 389-398 
    Details
    ISSN: 1618-0860
    Keywords: Adiantum capillus-veneris (prothallus) ; Blue light-absorbing pigment ; Chloroplast orientational movement ; Microbeam ; Phytochrome ; Polarized light
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Orientational movement of chloroplasts was induced by a brief irradiation with red light (R) or blue light (B) in dark-adapted prothallial cells ofAdiantum, whose chloroplasts had gathered along the cell dividing wall (i.e., the anticlinal wall). When the whole dark-adapted prothallia were irradiated from a horizontal direction (i.e., from their lobes) with horizontally vibrating polarized R (H pol. R) for 10 or 3 min, the chloroplast left the anticlinal walls and spread over the prothallial surface (i.e., the periclinal walls) within 1–2 hr after the onset of irradiation, returning to the anticlinal wall (dark-position) within 10 hr. However, vertically vibrating polarized R (V pol. R) for 10 min did not induce the movement towards periclinal walls. The R effect was cancelled by non-polarized far-red light (FR) irradiation just after the R irradiation. Irradiation with H pol. B for 10 or 3 min but not with V pol. B could also induce a similar movement of chloroplasts, although the chloroplasts returned within 4 hr. The effect of H pol. B, however, was not cancelled by the subsequent FR irradiation. When a part of the dark-adapted cell at the prothallial surface was irradiated from above with a microbeam of R or B for 1 min, chloroplasts of the cell in the dark-position moved towards the irradiated locus in subsequent darkness. However, in the neighboring cells, orientational movement was not induced by either R or B microbeams. These results show that in dark-adapted prothallial cells, both brief irradiation with R and B can induce chloroplast photo-orientation and that the photoreceptors are phytochrome and blue light-absorbing pigment, respectively. It is also clear that effects of both R and B irradiation do not transfer to neighboring cells.
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    Response of a nitrite-reductase 3.1-kilobase upstream regulatory sequence from spinach to nitrate and light in transgenic tobacco (1993)
    Springer
    Planta 189 (1993), S. 440-442 
    Details
    ISSN: 1432-2048
    Keywords: Gene expression ; Nitrate ; Nitrite reductase ; Phytochrome ; Transgenic tobacco ; Nicotiana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the present study the question was addressed of whether the nitrite-reductase (NIR-)promoter from spinach (Spinacia oleracea L.), fused to a reporter gene (bacterial β-glucuronidase, GUS) and introduced into tobacco (Nicotiana tabacum L.) responds to nitrate and light in accordance with spinach (donor) or in accordance with tobacco (host). The data obtained at the GUS enzyme level as well as at the transcript level allow an unambiguous answer to this question: GUS gene expression under the control of the NIR-promoter from spinach responds to nitrate and light in accordance with the host (tobacco). Expression of the promoter-less GUS gene was not induced by any treatment.
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    Temporal and light regulation of the expression of three phytochromes in germinating seeds and young seedlings of Avena sativa L. (1993)
    Springer
    Planta 189 (1993), S. 384-390 
    Details
    ISSN: 1432-2048
    Keywords: Avena ; Gene expression (protein level) ; Photoregulation (phytochrome) ; Phytochrome ; Temporal regulation (phytochrome)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An oat (Avena sativa L.) plant contains at least three phytochromes, which have monomeric masses of 125, 124, and 123 kilodaltons (kDa) (Wang et al., 1991, Planta 184, 96–104). The 124-kDa phytochrome is most abundant in dark-grown seedlings, while the other two phytochromes predominate in light-grown seedlings. Using three monoclonal antibodies, each specific to one of the three phytochromes, we have monitored by immunoblot assay the expression of these three phytochromes in the 5 d following onset of imbibition of seeds. On a per-organism basis, each of these three phytochromes increased in abundance for the first 3 d in the light, or for the first 4 d in darkness, after which they each began to decrease in quantity. When 3-d-old dark-grown seedlings were transferred to the light, the abundance of each of these three phytochromes decreased both in absolute amount and relative to the phytochrome levels in control seedlings kept in darkness. In contrast, when 3-d-old light-grown seedlings were transferred to darkness, the abundance of the 124-kDa and 125-kDa phytochromes increased while that of 123-kDa phytochrome remained unchanged. In each case, the level of phytochrome was greater than that of control seedlings maintained in the light. Thus, in addition to temporal regulation, all three phytochromes exhibit photoregulated expression at the protein level, although the magnitude of this photoregulation varies substantially.
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    Photomorphogenic mutants of Arabidopsis thaliana reveal activities of multiple photosensory systems during light-stimulated apical-hook opening (1993)
    Springer
    Planta 191 (1993), S. 214-221 
    Details
    ISSN: 1432-2048
    Keywords: Apical hook opening ; Arabidopsis (mutants) ; Blue light photoreceptor ; De-etiolation ; Photomorphogenesis ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Fluence rate-response curves were generated for red-, far-red-, and blue-light-stimulated apical-hook opening in seedlings of several photomorphogenic mutants of Arabidopsis thaliana (L.) Heynh. Compared to wild-type plants, hook opening was reduced in the phytochrome-deficient hy1, hy2, and hy6 mutants in red and far-red light at all fluence rates tested, and in low-fluence blue light, but was normal under high-irradiance blue light. In contrast, the blue-light-response mutants (blu1, blu2, and blu3) lacked the high-irradiance-dependent hook-opening response in blue light while hook opening was normal in low-fluence blue light and in red and farred light at all fluence rates tested. Hook opening in the phytochrome-B-deficient hy3 mutant was similar to wild type in all light conditions tested. The effects of the different mutations on light-induced hook opening indicate that a phytochrome(s) other than phytochrome B mediates hook opening stimulated by red, far-red and lowfluence blue light, while a blue-light-absorbing photoreceptor mediates the blue-light-sensitive high-irradiance response. Although the phytochrome and blue-light photosensory systems appear to work independently for the most part, some of their signal-transduction components may interact since the hy4, and hy5 mutants showed reduced hook-opening responses under conditions dependent on the phytochrome and blue-light-photosensory systems.
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    Enhancement of red-light-induced anthocyanin synthesis in sorghum first internodes by moderate low temperature given in the pre-irradiation culture period (1993)
    Springer
    Planta 191 (1993), S. 238-245 
    Details
    ISSN: 1432-2048
    Keywords: Anthocyanin synthesis ; Low temperature ; Phytochrome ; Red light ; Sorghum (anthocyanin, phytochrome) ; Ultraviolet light-B
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Anthocyanin synthesis in the broom sorghum, Sorghum bicolor Moench cvs. Acme Broomcorn and Sekishokuzairai-Fukuyama, is mediated separately or synergistically by an ultraviolet light-B (UV-B) photoreceptor and phytochrome. When seedlings were exposed to moderate low temperatures ranging from 12 to 20° C before irradiation, only the phytochrome-mediated anthocyanin synthesis was markedly enhanced compared with the control, which was kept throughout at 24° C; synthesis mediated by the UV-B photoreceptor was unaffected. The effectiveness of an exposure to 20° C increased as the duration of exposure increased up to 24 h and as the time of exposure became closer to the time of irradiation. However, when seedlings were exposed to 20° C from after irradiation until harvest, anthocyanin syntheses induced by both UV-B and red light were equally suppressed, probably due to the general reduction of metabolism involved in anthocyanin synthesis that is a consequence of lower temperature. The results support the view that the signal transduction of the pyhtochrome system is different from that of the UV-B photoreceptor, and indicate that the phytochrome system may involve a step or steps which are amplified by a previous exposure to the moderate low temperature.
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    Half-lives of oat mRNAs in vivo and in a polysome-based in-vitro system (1993)
    Springer
    Planta 189 (1993), S. 249-256 
    Details
    ISSN: 1432-2048
    Keywords: Actin ; Avena ; Chlorophyll-a/b-binding protein ; mRNA half-life ; Phytochrome ; β-Tubulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have used a cell-free polysome-based in-vitro mRNA-degradation system to investigate the halflives of plant cell mRNAs. In order to establish the fidelity of the in-vitro system, we used cordycepin to determine the in-vivo half-lives of β-tubulin and actin mRNAs in the primary leaves of 4-d-old etiolated oat (Avena sativa L.) seedlings. The in-vitro rank order of half-lives for phytochrome A (45 min), β-tubulin (105 min), and actin (220 min) mRNAs mimicked the in-vivo rank order. A pulse of red light given to excised etiolated primary leaves caused an in-vivo reduction in the half-life of β-tubulin mRNA. The selectivity of the polysome-based system was further demonstrated by the decrease in the half-life of β-tubulin mRNA (from 105 min to 60 min) induced by a pulse of red light given to the etiolated oat seedlings prior to isolation of polysomes. Red light did not affect the apparent half-lives of phytochrome A or actin mRNAs.
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    Action spectrum for light-induced formation of adventitious shoots in hairy roots of horseradish (1993)
    Springer
    Planta 189 (1993), S. 590-592 
    Details
    ISSN: 1432-2048
    Keywords: Action spectrum ; Adventitious bud formation ; Armoracia ; Hairy roots ; Light and bud formation ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An action spectrum was determined for lightinduced formation of adventitious shoots in hairy roots of horseradish (Armoracia rusticana Gaert., Mey. et Scherb.) cultured in vitro. Near ultraviolet (350–400 nm), blue (440–460 nm) and red light (600–680 nm) were most effective in inducing formation of adventitious buds. Farred light (730 nm) inhibited the promotive effect of all three wavelength regions. These results are consistent with induction by phytochrome(s) of adventitious shoots in hairy roots of horseradish.
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    URL: http://dx.doi.org/10.1007/BF00198224
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    Photocontrol of nitrite reductase gene expression in the barley seedling (Hordeum vulgare L.) (1993)
    Springer
    Planta 192 (1993), S. 110-117 
    Details
    ISSN: 1432-2048
    Keywords: Gene expression ; Nitrate ; Nitrite reductase (Control) ; Phytochrome ; Hordeum (nitrite reductase gene expression)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrite reductase (NIR, EC 1.7.7.1) — a key enzyme of nitrate assimilation — is known to be induced by nitrate and light. In the present work with barley (Hordeum vulgare L.) seedlings, control of NIR gene expression by light and its dependency on intact plastids was studied. The major results were as follows: (i) It was confirmed that a single isoform of NIR occurs in shoot and root. (ii) Any light-mediated increase of NIR activity is strictly correlated with an increase in cross-reacting material. (iii) Exogenous nitrate is absolutely required for NIR synthesis and the appearance of NIR transcripts. The nitrate effect is saturated at 10 mM. (iv) Light-pulse experiments and long-term light treatments indicate the involvement of phytochrome in the light response. (v) While a small light effect possibly occurs in the root, a strong action of phytochrome was observed in the shoot. (vi) Photooxidative treatments of plastids led to a strong decrease of the NIR level and almost abolished the appearance of NIR transcripts. (vii) With plastids intact, application of nitrate (10 mM) caused the appearance of a considerable transcript level even in darkness. Light treatments in the presence of nitrate stimulated the transcript level further. (viii) Since a correlation between transcript level and rate of NIR increase was found it was concluded that in barley — in contrast to mustard, spinach and tobacco — NIR gene expression is controlled predominantly, if not exclusively, at the level of transcript accumulation.
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    URL: http://dx.doi.org/10.1007/BF00198700
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    Reorientation of microtubules at the outer epidermal wall of maize coleoptiles by phytochrome, blue-light photoreceptor, and auxin (1993)
    Springer
    Protoplasma 173 (1993), S. 103-112 
    Details
    ISSN: 1615-6102
    Keywords: Auxin ; Blue-light photoreceptor ; Microtubule orientation ; Phytochrome ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effects of red and blue light on the orientation of cortical microtubules (MTs) underneath the outer epidermal wall of maize (Zea mays L.) coleoptiles were investigated with immunofluorescent techniques. The epidermal cells of dark-grown coleoptiles demonstrated an irregular pattern of regions of parallel MTs with a random distribution of orientations. This pattern could be changed into a uniformly transverse MT alignment with respect to the long cell axis by 1 h of irradiation with red light. This response was transient as the MTs spontaneously shifted into a longitudinal orientation after 1–2 h of continued irradiation. Induction/reversion experiments with short red and far-red light pulses demonstrated the involvement of phytochrome in this response. In contrast to red light, irradiation with blue light induced a stable longitudinal MT alignment which was established within 10 min. The blue-light response could not be affected by subsequent irradiations with red or far-red light indicating the involvement of a separate blue-light photoreceptor which antagonizes the effect of phytochrome. In mixed light treatments with red and blue light, the blue-light photoreceptor always dominated over phytochrome which exhibited an apparently less stable influence on MT orientation. Long-term irradiations with red or blue light up to 6 h did not reveal any rhythmic changes of MT orientation that could be related to the rhythmicity of helicoidal cell-wall structure. Subapical segments isolated from dark-grown coleoptiles maintained a longitudinal MT arrangement even in red light indicating that the responsiveness to phytochrome was lost upon isolation. Conversely auxin induced a transverse MT arrangement in isolated segments even in blue light, indicating that the responsiveness to blue-light photoreceptor was eliminated by the hormone. These complex interactions are discussed in the context of current hypotheses on the functional significance of MT reorientations for cell development.
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    URL: http://dx.doi.org/10.1007/BF01378999
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    Photoreactivation of the UV light effects on growth of Scots pine (Pinus sylvestris L.) seedlings (1992)
    Springer
    Trees 6 (1992), S. 232-235 
    Details
    ISSN: 1432-2285
    Keywords: Pinus sylvestris L. ; UV-stress ; Phytochrome ; Photoreactivation ; Growth regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Ultraviolet-B light (UV-B) and ultraviolet-A light (UV-A) at higher doses exert a strong inhibitory (‘toxic’) effect on axis growth in Scots pine (Pinus sylvestris L.) seedlings. This effect is unrelated to control of growth rate by phytochrome. Rather, after a ‘toxic’ UV dose growth of the pine seedling no longer responded to phytochrome. Both, the effect of UV-B as well as the inhibiting effect of UV-A could be photoreactivated by blue light (B). The action of UV-A was 2 fold: (i) it exerted a ‘toxic’ effect which could be photoreactivated by B, and (ii) applied after UV-B it photoreactivated to some extent the ‘toxic’ UV-B effect. Obviously, the UV-A range causes a ‘toxic’ effect, and at the same time is capable of photoreactivating the ‘toxic’ UV effect. At higher doses the ‘toxic’ effect prevails.
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    URL: http://dx.doi.org/10.1007/BF00224341
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    Coaction of light, nitrate and a plastidic factor in controlling nitrite-reductase gene expression in tobacco (1992)
    Springer
    Planta 187 (1992), S. 381-387 
    Details
    ISSN: 1432-2048
    Keywords: Gene expression ; Nitrate ; Nitrate reductase (control) ; Phytochrome ; Nicotiana (nitrite reductase gene expression)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrite reductase (NIR; EC 1.7.7.1) — a key enzyme of nitrate reduction — is known to be induced by nitrate and light. In the present study with tobacco (Nicotiana tabacum L.) seedlings the dependency of NIR gene expression on nitrate, light and a plastidic factor was investigated to establish the nature of the coaction between these controlling factors. A cDNA clone coding for tobacco plastidic NIR was available as a probe. The major results were as follows: (i) The light effect on the appearance of NIR occurred predominantly through phytochrome. However, a specific blue-light effect was also involved. (ii) There was no effect of light on NIR appearance in the absence of nitrate while light exerted a strong effect when nitrate was provided. (iii) Anion-exchange chromatography revealed only a single form of NIR. While experiments involving plastid photooxidation indicated that this NIR is plastidic, a small residual level could not be eliminated by photooxidation. (iv) Northern blot analysis of NIR-transcript levels indicated that a low transcript level existed in the absence of nitrate and light; however, this level appeared to be increased slightly by light (in the absence of nitrate) and by nitrate (in the absence of light). A high transcript level was detected only when light as well as nitrate were provided. A low level was found when the plastids were damaged by photooxidation. It is concluded that plastidic NIR gene expression in tobacco requires positive control by a plastidic factor. Moreover, a synergistic action of phytochrome and nitrate is required to bring about a high transcript level. As found previously with mustard and spinach seedlings, there is no quantitative relationship between the transcript level and the rate of enzyme synthesis.
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    URL: http://dx.doi.org/10.1007/BF00195662
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    Light-regulated expression of the nitrate-reductase and nitrite-reductase genes in tomato and in the phytochrome-deficient aurea mutant of tomato (1992)
    Springer
    Planta 188 (1992), S. 39-47 
    Details
    ISSN: 1432-2048
    Keywords: Gene expression ; Lycopersicon ; Mutant (tomato, aurea) ; Nitrate reductase ; Nitrite reductase ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The phytochrome-deficient aurea mutant of tomato (Lycopersicon esculentum (L.) Mill) was used to investigate if phytochrome plays a role in the regulation of nitrate-reductase (NR, EC 1.6.6.1) and nitrite-reductase (NiR, EC 1.7.7.1) gene expression. We show that the expression of the tomato NR and NiR genes is stimulated by light and that this light response is mediated by the photoreceptor phytochrome. The red-light response of the NR and NiR genes was reduced in etiolated aurea seedlings when compared to isogenic wild-type cotyledons. The relative levels of NR mRNA and NiR transcripts and their diurnal fluctuations were identical in mature white-light-grown leaves of the wild-type and of the aurea mutant. The transcript levels for cab and RbcS (genes for the chlorophyll-a/b-binding protein of PSII and the small subunit of the enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase, respectively) in aurea leaves grown in white light were indistinguishable from the respective transcript levels in the leaves of the wildtype grown under the same conditions. Despite a severe reduction in the chlorophyll content, the rate of net CO2 uptake by leaves of the aurea mutant was only slightly reduced when compared to the rate of net photosynthesis of wild-type leaves. This difference in the photosynthetic performances of wild-type and aurea mutant plants disappeared during aging of the plants. The increase in zeaxanthin and the concomitant decrease in violaxanthin in leaves of the aurea mutant compared with the same pigment levels in leaves of the wild-type indicate that the activity of the xanthophyll cycle is increased in aurea leaves as a consequence of the reduced CO2-fixation capacity of the mutant leaves.
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    Light-regulated expression of the nitrate-reductase and nitrite-reductase genes in tomato and in the phytochrome-deficientaurea mutant of tomato (1992)
    Springer
    Planta 188 (1992), S. 39-47 
    Details
    ISSN: 1432-2048
    Keywords: Gene expression ; Lycopersicon ; Mutant (tomato,aurea) ; Nitrate reductase ; Nitrite reductase ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The phytochrome-deficientaurea mutant of tomato (Lycopersicon esculentum (L.) Mill) was used to investigate if phytochrome plays a role in the regulation of nitrate-reductase (NR, EC 1.6.6.1) and nitrite-reductase (NiR, EC 1.7.7.1) gene expression. We show that the expression of the tomato NR and NiR genes is stimulated by light and that this light response is mediated by the photoreceptor phytochrome. The red-light response of the NR and NiR genes was reduced in etiolatedaurea seedlings when compared to isogenic wild-type cotyledons. The relative levels of NR mRNA and NiR transcripts and their diurnal fluctuations were identical in mature white-light-grown leaves of the wild-type and of theaurea mutant. The transcript levels forcab andRbcS (genes for the chlorophyll-a/b-binding protein of PSII and the small subunit of the enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase, respectively) inaurea leaves grown in white light were indistinguishable from the respective transcript levels in the leaves of the wildtype grown under the same conditions. Despite a severe reduction in the chlorophyll content, the rate of net CO2 uptake by leaves of theaurea mutant was only slightly reduced when compared to the rate of net photosynthesis of wild-type leaves. This difference in the photosynthetic performances of wild-type andaurea mutant plants disappeared during aging of the plants. The increase in zeaxanthin and the concomitant decrease in violaxanthin in leaves of theaurea mutant compared with the same pigment levels in leaves of the wild-type indicate that the activity of the xanthophyll cycle is increased inaurea leaves as a consequence of the reduced CO2-fixation capacity of the mutant leaves.
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    Spectral-dependence of light-inhibited hypocotyl elongation in photomorphogenic mutants ofArabidopsis: evidence for a UV-A photosensor (1992)
    Springer
    Planta 188 (1992), S. 106-114 
    Details
    ISSN: 1432-2048
    Keywords: Arabidopsis ; Photomorphogenesis ; Blue/UV-A light ; Hypocotyl elongation ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photon fluence rate-response curves at different wavelengths were generated for the light-induced inhibition of hypocotyl elongation in seedlings of wildtype and photomorphogenic mutants ofArabidopsis thaliana. (L.) Heynh. Treatment of wild-type seedlings with continuous low-fluence-rate light (〈 1.0 μmol photons · m−2 · s−1) induced some inhibition of hypocotyl elongation at all wavelengths tested, with maximum inhibition in blue light. At higher fluence rates, inhibition reached a maximum of 70–80% in UV-A, blue, and far-red light. Fluence rate-response curves for seedlings ofblu1, a blue light-response mutant, showed a specific reduction in their response to blue light, but their response to UV-A, red, and far-red light was similar to that in wild-type seedlings. In contrast, the phytochromedeficient mutanthy6 showed a loss of response to lowfluence-rate light at all wavelengths, as well as to highfluence-rate far-red light. However,hy6 seedlings retained sensitivity to high-fluence-rate blue and UV-A light. The data support the conclusion that blue-lightand phytochrome-dependent photosensory systems regulate hypocotyl elongation independently and in an additive manner. Furthermore, hypocotyl inhibition in wild-type,blul, hy6 andblul-hy6 double mutants was indistinguishable in UV-A light, whereas marked differences were observed at other wavelengths, indicating the involvement of a third photosensory system with an absorption maximum in the UV-A.
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    Regulation of transcript level and synthesis of nitrate reductase by phytochrome and nitrate in turions of Spirodela polyrhiza (L.) Schleiden (1992)
    Springer
    Planta 188 (1992), S. 587-593 
    Details
    ISSN: 1432-2048
    Keywords: Gene expression ; Nitrate ; Nitrate reductase ; Phytochrome ; Spirodela ; Turion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Control by light and nitrate of the appearance of nitrate reductase (NR; EC 1.6.6.1) in the turions of Spirodela polyrhiza (L.) Schieiden was investigated during the pre-germination phase, i.e. up to 120 h after the transfer from after-ripening to germination conditions. Turions are particularily suited for this type of coaction study since control of nitrate uptake by light and long-distance transport of nitrate do not play a role. Control of NR gene expression was mainly studied between 72 and 120 h after transfer to germination conditions (phase II of the pre-germination process). It was found that the effect of light on NR appearance is exerted via phytochrome. The light effect on enzyme synthesis was only observed in the presence of nitrate. On the other hand, in darkness, the NR level decreased to almost zero even in the presence of an optimum supply of nitrate. It is concluded that in phase II a coaction of light (phytochrome) and nitrate is required to bring about NR synthesis. However, when nitrate was applied to turions — following a dark incubation without nitrate — the turions responded to nitrate even in darkness with strong NR synthesis. This response was augmented by light. The highest transcript levels were observed in the presence of both factors, light and nitrate. As a single factor, light was more effective in stimulating the transcript level than nitrate. However, no correlation between the transcript level and the rate of enzyme synthesis was observed. This is consistent with the previous conclusion (Schuster et al. 1988, Planta 174, 426–432) that in higher plants control at the transcript level is only coarse and does not determine quantitatively the output at the level of enzyme protein.
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    Effects of light quantity and quality during development on the morphology and stomatal physiology of Commelina communis (1992)
    Springer
    Oecologia 92 (1992), S. 188-195 
    Details
    ISSN: 1432-1939
    Keywords: Blue light ; Gas exchange ; Guard cell ; Phytochrome ; Red/far ; red ratio
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effects on plant growth and stomatal physiology of alterations in light quantity and quality during development were investigated in the C3 monocot, Commelina communis. Reduction in light intensity resulted in decreased branching and stem elongation, with effects more severe under “neutral shade” (R:FR≥1.0) than under “leaf shade” (R:FR≤0.4) conditions. Shade treatments had no effect on the leaf area or stomatal density of newly expanded leaves. Gas exchange measurements on leaves that had expanded under the different treatments indicated that a reduction in light intensity decreased the magnitude and slowed the kinetics of stomatal responses to pulses of blue light, particularly in plants from the neutral shade treatment. These results indicate that the specific stomatal response to blue light is plastic, and is modulated by the light environment prevailing during leaf development.
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    Surface-enhanced resonance Raman spectroscopy of phycocyanin and allophycocyanin (1992)
    Springer
    European biophysics journal 21 (1992), S. 193-198 
    Details
    ISSN: 1432-1017
    Keywords: Biliproteins ; Phycocyanin ; Allophycocyanin ; Phytochrome ; Surface-enhanced resonance Raman spectroscopy (SERRS)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract High quality surface-enhanced resonance Raman (SERR) spectra were recorded from native and denatured phycocyanin and allophycocyanin on ascorbic acid treated silver hydrosols. The visible-excited SERR and resonance Raman (RR) spectra of the phycobiliproteins were very similar, indicating a predominantly electromagnetic surface enhancement mechanism. Investigation of pH-induced denaturation ofx allophycocyanin has shown that even small differences in protein/chromophore conformational are sensitively reflected by the SERR spectra. Concerning the adsorption of the protein to the metal surface, the experiments have shown that: (i) there is limited possibility for changing protein conformation during the adsorption process, (ii) there are no changes after the protein has been adsorbed onto the silver surface and (iii) for each protein an optimal activation of the silver sol has to be found for recording proper SERR spectra. The results obtained on phycobiliproteins are also discussed in connection with the interpretation of phytochrome Raman spectra.
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    Structural domains of phytochrome deduced from homologies in amino acid sequences (1992)
    Springer
    The protein journal 11 (1992), S. 139-155 
    Details
    ISSN: 1573-4943
    Keywords: Phytochrome ; protein homology ; protein domains ; peptide conformation ; signal transduction ; photomorphogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A method of semiempirical identification of structural domains is proposed. The procedure is based on the comparison of amino acid sequences in groups of homologous proteins. This approach was tested using 32 known protein sequences from different cytochromeb 5, cytochromec, lysozyme, hemoglobin, and myoglobin proteins. The method presented was able to identify all structural domains of these reference proteins. A consensus secondary structure provided information on structural content of these domains predicting correctly 21 of 23 (91%) of α-helices. We applied this method to six homologous phytochrome sequences fromAvena, Arabadopsis, Cucurbita, Maize, Oryza, andPisum. Some of the identified domains can be assigned to the known tertiary structure categories. For example, an α/β domain is localized in the region known to stabilize the phytochrome chromophore in the red light absorbing form (Pr). One α-helical and one α/β domains are localized in regions important for the chromophore stabilization in the far-red absorbing form (Pfr). From an analysis of noncovalent interaction patterns in another domain it is proposed that a phytochrome dimer contact involves two segments localized between residues 730 and 821 (using numbering of aligned sequences). Also, a possible antiparallel β-sheet structure of this region has been suggested. According to this model, the long axis of the interacting structures is perpendicular to a twofold symmetry axis of the phytochrome dimer.
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    Control of the appearance of ascorbate peroxidase (EC 1.11.1.11) in mustard seedling cotyledons by phytochrome and photooxidative treatments (1992)
    Springer
    Planta 186 (1992), S. 600-608 
    Details
    ISSN: 1432-2048
    Keywords: Active oxygen ; Ascorbate peroxidase (isoforms) ; Peroxidase, ascorbate specific ; Photooxidation ; Phytochrome ; Sinapis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In photosynthetic cells the plastidic ascorbate-glutathione pathway is considered the major sequence involved in the elimination of active oxygen species. Ascorbate peroxidase (APO; EC 1.11.1.11) is an essential constituent of this pathway. In the present paper control of the appearance of APO was studied in the cotyledons of mustard (Sinapis alba L.) seedlings with the following results: (i) Two isoforms of APO (APO I, APO II) could be separated by anion-exchange chromatography; APO I is a plastidic protein, while APO II is extraplastidic, very probably cytosolic. (ii) The appearance of APO is regulated by light via phytochrome. This control is observed with both isoforms. Moreover, a strong positive control over APO II appearance (very probably over APO II synthesis) is exerted by photooxidative treatment of the plastids. (iii) Additional synthesis of extraplastidic APO II is induced by a signal created by intraplastidic pigment-photosensitized oxidative stress. The response is obligatorily oxygen-dependent and abolished by quenchers of singlet oxygen such as α-tocopherol and p-benzoquinone. (iv) A short-term (4 h) photooxidative treatment suffices to saturate the signal. Signal transduction cannot be abolished or diminished by replacing the plants in non-photooxidizing conditions. Several observations indicate that control of APO synthesis by active oxygen is not an experimental artifact but a natural phenomenon.
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    Distribution of phytochrome and chlorophyll-a/b-binding-protein mRNAs in etiolated Avena seedlings (1992)
    Springer
    Planta 187 (1992), S. 532-536 
    Details
    ISSN: 1432-2048
    Keywords: Avena (phytochrome) ; Chlorophyll-a/bbinding protein ; Light regulation ; mRNA localization ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In 4-d-old dark-grown oat (Avena sativa L.) seedlings, the majority of the type-I-phytochrome (phyA) mRNA was found within 10 mm of the tip of the coleoptile sheath and in the mesocotyl node; almost none was detected in the enclosed primary leaf. In contrast, chlorophyll-a/b-binding-protein (cab) mRNAs were found almost exclusively in the enclosed primary leaf and were barely detectable in total-RNA samples from the coleoptile sheath or mesocotyl node of red-light-treated etiolated seedlings. Separated, dark-grown primary leaves responded to a red-light treatment by increasing cab-mRNA abundance in the absence of the coleoptile sheath or mesocotyl node tissues.
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    Spectral-dependence of light-inhibited hypocotyl elongation in photomorphogenic mutants of Arabidopsis: evidence for a UV-A photosensor (1992)
    Springer
    Planta 188 (1992), S. 106-114 
    Details
    ISSN: 1432-2048
    Keywords: Arabidopsis ; Photomorphogenesis ; Blue/UV-A light ; Hypocotyl elongation ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photon fluence rate-response curves at different wavelengths were generated for the light-induced inhibition of hypocotyl elongation in seedlings of wildtype and photomorphogenic mutants of Arabidopsis thaliana. (L.) Heynh. Treatment of wild-type seedlings with continuous low-fluence-rate light (〈 1.0 μmol photons · m−2 · s−1) induced some inhibition of hypocotyl elongation at all wavelengths tested, with maximum inhibition in blue light. At higher fluence rates, inhibition reached a maximum of 70–80% in UV-A, blue, and far-red light. Fluence rate-response curves for seedlings of blu1, a blue light-response mutant, showed a specific reduction in their response to blue light, but their response to UV-A, red, and far-red light was similar to that in wild-type seedlings. In contrast, the phytochromedeficient mutant hy6 showed a loss of response to lowfluence-rate light at all wavelengths, as well as to highfluence-rate far-red light. However, hy6 seedlings retained sensitivity to high-fluence-rate blue and UV-A light. The data support the conclusion that blue-lightand phytochrome-dependent photosensory systems regulate hypocotyl elongation independently and in an additive manner. Furthermore, hypocotyl inhibition in wild-type, blul, hy6 and blul-hy6 double mutants was indistinguishable in UV-A light, whereas marked differences were observed at other wavelengths, indicating the involvement of a third photosensory system with an absorption maximum in the UV-A.
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    Photoinduction of formation of circular structures by microfilaments on chloroplasts during intracellular orientation in protonemal cells of the fernAdiantum capillus-veneris (1992)
    Springer
    Protoplasma 167 (1992), S. 97-107 
    Details
    ISSN: 1615-6102
    Keywords: Blue-light response ; Chloroplast photoorientation ; Fern protonema ; Microfilament ; Phytochrome ; Rhodamine-phalloidin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Changes in the organization of cortical actin microfilaments during phytochrome-mediated and blue light-induced photoorientation of chloroplasts were investigated by rhodamine-phalloidin staining in protonemal cells of the fernAdiantum capillusveneris. Low- and high-fluence rate responses were induced by partial irradiation of individual cells with a microbeam of 20 μm in width. In the low-fluence rate responses to red and blue light, a circular structure composed of microfilaments was induced on the chloroplast concentrated in the irradiated region, on the side facing the plasma membrane, as already reported in the case of the low-fluence rate response induced by polarized red or blue light. Such a structure was not observed on the chloroplasts located far from the microbeam. Time-course studies revealed that the structure was induced after the chloroplasts gathered in the illuminated region and that the structure disappeared before chloroplasts moved out of this region when the microbeam was turned off. In the high-fluence rate response to blue light, chloroplasts avoided the irradiated site but accumulated in the shaded area adjacent the edges of microbeam. The circular structure made of microfilaments was also observed on the chloroplasts gathered in the area and it showed the same behavior with respect to its appearance and disappearance during a light/dark regime as in the case of the low-fluence rate response. However, no such circular structure was observed in the high-fluence rate response to red light, in which case the chloroplasts also avoided the illuminated region but no accumulation in the adjacent areas was induced. These results indicate that the circular structure composed of microfilaments may play a role in the anchorage of the chloroplast during intracellular photo-orientation.
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    URL: http://dx.doi.org/10.1007/BF01353585
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    Reorganization of the cortical cytoskeleton in tip-growing fern protonemal cells during phytochrome-mediated phototropism and blue light-induced apical swelling (1992)
    Springer
    Protoplasma 166 (1992), S. 35-41 
    Details
    ISSN: 1615-6102
    Keywords: Adiantum capillus-veneris ; Blue light response ; Microfilament ; Microtubule ; Phytochrome ; Protonema
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Circular arrays of cortical microtubules (MTs) and microfilaments (MFs) are found in the subapical region of tip-growing protonemal cells of the fernAdiantum capillus-veneris. Reorganization of the two cytoskeletal structures during phytochrome-mediated phototropism and blue light-induced apical swelling was investigated by double-staining of MTs and MFs with rhodaminephalloidin and an indirect immunofluorescence method with tubulinspecific antibody. Before any growth responses were detectable, the MF and MT structures were reorganized according to similar patterns in both photoresponses, that is, oblique orientation and transient disappearance of the structures occurred during the phototropic response, and the disappearance of the structures occurred during apical swelling. The reorganization of MF structures clearly preceded that of the MT structures in the phototropic response. In the case of apical swelling, both types of circular array disappeared with an almost identical time course. These results provide evidence for the significant role of the circular organization of MFs as well as of MTs, in the light-induced growth responses of tip-growing fern protonemal cells. Possible roles of the circular array of MFs in the regulation of tip growth are discussed.
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    URL: http://dx.doi.org/10.1007/BF01320140
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    On the opportunity cost of the photosynthate invested in stem elongation reactions mediated by phytochrome (1991)
    Springer
    Oecologia 86 (1991), S. 561-567 
    Details
    ISSN: 1432-1939
    Keywords: Canopies ; Competition ; Light quality ; Photosynthate partitioning ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Seedlings of shade-intolerant species react to alterations of the light climate caused by their neighbors with morphological changes that may influence the pattern of resource acquisition and utilization at the whole-canopy level. One such change, the increased stem elongation rate that is triggered by low red (R, 660 nm) to far-red (FR, 730 nm) ratios (R:FR) in dense canopies, might reduce the amount of assimilates available for leaf area expansion or root growth, and in that way affect resource capture by the canopy. We have tested this hypothesis by comparing the growth of both isolated individuals and canopies of the weed Amaranthus quitensis under conditions differing only in the spectral distribution of the incident light. When canopies received the full spectrum of sunlight, the stems were a large proportion (40–57%) of total biomass. Filtering the FR waveband (and hence raising the R:FR ratio to eliminate the neighbors' proximity-signal) resulted in shorter canopies with lighter stems. However, the growth of leaves and roots was not promoted by this treatment, indicating that the opportunity cost of the assimilates invested in the stems was nil or very small. Filtering the FR had no effect on biomass accumulation when plants were grown as isolated individuals. The higher growth of the canopics under full spectrum could be due to a higher light interception or to a higher efficiency of light conversion into biomass. The first possibility is weakened by the observation that filtering the FR had no effect on the dynamics of soil covering by the crops. The second is indirectly strengthened by results of an experiment with isolated plants showing that stem elongation, stem growth, and total plant biomass can be increased by reducing the flux of R light received by the stems without affecting the light climate of the leaves. Further work is needed to distinguish between these two possibilities; whatever the cause, our results show that the elongation responses to decreased R:FR may lead to a net increase in canopy productivity, and do not necessarily have a negative impact on the growth of resource-harvesting organs.
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    URL: http://dx.doi.org/10.1007/BF00318323
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    Coaction of blue/ultraviolet-A light and light absorbed by phytochrome in controlling the appearance of ferredoxin-dependent glutamate synthase in the Scots pine (Pinus sylvestris L.) seedling (1991)
    Springer
    Planta 183 (1991), S. 374-380 
    Details
    ISSN: 1432-2048
    Keywords: Cryptochrome ; Glutamate synthase (Fd-GOGAT) ; Nitrate ; Photoreceptor (coaction of blue/UV-A light and phytochrome) ; Phytochrome ; Pinus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The appearance of NADH- and ferredoxin (Fd)-dependent glutamate synthases (GOGATs) was investigated in the major organs (roots, hypocotyl and cotyledonary whorl) of the Scots pine seedling. It was found that cytosolic NADH-GOGAT (EC 1.4.1.14) dropped to a low level during the experimental period (from 4 to 12 d after sowing) and was not significantly affected by light. On the other hand, plastidic Fd-GOGAT (EC 1.4.7.1) increased strongly in response to light. Whereas similar amounts of NADH-GOGAT were found in the different organs, Fd-GOGAT was mainly found in the cotyledons even in the presence of nitrate. Protein chromatography revealed only a single Fd-GOGAT peak. No isoforms were detected. Experiments to investigate regulation of the appearance of Fd-GOGAT in the cotyledonary whorl yielded the following results: (i) In darkness, neither nitrate (15 mM KNO3) nor ammonium (15 mM NH4Cl) had an effect on the appearance of Fd-GOGAT. In the light, nitrate stimulated Fd-GOGAT activity by 30% whereas ammonium had no effect. The major controlling factor is light. (ii) The action of long-term white light (100 W · m−2) could be replaced quantitatively by blue light (B, 10 W · m−2). Since the action of long-term far-red light was very weak, operation of the ‘High Irradiance Reaction’ of phytochrome is excluded. On the other hand, light-pulse experiments with dark-grown seedlings showed the involvement of phytochrome. (iii) Red light, operating via phytochrome, could fully replace B, but only up to 10 d after sowing. Thereafter, there was an absolute requirement for B for a further increase in the enzyme level. It appears that the operation of phytochrome was replaced by the operation of cryptochrome (B/UV-A photoreceptor). (iv) However, dichromatic experiments (simultaneous treatment of the seedlings with two light beams to vary the level of the far-red-absorbing form of phytochrome (Pfr) in blue light) showed that B does not affect enzyme appearance if the Pfr level is low. It is concluded that B is required to maintain responsiveness of Fd-GOGAT synthesis to phytochrome (Pfr) beyond 10 d after sowing.
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    URL: http://dx.doi.org/10.1007/BF00197736
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    Coaction of light, nitrate and a plastidic factor in controlling nitrite-reductase gene expression in spinach (1991)
    Springer
    Planta 184 (1991), S. 74-80 
    Details
    ISSN: 1432-2048
    Keywords: Gene expression ; Nitrate ; Nitrite reductase (control) ; Phytochrome ; Spinacia (nitrite reductasegene expression)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract It is well established that nitrite reductase (NIR; EC 1.7.7.1) a key enzyme of nitrate reduction — is “induced” by nitrate and light. In the present study with the spinach (Spinacia oleracea L.) seedling the dependency of NIR appearance on nitrate, light and a ‘plastidic factor’ was investigated to establish the nature of the coaction between these controlling factors. A cDNA clone coding for spinach NIR was available as a probe. The major results we have obtained are the following: (i) The light effect on the appearance of NIR activity occurs through phytochrome. No specific bluelight effect is involved, (ii) Immunotitration data indicate that light affects the appearance of NIR by inducing the de-novo synthesis of the NIR protein, (iii) A multiplicative relationship exists between the action of nitrate and light on NIR appearance. This indicates that the actions of light and nitrate are indeed independent of each other but that both factors operate on the same causal sequence, (iv) Anion-exchange chromatography revealed only a single form of NIR in spinach. Experiments involving plastid photooxidation indicate that this NIR is exclusively plastidic. (v) Northern blot analysis of NIR mRNA showed a strong increase of the steady-state level in the presence of nitrate whereas light had no effect; NIR mRNA was almost undetectable when the plastids were damaged by photooxidation. It is concluded that NIR gene expression in spinach requires positive control by a ‘plastidic factor’. Moreover, nitrate exerts a coarse control at the mRNA level whereas fine tuning of NIR protein synthesis is post-transcriptional and is exerted by light, operating via phytochrome.
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    URL: http://dx.doi.org/10.1007/BF00208239
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    Photoresponses of transgenic tobacco plants expressing an oat phytochrome gene (1991)
    Springer
    Planta 185 (1991), S. 162-170 
    Details
    ISSN: 1432-2048
    Keywords: Gene (oat phyA) ; Light (red ∶ far red ratio) ; Nicotiana (transgenic, photoresponses) ; Phytochrome ; gene (in transgenic plant)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The physiological responses of transgenic tobacco (Nicotiana tabacum L.) plants that express high levels of an introduced oat (Avena sativa L.) phytochrome (phyA) gene to various light treatments are compared with those of wild-type (WT) plants. Seeds, etiolated seedlings, and light-grown plants from a homozygous transgenic tobacco line (9A4) constructed by Keller et al. (EMBO J, 8, 1005–1012, 1989) were treated with red (R), far-red (FR), or white light (WL) with or without supplemental FR light, revealing major perturbations of the normal photobiological responses. White light stimulated germination of both WT and transgenic seed, but addition of FR to the WL treatment suppressed germination. In the WT, all fluence rates tested inhibited germination, but in the transgenics, reduction effluence rate partially relieved germination from the FR-mediated inhibition. It is suggested that the higher absolute levels of the FR-absorbing form of phytochrome (Pfr) in the irradiated transgenics, compared to the WT, may be responsible for the reduced FR-mediated inhibition of germination in the former. Hypocotyl extension of dark-grown seedlings of both WT and transgenic lines was inhibited by continuous R or FR irradiation, typical of the high-irradiance response (HIR). After 2 d of de-etiolation in WL, the WT seedlings had lost the FR-mediated inhibition of hypocotyl extension, whereas it was retained in the transgenics. The FR-mediated inhibition of hypocotyl extension in the transgenic seedlings after de-etiolation may reflect the persistence of an, FR-HIR response mediated by the overexpressed oat PhyA phytochrome. Light-grown WT seedlings exhibited typical shade-avoidance responses when treated with WL supplemented with high levels of FR radiation. Internode and petiole extension rates were markedly increased, and the chlorophyll a∶b ratio decreased, in the low-R: FR treatment. The transgenics, however, showed no increases in extension growth under low-R: FR treatments, and at low fluence rates both internode and petiole extension rates were significantly decreased by low R ∶ FR. Interpretation of these data is difficult. The depression of the chlorophyll a∶b ratio by low R ∶ FR was identical in WT and transgenic plants, indicating that not all shade-avoidance responses of light-grown plants were disrupted by the over-expression of the introduced oat phyA gene. The results are discussed in relation to the proposal that different members of the phytochrome family may have different physiological roles.
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    URL: http://dx.doi.org/10.1007/BF00194057
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    Photophysiology of turion germination in Spirodela polyrhiza (L.) Schleiden VIII. Calcium dependence and β-amylase activity (1991)
    Springer
    Planta 186 (1991), S. 81-87 
    Details
    ISSN: 1432-2048
    Keywords: β-Amylase ; Calcium ; Germination (turions) ; Phytochrome ; Signal transduction ; Turion ; Spirodela
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Red-light-induced germination (via phytochrome) of turions of Spirodela polyrhiza (L.) Schleiden, strain SJ, showed an absolute requirement for exogenously applied calcium (Appenroth et al. 1990b, Biochem. Physiol. Pflanzen 186, 209–219). With calcium step-up experiments (from 0.9 μM to 1 mM Ca2+) the influence of Ca2+ on the escape from far-red-light reversibility was investigated. Delaying the time of Ca2+ application after the red light pulse resulted in an increased reversibility. This confirmed that the calcium-requiring phase is within the phytochrome-dependent period. Ten days after a red light pulse was applied the activity of β-amylase (EC 3.2.1.2) was increased about tenfold. The starting point was similar in the germination and enzymatic responses, but half-maximal response times according to the Mitscherlich function (2.5 d and 6.9 d, respectively) and times of saturation (about 6 d and 9 d, respectively) were different. Increase of β-amylase activity was completely inhibited by irradiation with far-red light (demonstrating phytochrome as the photoreceptor), as well as by inhibitors of translation (cycloheximide, puromycin) and transcription (cordycepin). Once formed, the active enzyme protein was stable for at least 4 d after cycloheximide application. After application of cordycepin a small amount of translation activity was detected until complete inhibition was reached after 2 d. This phytochrome-modulated, de-novo synthesis of β-amylase was only slightly dependent on exogenous Ca2+. Therefore, it can be concluded that the phytochrome-mediated signal-transduction chain branches either in its reversible part or as a consequence of diversity of the primary phytochrome reaction.
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    URL: http://dx.doi.org/10.1007/BF00201501
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    Cyclic temperature treatments of dark-grown pea seedlings induce a rise in specific transcript levels of light-regulated genes related to photomorphogenesis (1991)
    Springer
    Molecular genetics and genomics 225 (1991), S. 468-473 
    Details
    ISSN: 1617-4623
    Keywords: Circadian rhythm ; Heat shock ; Lightinduction ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Dark-grown pea seedlings exposed to cyclic heat shocks or daily temperature changes undergo a morphogenetic development similar to that induced by far red light. The morphological changes observed include expansion of the leaves, shortening of the stems and opening of the hooks. Compared with control etioplasts, plastids of heat-treated seedlings are as large as fully mature chloroplasts and contain well developed, unstacked membranes. These morphogenetic changes correlate with elevated levels of SSU and LHCP mRNAs which, under these conditions, fluctuate in a circadian manner. In contrast, the ELIP mRNA remains under strict light control and shows circadian fluctuations only if the plants are exposed to a short period of illumination. We propose that periodic temperature changes, like light treatment, might serve as a ‘Zeitgeber’ signal for circadian rhythm. The data indicate a correlation between the existence of circadian oscillations and morphogenetic development.
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    phyB is evolutionarily conserved and constitutively expressed in rice seedling shoots (1991)
    Springer
    Molecular genetics and genomics 225 (1991), S. 305-313 
    Details
    ISSN: 1617-4623
    Keywords: Oryza sativa ; Phytochrome ; Multigene family ; Gene sequence conservation ; Gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Southern blot analysis indicates that the rice genome contains single copies of genes encoding type A (phyA) and type B (phyB) phytochromes. We have isolated overlapping cDNA and genomic clones encoding the entire phyB polypeptide. This monocot sequence is more closely related to phyB from the dicot, Arabidopsis (73% amino acid sequence identity), than it is to the phyA gene in the rice genome (50% identity). These data support the proposal that phyA and phyB subfamilies diverged early in plant evolution and that subsequent divergence accompanied the evolution of monocots and dicots. Moreover, since rice and Arabidopsis phyB polypeptides are more closely related to one another (73% identity) than are monocot and dicot phyA sequences (63–65% identity), it appears that phyB has evolved more slowly than phyA. Sequence conservation between phyA and phyB is greatest in a central core region surrounding the chromophore attachment site, and least toward the amino-terminal and carboxy-terminal ends of the polypeptides, although hydropathy analysis suggests that the overall structure of the two phytochromes has been conserved. Gene-specific Northern blot analysis indicates that, whereas phyA is negatively regulated by phytochrome in rice seedling shoots in the manner typical of monocots, phyB is constitutively expressed irrespective of light treatment. In consequence, phyA and phyB transcripts are equally abundant in fully green tissue. Since Arabidopsis phyB mRNA levels are also unaffected by light, the present results suggest that this mode of regulation is evolutionarily conserved among phyB genes, perhaps reflecting differences in the functional roles of the different phytochrome subfamilies.
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    Influence of acetylcholine agonists and antagonists on the swelling of etiolated wheat (Triticum aestivum L.) mesophyll protoplasts (1990)
    Springer
    Planta 182 (1990), S. 473-479 
    Details
    ISSN: 1432-2048
    Keywords: Acetylcholine (agonist, antagonist) ; Phytochrome ; Protoplast (acetylcholine, swelling) ; Triticum (protoplast swelling)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Etiolated wheat (Triticum aestivum L.) mesophyll protoplasts swell within 30 min in darkness after a red light (R) pulse or addition of acetylcholine (ACh), if 0.5 mM CaCl2 is present in the medium. In addition, ACh is also able to induce swelling in the presence of both 0.1 mM KCl or NaCl. Besides ACh, only carbamylcholine out of the choline derivatives tested was active in induction of swelling in the presence of K+ or Na+. The K+/Na+-dependent ACh-induced protoplast swelling was nullified by a ‘calmodulin inhibitor’, but not by Ca2+-channel blockers, Li+ or VO 4 3- . The antagonists atropine (of muscarine-sensitive ACh receptors, mAChRs) andd-tubocurarine (of nicotine-sensitive ACh receptors, nAChRs) nullified the Ca2+ — and the K+/Na+-dependent protoplast swelling responses, respectively, while having no effect on the Ca2+-dependent R-induced swelling response. Moreover, muscarine and nicotine mimicked ACh in the Ca2+- and K+/Na+-dependent swelling responses respectively. Just as is the case in animal cells, the proposed mAChRs appear to be associated with a phosphatidylinositol-dependent pathway, whereas the proposed nAChRs are phosphatidylinositol independent. Similarity between the action of ACh via the proposed mChRs and R via phytochrome in protoplast swelling indicates they share in common signal-transduction pathway.
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    URL: http://dx.doi.org/10.1007/BF02341020
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    How portulaca seedlings avoid their neighbours (1990)
    Springer
    Oecologia 82 (1990), S. 490-493 
    Details
    ISSN: 1432-1939
    Keywords: Developmental plasticity ; Environmental signals ; Far-red light ; Phytochrome ; Plant competition ; Portulaca oleracea L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Portulaca oleracea L. seedlings do not develop in the direction of neighbours, even when these neighbours are small and distant. Neighbouring plants could be simulated by small rectangles of a plastic that resembled leaves in its spectral characteristics. Unlike seedlings, mature plants did not respond to objects that do not influence photosynthetic light. When light of equal intensity was received from all directions, Portulaca seedlings avoided the direction with higher far-red light. Portulaca is thus able to use spectral composition and direction of light as clues for the probability of the direction of future shade.
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    Ecological significance of light controlled seed germination in two contrasting tropical habitats (1990)
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    Oecologia 83 (1990), S. 171-175 
    Details
    ISSN: 1432-1939
    Keywords: Buddleja ; Cecropia ; Chenopodium ; Phytochrome ; Piper
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effects of temperature, photoperiod, phytochrome photoreversion and the response to a R/FR ratio gradient were investigated in seeds of four species from two contrasting tropical habitats; two species from a rain forest (Cecropia obtusifolia and Piper umbellatum) and two from a high altitude lava field covered by low vegetation (Buddleja cordata and Chenopodium ambrosioides). In the rain forest seed species the photoblastic response seems to be adapted to light quality changes due to canopy destruction, on the other hand, the lava field seed species seem to be adapted to instantaneous light stimulus such as would be produced by the sudden exposure of a buried seed to the soil surface light environment.
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    Coaction of blue/ultraviolet-A light and light absorbed by phytochrome in controlling growth of pine (Pinus sylestris L.) seedlings (1990)
    Springer
    Planta 180 (1990), S. 212-216 
    Details
    ISSN: 1432-2048
    Keywords: Coaction of photoreceptors ; Cryptochrome ; Phytochrome ; Pinus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photomorphogenesis is a conspicuous feature in conifers. In the case of the shade-intolerant Scots pine (Pinus sylvestris L.), control of stem growth by light is well expressed at the seedling stage and can readily be studied. The present data show that hypocotyl growth is controlled by the far-red-absorbing form of phytochrome (Pfr). However, the Scots pine seedling requires blue or ultraviolet (UV-A) light to become fully responsive to Pfr. Blue/UV-A light has no direct effect on hypocotyl growth and its action appears to be limited to establishing the responsiveness of the seedling to Pfr. This type of coaction between phytochrome and blue/UV-A light has been observed previously in a number of angiosperm seedlings. With regard to the ‘high irradiance reaction’ of phytochrome in long-term far-red light the pine seedling deviates totally from what has been observed in etiolated angiosperms since continuous far-red light has no effect on stem growth.
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    Appearance of nitrite-reductase mRNA in mustard seedling cotyledons is regulated by phytochrome (1990)
    Springer
    Planta 181 (1990), S. 327-334 
    Details
    ISSN: 1432-2048
    Keywords: Gene expression (control points) ; Nitrate ; Nitrite reductase ; Phytochrome ; Sinapis (phytochrome)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrate reductase (NR, EC 1.6.6.1) and nitrite reductase (NIR, EC 1.7.7.1) are the key enzymes of nitrate reduction. It is well established that the appearance of these enzymes is “induced” by nitrate, and it is generally believed that NR is cytosolic while NIR is plastidic. In mustard (Sinapis alba L.) cotyledons we observed two isoforms of NIR (NIR1 and NIR2) using a chromato-focusing technique. Only one of them (NIR2) disappeared when the plastids were damaged by photooxidation in the presence of Norflurazon. It is concluded that NIR2 is plastidic while NIR1 is extraplastidic and not affected by photooxidation of the plastids. Both isoforms appear to have the same molecular weight (60 kilodaltons, kDa). Two distinct translation products which could be immunoprecipitated with NIR antiserum produced against total NIR from mustard were observed which differed slightly in molecular weight (60 versus 63 kDa). The 63-kDa polypeptide was considered to be the precursor of NIR2. While synthesis of NIR protein depended largely on nitrate, the levels of in-vitro-translatable NIR mRNAs were found to be either independent of nitrate and light (NIR1) or controlled by phytochrome only (NIR2). It appears that phytochrome strongly stimulates the level of mRNA while significant enzyme synthesis (NIR2) takes place only in the presence of relatively large amounts of nitrate. Since an increased enzyme level was strictly correlated with an increase of immunoresponsive NIR protein it is improbable that activation of a precursor plays a role. Rather, it is concluded that, in situ, nitrate controls translation.
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    Effect of nitrate, ammonium, light and a plastidic factor on the appearance of multiple forms of nitrate reductase in mustard (Sinapis alba L.) cotyledons (1989)
    Springer
    Planta 177 (1989), S. 74-83 
    Details
    ISSN: 1432-2048
    Keywords: Ammonium toxicity ; Nitrate reductase (multiple forms) ; Phytochrome ; Plastidic factor ; Sinapis (nitrate reductase)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In mustard (Sinapis alba L.) cotyledons, four different forms of nitrate reductase (NR) can be separated by anion-exchange chromatography. Two of these forms (NR1 and NR2) appear in the presence of NO 3 - while the other two (NR3 and NR4) appear as a response to the application of NH 4 + as the sole nitrogen source. In the presence of NH4NO3, NR3 appears to be superimposed on nitrate-induced NR1 and NR2 while the NH 4 + -induced appearance of NR4 is totally abolished in the presence of equimolar amounts of NO 3 - . The appearance of NR1, NR2 and NR3 is strongly stimulated by red light pulses which operate via the far-red-absorbing form of phytochrome (Pfr), whereas the appearance of NR4 requires continuous light (likewise operating through pytochrome). Continuous red light is more effective in this case than continuous far-red light. Analysis of the data shows that the mode of action of phytochrome (Pfr) is the same in the case of the appearances of NR1 and NR2, whereas it is quantitatively different in the case of NR3 and totally different in that of NR4. A ‘plastidic factor’ has previously been postulated to be obligatorily involved in the transcriptional control of nuclear genes encoding for proteins destined for the chloroplast. Photooxidative damage of the plastid is postulated to destroy the ability of the organelle to produce this signal. If the plastids are damaged by photooxidation, the action of nitrate and phytochrome on the appearance of NR is abolished. The plant cell regulates the appearance of nitrate-induced NR, which is cytosolic, as if it were a plastidic protein. The appearance of NR3 depends on the plastidic factor in principally the same way as that of NR1 and NR2 whereas NR4 is totally independent of the plastidic factor. The data document particular kinds of interaction between controlling factors (light, nitrate, ammonium, plastidic factor) which affect gene expression in plants. These intricacies of regulation have so far not been considered in molecular studies on NR-gene expression.
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    Effects of calcium channel blockers and DCMU on motility and the photophobic response of Gyrodinium dorsum (1989)
    Springer
    Archives of microbiology 151 (1989), S. 187-190 
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    ISSN: 1432-072X
    Keywords: Calcium ; Calcium channel blocker ; Dinoflagellate ; Gyrodinium dorsum ; Motility ; Phytochrome ; Stop-response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of the calcium channel blockers, verapamil, diltiazem and lanthanum ions and the Ca2+ dependency on motility as well as the photophobic response (stop-response) of Gyrodinium dorsum were studied. At Ca2+ concentrations below 10-3 M, motility was inhibited. La3+ inhibits the stop-response, in contrast to verapamil and diltiazem. The only calcium channel blocker that increased the amount of non-motile cells was verapamil. The results indicate that motility are Ca2+ dependent and that the stop-responses of G. dorsum could be affected by extracellular Ca2+. Effects of the photosythesis inhibitor (DCMU) on the stop-response was also determined. With background light of different wavelength (614, 658 and 686 nm) the stop-response increased. DCMU inhibited this effect of background light. Negative results with the monoclonal antibody Pea-25 directed to phytochrome and the results with DCMU, indicate that the stop-response of G. dorsum is coupled to photosynthesis rather than to a phytochrome-like pigment. Oxygen evolution, but not cell movement, was completely inhibited by 10-6 M DCMU.
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    URL: http://dx.doi.org/10.1007/BF00413128
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    Regulation of the appearance of glutamine synthetase in mustard (Sinapis alba L.) cotyledons by light, nitrate and ammonium (1989)
    Springer
    Planta 177 (1989), S. 526-534 
    Details
    ISSN: 1432-2048
    Keywords: Ammonium assimilation ; Glutamine synthetase ; Nitrate ; Phytochrome ; Sinapis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During transformation of mustard seedlings cotyledons from storage organs to photosynthetically competent leaves, a process which occurs during the first 4 d after sowing, total glutamine-synthetase (GS, EC 6.3.1.2) activity increases from zero to the high level usually observed in green leaves. In the present study we have used ion-exchange chromatography to separate possible isoforms of GS during the development of the cotyledons. The approach failed since we could only detect a single form of GS, presumably plastidic GS, under all circumstances tested. The technique of selective photooxidative destruction of plastids in situ was applied to solve the problem of GS localization. It was inferred from the data that the GS as detected by ion-exchange chromatography is plastidic GS. The regulatory role, if any, of light, nitrate and ammonium in the process of the appearance of GS in the developing cotyledons was investigated. The results show that nitrate and ammonium play only minor roles. Light, operating via phytochrome, is the major regulatory factor.
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    URL: http://dx.doi.org/10.1007/BF00392621
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    Characterization of a protein-kinase activity associated with phytochrome from etiolated oat (Avena sativa L.) seedlings (1989)
    Springer
    Planta 178 (1989), S. 199-206 
    Details
    ISSN: 1432-2048
    Keywords: Avena ; Calmodulin ; Etiolated seedling ; Phytochrome ; Protein kinase ; (ATP-dependent)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A protein-kinase activity which is co-purified with phytochrome from etiolated oat seedlings was investigated in some detail. Whereas phytochrome was always phosphorylated in solution (together with some contaminating protein bands), radioactive phosphate was not found in the phytochrome band after native gel electrophoresis and incubation of the entire gel with labeled ATP. Since protein kinases are usually autophosphorylated under these conditions, the result shows that the kinase activity does not reside in the phytochrome molecule itself. Radioactivity was exclusively detected in a band with the apparent molecular weight 450 kDa; sodium-dodecyl-sulfate gel electrophoresis revealed an apparent molecular weight of 60 kDa for the phosphorylated subunit. The N-terminal amino-acid sequence A L E S A G K Q L V P W was determined for this subunit which is a potential candidate for the protein kinase. The optimum conditions (pH, metal ion concentration) and kinetics of the phosphorylation reaction were determined. The presumed connection between proteinkinase activity and the signal chain leading from the far-red-absorbing form of phytochrome to physiological responses still awaits elucidation.
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    URL: http://dx.doi.org/10.1007/BF00393195
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    Isolation and characterization of a maize chlorophyll a/b binding protein gene that produces high levels of mRNA in the dark (1989)
    Springer
    Molecular genetics and genomics 215 (1989), S. 431-440 
    Details
    ISSN: 1617-4623
    Keywords: Zeamays ; Phytochrome ; Light-regulated gene expression ; Light harvesting chlorophyll a/b binding protein ; Chlorophyll a/b binding protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A cDNA libary prepared using mRNA isolated from red-light irradiated maize seedlings was screened by a difference procedure for clones that represent red-light regulated mRNA. Two such clones were found to represent mRNA for a chlorophyll a/b binding protein (CAB), and one of these (pAB1084) was used to screen a maize genomic library. One positive genomic clone (λAB1084) was isolated and sequenced. The gene represented by λAB1084, which we designate maize cab-1, contains extensive nucleotide homology within its protein coding region to CAB genes from other species. The boundaries of the transcribed region of the cab-1 gene were determined by S1 nuclease mapping. The 5′ terminus of cab-1 mRNA is located 52–54 nucleotides (nt) upstream of the translation start site and 34 nt downstream of a TATA box. As in the case of petunia CAB genes, several poly(A) addition sites are present in mRNA from the cab-1 gene. The 5′ flanking DNA of cab-1 contains sequences related to elements that have been implicated in the light-regulated expression of CAB and rccS genes in other plant systems. Quantitative Northern blot hybridization analysis using a gene specific probe for cab-1 indicates that the mRNA for this gene is present at 0.4% of the total mRNA and up to 80% of the total CAB mRNA in the leaves of dark-grown seedlings. In consequence, although the degree of up-regulation by white light is only moderate (3- to 6-fold), cab-1 transcripts account for approximately 2% of the mRNA in the leaves of light-grown seedlings.
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    URL: http://dx.doi.org/10.1007/BF00427040
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    Photoinduction of circular F-actin on chloroplast in a fern protonemal cell (1989)
    Springer
    Protoplasma 151 (1989), S. 171-174 
    Details
    ISSN: 1615-6102
    Keywords: Blue light receptor ; Chloroplast movement ; F-actin ; Fern protonema ; Phytochrome ; Rhodamine-phalloidin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Circular F-actin on a photooriented chloroplast was observed by rhodamine-phalloidin staining in the fernAdiantum protonemal cells in which phytochrome- or blue light receptor-mediated intracellular photoorientation of chloroplasts was induced. The circular structure located along the edge of chloroplast on the side facing the plasma membrane but not on the opposite side. Most of the chloroplasts in protonemal cell have dumbbell-shape and the circular ring-like structure was found on each half of the dumbbell. The structure was not observed in the cells which were kept in the dark, indicating the change of F-actin organization by the light condition. Possible role of the structure on the anchorage of chloroplast in its intracellular photoorientation was discussed.
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    URL: http://dx.doi.org/10.1007/BF01403456
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    Physiological characterization of a plastidic signal required for nitrate-induced appearance of nitrate and nitrite reductases (1988)
    Springer
    Planta 174 (1988), S. 75-83 
    Details
    ISSN: 1432-2048
    Keywords: Nitrate reductase ; Nitrite reductase ; Phytochrome ; Plastidic signal ; Sinapis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We compared the response of NO 3 - -induced nitrate-reductase (NR) and nitrite-reductase (NIR) levels in virtually carotenoid-free far-red-light-grown mustard (Sinapis alba L.) cotyledons following a photooxidative treatment of the plastids. The cytosolic localization of NR and the plastidic localization of NIR were confirmed with this approach. Emphasis was on a plastidic factor previously postulated to be involved obligatorily in the transcriptional control of nuclear genes coding for proteins destined for the chloroplast. Photooxidative damage of the plastid would be to destroy the ability of the organelle to send off this signal. Dependency of NIR and NR induction by NO 3 - on the plastidic factor is described in detail, and it is concluded that requirement for the plastidic factor is relatively high in the case of NR while factor requirement to allow induction is low in the case of NIR. The data indicate that in the case of NIR the photooxidative damage done to the plastid also affects accumulation of the enzyme directly. Since this effect is absent in the case of cytosolic NR, induction of NR is a particularly suitable system for further molecular studies of the plastidic factor and its mode of action.
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    URL: http://dx.doi.org/10.1007/BF00394876
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    Effect of light and gibberellic acid on cell division in the first foliage leaf of durum wheat (Triticum durum Desf.) (1988)
    Springer
    Planta 173 (1988), S. 257-262 
    Details
    ISSN: 1432-2048
    Keywords: Blue light ; Cell division (GA3 light) ; Leaf growth ; Gibberellin ; Light (GA3, cell division) ; Phytochrome ; Triticum (GA3 light)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The present paper is part of a research program which aims at a quantitative analysis of the effects of light and gibberellic acid (GA3) on growth of the first foliage leaf in durum wheat (Triticum durum Desf.). Since leaf growth is the combined result of the increase in cell number (cell division) and cell enlargement, the influence of light and GA3 treatment on cell division in the basal meristem of the first leaf in two cultivars, Cappelli and Creso, was investigated. Creso is a short-strawed cultivar carrying the Gai 1 gene which influences both plant height and insensitivity to applied GA3. Cell division, as measured by mitotic index, was similar in darkness, continuous red light and dichromatic irradiation (far-red plus red), while lower mitotic rates were observed under continuous far-red light: this indicates that the response of cell division is modulated by a high-irradiance reaction of phytochrome in both cultivars. The two cultivars showed different responses to blue light. In Cappelli, blue light and dichromatic irradiation (blue plus red) gave lower mitotic indices than the dark control, indicating the action of a specific blue-light-absorbing photoreceptor, whereas in Creso the response kinetics to all light regimes which included blue light were more complex. On the basis also of the results obtained with GA3 application in Cappelli, it appears that (i) the hormonal treatment is able to change the pattern of mitotic index only in the presence of the action of a blue-light receptor and (ii) the different responses of the two cultivars could be the result of different endogenous hormonal levels. The importance of the observations in relation to the data for first-leaf longitudinal growth reported in a previous paper (Baroncelli et al. 1984, Planta 160, 298–304) is discussed.
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    URL: http://dx.doi.org/10.1007/BF00403018
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    The effect of red and far-red light on proton secretion from mesophyll-cell protoplasts of Vicia faba L. (1988)
    Springer
    Planta 173 (1988), S. 42-45 
    Details
    ISSN: 1432-2048
    Keywords: Light (red, far red) ; Mesophyll cell protoplast ; Phytochrome ; Proton secretion ; Vicia (H+ secretion)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The influence of red and far-red irradiation on the transport of H+ and 86Rb+ through the plasmalemma was studied using parenchymal protoplasts isolated from Vicia faba leaves. The results indicate that red light stimulates H+ secretion and the uptake of 86Rb+. Moreover, it has been demonstrated that far-red irradiation acts antagonistically with respect to red light in both these processes.
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    URL: http://dx.doi.org/10.1007/BF00394485
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    Photomorphogenesis in Chenopodium album. Effects of supplementary far-red light on the kinetics of stem extension (1987)
    Springer
    Planta 172 (1987), S. 131-138 
    Details
    ISSN: 1432-2048
    Keywords: Chenopodium ; Photoperception ; Phytochrome ; Shade avoidance ; Stem extension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of far-red light given against a background of white light on the stem-extension kinetics of three-week-old, light-grown Chenopodium album seedlings were investigated. Under white light alone, the stems (cotyledon-to-apex) extended almost exactly logarithmically with time. Under these conditions the increase in log [stem length in mm] per hour was approx. 3.7·10-3, equivalent to about 1% per h during both skoto-and photoperiods. Supplementary far-red given throughout each photoperiod massively stimulated extension. The calculated logarithmic extension rate, however, slowly returned to that of the controls, following an initial large increase. This is predicted by a model in which far-red light linearly increases the extension rate of individual internodes which arise at an exponentially increasing rate. The behaviour of the model is also consistent with critical experiments in which far-red was given as a pre-treatment or transiently, as well as with other published data. Far-red stimulation of logarithmic extension rate in successive photoperiods was closely and linearly correlated with calculated phytochrome photoequilibrium. Daily short periods of supplementary far-red were especially potent in accelerating extension; the plants seemed least responsive at the end of the photoperiod.
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    URL: http://dx.doi.org/10.1007/BF00403039
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    Phytochrome action in light-grown mustard: kinetics, fluence-rate compensation and ecological significance (1987)
    Springer
    Planta 172 (1987), S. 219-229 
    Details
    ISSN: 1432-2048
    Keywords: Phytochrome ; Mustard ; Sinapis alba ; Far-red light ; Extension growth ; Light grown plants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Internode extension in young, light-grown mustard plants was measured continuously to a high degree of resolution using linear voltage displacement transducers. Plants were grown in background white light (WL) and the first internode was irradiated with supplementary far-red (FR) from fibre-optic light guides, depressing the Pfr/P (ratio of FR-absorbing form of phytochrome to total spectrophotometrically assayable phytochrome) within the internode and causing an acceleration of extension rate. The internode was sensitive to periods of FR as brief as 1 min, with a sharp increase in extension rate occurring after the return to background WL only. The mean latent period of the response to FR was approx. 10 min. Periods of FR longer than approx. 35 min caused an apparently biphasic growth response, with an initial sharp acceleration in extension rate (Phase 1) being followed by a brief deceleration and a further acceleration to a more-or-less steady elevated rate, somewhat less than the first peak (Phase 2). With such longer-term FR, extension rate decelerated upon FR switch-off after a mean lag of approx. 6 min, achieving the prestimulation extension rate within 16 min. The magnitude of the FR-induced increase in extension rate, expressed as a percentage of the rate in WL alone, was an inverse, linear function of the phytochrome photoequilibrium (i.e. Pfr/P, measured in etiolated test material irradiated under the same geometry) over the range 0.17 to 0.63. This relationship was not significantly affected by variations in backround WL fluence rate over the range 50–150 μmol·m-2·s-1 and was held both for Phase 1 and Phase 2 of the response. The data provide evidence for rapid coupling/uncoupling between phytochrome and its transduction chain in the light-grown plant and for fluence-rate compensation of the regulation of extension rate. The extensive linearity of the relationship between phytochrome photoequilibrium and proportional extension rate increment allows for fine tuning in shade avoidance. The results are discussed with respect to recent evidence on the nature of phytochrome in light-grown plants and in relation to the function of phytochrome in plants growing in the natural environment.
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    URL: http://dx.doi.org/10.1007/BF00394591
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    Signal storage in phytochrome action on nitrate-mediated induction of nitrate and nitrite reductases in mustard seedling cotyledons (1987)
    Springer
    Planta 171 (1987), S. 136-143 
    Details
    ISSN: 1432-2048
    Keywords: Nitrate reductase ; Nitrite reductase ; Phytochrome ; Signal (storage, transduction) ; Sinapis (phytochrome)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Application of nitrate leads to an induction of nitrate reductase (NR; EC 1.6.6.1) and nitrite reductase (NIR; EC 1.7.7.1) in the cotyledons of dark-grown mustard (Sinapis alba L.) seedlings, and this induction can strongly be promoted by a far-red-light pretreatment — operating through phytochrome — prior to nitrate application. This light treatment is almost ineffective — as far as enzyme appearance is concerned — if no nitrate is given. When nitrate is applied, the stored light signal potentiates the appearance of NR and NIR in darkness, even in the absence of active phytochrome, to the same extent as continuous far-red light. This action of previously stored light signal lasts for approx. 12 h. Storage of the light signal was measured for NR and NIR. The process shows enzyme-specific differences. Storage occurs in the absence as well as in the presence of nitrate, i.e. irrespective of whether or not enzyme synthesis takes place. The kinetics of signal transduction and signal storage indicate that the formation and action of the stored signal are a bypass to the process of direct signal transduction. Signal storage is possibly a means of enabling the plant to maintain the appropriate levels of NR and NIR during the dark period of the natural light/dark cycle.
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    URL: http://dx.doi.org/10.1007/BF00395077
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    Inhibition and promotion by light of the accumulation of translatable mRNA of the light-harvesting chlorophyll a/b-binding protein of photosystem II (1987)
    Springer
    Planta 172 (1987), S. 60-70 
    Details
    ISSN: 1432-2048
    Keywords: Chlorophyll (gene expression) ; Gene expression and light ; Light and gene expression ; Light-harvesting chlorophyll a/b-binding protein ; Phytochrome ; Ribulose-1.5-bisphosphate carboxylase ; Sinapis (light, mRNA)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The amount of in-vitro translatable mRNA of the light-harvesting chlorophyll a/b-binding protein (LHCP) of photosystem II strongly increases in darkness (D) after a 5-min red-light pulse while continuous illumination of mustard seedlings with far-red (FR), red or white light leads only to a slight increase in the amount of translatable LHCP-mRNA. No increase can be observed after a long-wavelength FR (RG9-light) pulse. However, a FR pretreatment prior to the RG9-light pulse strongly increase LHCP-mRNA accumulation in subsequent D. This is not observed in the case of the mRNA for the small subunit of ribulose-1.5-bisphosphate carboxylase. The increase of LHCP-mRNA in D after a FR pretreatment can be inhibited by a reillumination of the seedlings with FR. The inhibition of LHCP-mRNA accumulation during continuous illumination with FR and the strong increase in D following a FR illumination was found to be independent of chlorophyll biosynthesis since no correlation between chlorophyll biosynthesis and translatable LHCP-mRNA levels could be detected. Even strong changes in the amount of intermediates of chlorophyll biosynthesis caused by application of levulinic acid or 5-aminolevulinic acid did not affect LHCP-mRNA levels. Therefore, we conclude that the appearance of LHCP-mRNA is inhibited during continuous illumination, even though illumination leads to a storage of a light singal which promotes accumulation of translatable LHCP-mRNA in D.
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    URL: http://dx.doi.org/10.1007/BF00403029
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    Temporal and light control of plastid transcript levels for proteins involved in photosynthesis during mustard (Sinapis alba L.) seedling development (1987)
    Springer
    Planta 172 (1987), S. 393-399 
    Details
    ISSN: 1432-2048
    Keywords: Chloroplast gene expression ; Competence ; Photosynthesis ; Phytochrome ; Sinapis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Transcript levels of four plastid genes encoding constituents of the photosynthetic apparatus were assessed in cotyledons of developing mustard (Sinapis alba L.) seedlings. These genes, encoding the P700 apoproteins of photosystem I, the alpha subunit of the extrinsic CF1 moiety of the plastid ATP synthase complex, and the cytochromes f and b 6, have been localized and mapped previously on mustard chloroplast DNA (G. Dietrich and G. Link, 1985 Curr. Genet. 9, 683–692). Dot blot and Northern hybridization analysis provides evidence that in dark-grown seedlings transcript levels of all four genes rise between 30 h and 72 h after sowing and thereafter fall again, pointing to the existence of an endogenous, light-independent, developmental program. In light-grown seedlings, an additional enhancement of transcript levels beyond, the dark values becomes noticeable at approx. 30–36 h and then continues throughout the subsequent “light-responsive” phase until 96 h after sowing. This is consistent with a photoregulated modulation mechanism operating once “competence” has been reached. Enhanced transcript accumulation occurs following continuous illumination by either white light or (photosynthetically inefficient) far-red light thought to operate mainly through phytochrome. However, the degree of light enhancement for the transcript specifying the P700 apoprotiens is higher with white light than with far-red light, implying involvement of additional photoreceptor(s) mediating this response. In addition to the endogenous gross regulation and light enhancement, a fine regulation of transcript levels seems to operate, as indicated by temporal variations of two related transcripts originating from the cytochrome-f gene region. The observed developmental and photocontrolled changes in specific transcript levels for photosynthesis proteins are only reflected in part by changes in total RNA content and do not appear due to light-dark differences in plastid-DNA copy number during mustard seedling development.
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    URL: http://dx.doi.org/10.1007/BF00398669
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    Appearance of nitrite reductase in cotyledons of the mustard (Sinapis alba L.) seedling as affected by nitrate, phytochrome and photooxidative damage of plastids (1986)
    Springer
    Planta 168 (1986), S. 369-376 
    Details
    ISSN: 1432-2048
    Keywords: Nitrate assimilation ; Nitrate reductase ; Nitrite reductase ; Phytochrome ; Plastidic signal ; Sinapis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrite reductase (NIR; EC 1.7.7.1) is a central enzyme in nitrate assimilation and is localized in plastids. The present study concerns the regulation of the appearance of NIR in cotyledons of the mustard (Sinapis alba L.) seedling. It was shown that light exerts its positive control over the nitrate-mediated induction of NIR via the farred-absorbing form of phytochrome. Without nitrate the light effect cannot express itself; even though the light signal is accumulated in the cotyledons it remains totally cryptic in the absence of nitrate. Moreover, it was recognised that ‘intact plastids’ are important in the control of the appearance of NIR. If the plastids are damaged by photooxidation the action of nitrate and phytochrome on NIR appearance is abolished. The appearance of nitrate reductase (NR; EC 1.6.6.1) responds similarly to photooxidative damage even though this enzyme is cytosolic. While the data strongly indicate that some ‘plastidic signal’ is a prerequisite for the nitrate-induced and phytochrome-modulated appearance of NIR and NR, the possibility could not be ruled out that photooxidative damage affects the accumulation of NIR in the organelle.
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    URL: http://dx.doi.org/10.1007/BF00392362
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    Regulatory factors involved in gene expression (subunits of ribulose-1,5-bisphosphate carboxylase) in mustard (Sinapis alba L.) cotyledons (1986)
    Springer
    Planta 169 (1986), S. 260-266 
    Details
    ISSN: 1432-2048
    Keywords: Gene expression ; Phytochrome ; Plastidic factor ; Ribulose-1,5-bisphosphate carboxylase ; Sinapis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phytochrome-controlled appearance of ribulose-1,5-bisphosphate carboxylase (RuBP-Case) and its subunits (large subunit LSU, small subunit SSU) was studied in the cotyledons of the mustard (Sinapis alba L.) seedling. The main results were as follows: (i) Control of RuBPCase appearance by phytochrome is a modulation of a process which is turned on by an endogenous factor between 30 and 33 h after sowing (25° C). Only 12 h later the process begins to respond to phytochrome. (ii) The rise in the level of RuBP-Case is the consequence of a strictly coordinated synthesis de novo of the subunits. (iii) While the levels of translatable mRNA for SSU are compatible with the rate of SSU synthesis the relatively high LSU mRNA levels are not reflected in the rates of in-vivo LSU or RuBPCase syntheses. (iv) Gene expression is also abolished in the case of nuclear-encoded SSU if intraplastidic translation and concomitant plastidogenesis is inhibited by chloramphenicol, pointing to a “plastidic factor” as an indispensable prerequisite for expression of the SSU gene(s). (v) Regarding the control mechanism for SSU gene expression, three factors seem to be involved: an endogenous factor which turns on gene expression, phytochrome which modulates gene expression, and the plastidic factor which is an indispensable prerequisite for the appearance of translatable SSU mRNA.
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    Fluence dependence of the ultraviolet-light-induced accumulation of chalcone synthase mRNA and effects of blue and far-red light in cultured parsley cells (1986)
    Springer
    Planta 169 (1986), S. 393-398 
    Details
    ISSN: 1432-2048
    Keywords: Chalcone synthase ; Fluence-response relation ; Petroselinum ; Phytochrome ; Receptor UV-B blue-light
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The fluence dependence of the time course of accumulation of chalcone synthase mRNA in ultraviolet (UV)-light-irradiated cell suspension cultures of parsley (Petroselinum crispum) and the additional effects of blue and far-red light have been investigated. Variations of the UV fluence had no detectable influence on the initial rate of increase in mRNA amount or translational activity, nor on the preceding lag period of approximately 3 h, but strongly influenced the duration of the transient increase. The effects were the same whether the fluence rate or the time of irradiation was varied to obtain a given fluence. Blue-light pretreatment of the cells resulted in increased amounts of mRNA and abolished the apparent lag period. This effect remained cryptic without the subsequent UV-light treatment. Irradiation with long-wavelength far-red light following UV-light pulses shortened the duration of the mRNA accumulation period. This effect was not altered by a preceding blue-light treatment. Thus, three photoreceptors, a UV-B receptor, a blue-light receptor and phytochrome, participate in the regulation of chalcone synthase mRNA accumulation in this system.
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    URL: http://dx.doi.org/10.1007/BF00392136
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    Expression of nuclear genes as affected by treatments acting on the plastids (1986)
    Springer
    Planta 168 (1986), S. 482-492 
    Details
    ISSN: 1432-2048
    Keywords: Nuclear gene expression ; Photooxidation of chloroplast ; Phytochrome ; Sinapis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In a preceding paper (Oelmüller and Mohr 1986, Planta 167, 106–113) it was shown that in the cotyledons of the mustard (Sinapis alba L.) seedling the integrity of the plastid is a necessary prerequisite for phytochrome-controlled appearance of translatable mRNA for the nuclear-encoded small subunit (SSU) of ribulose-1,5-bisphosphate carboxylase and the light-harvesting chlorophyll a/b-binding protein of photosystem II (LHCP). It was concluded that a signal from the plastid is essential for the expression of nuclear genes involved in plastidogenesis. The present study was undertaken to characterize this postulated signal. Chloramphenicol, an inhibitor of intraplastidic protein synthesis and Norflurazon, an inhibitor of carotenoid synthesis (to bring about photooxidative sensitivity of the plastids) were applied. We obtained the following major results. (i) After a brief period of photooxidative damage a rapid decrease of the above translatable mRNAs was observed. Conclusion: the signal is short-lived and thus required continually. (ii) Once the plastids became damaged by photooxidation, no recovery with regard to nuclear gene expression was observed after a transfer to non-damaging light conditions. Conclusion: even a brief period of damage suffices to prevent production of the signal. (iii) Chloramphenicol inhibited nuclear gene expression (SSU, LHCP) and plastidic development when applied during the early stages of plastidogenesis. Once a certain stage had been reached (between 36–48 h after sowing at 25° C) nuclear gene expression became remarkably insensitive toward inhibition of intraplastidic translation. Conclusion: a certain developmental stage of the plastid must be reached before the signal is released by the plastid. (iv) Under the growth conditions we adopted in our experiments the plastids in the mesophyll cells of mustard cotyledons developed essentially between 36 and 120 (-144) h after sowing. Only during this period could translatable mRNAs for SSU and LHCP be detected. Conclusion: the signal is released by the plastids only during this time span.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392267
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  • 94
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    Effect of ammonium and nitrate on growth and appearance of nitrate reductase and nitrite reductase in dark- and light-grown mustard seedlings (1986)
    Springer
    Planta 169 (1986), S. 594-599 
    Details
    ISSN: 1432-2048
    Keywords: NH 4 + -toxicity ; Nitrate assimilation ; Nitrate reductase ; Nitrite reductase ; Phytochrome ; Sinapis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrate-induced and phytochrome-modulated appearance of nitrate reductase (NR; EC 1.6.6.1) and nitrite reductase (NIR; EC 1.7.7.1) in the cotyledons of the mustard (Sinapis alba L.) seedling is strongly affected by externally supplied ammonium (NH 4 + ). In short-term experiments between 60 and 78 h after sowing it was found that in darkness NH 4 + —simultaneously given with NO 3 - —strongly inhibits appearance of nitrate-inducible NR and NIR whereas in continuous far-red light—which operates exclusively via phytochrome without significant chlorophyll formation —NH 4 + (simultaneously given with NO 3 - ) strongly stimulates appearance of NR. The NIR levels are not affected. This indicates that NR and NIR levels are regulated differently. In the absence of external NO 3 - appearance of NR is induced by NH4 in darkness as well as in continuous far-red light whereas NIR levels are not affected. On the other hand, in the absence of external NO 3 - , exogenous NH 4 + strongly inhibits growth of the mustard seedling in darkness as well as in continuous far-red light. This effect can be abolished by simultaneously supplying NO 3 - . The adverse effect of NH 4 + on growth (‘NH 4 + -toxicity’) cannot be attributed to pH-changes in the medium since it was shown that neither the growth responses nor the changes of the enzyme levels are related to pH changes in the medium. Non-specific osmotic effects are not involved either.
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    URL: http://dx.doi.org/10.1007/BF00392112
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  • 95
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    Effects of red and far red lights on nodulation and nitrogen fixation in soybean (Glycine max L.Merr) (1986)
    Springer
    Plant and soil 92 (1986), S. 427-430 
    Details
    ISSN: 1573-5036
    Keywords: Light ; Nitrogen ; Fixation ; Nodulation ; Phytochrome ; Soybean
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Rooted leaves and plants were irradiated at the end of the photoperiod with red light for 15 minutes, while another group was also irradiated with red light and immediately afterwards with far- red light. The reduction in Pfr/Ptotal established by far red irradiation promoted nodulation probably by affecting an hormonal balance.
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    URL: http://dx.doi.org/10.1007/BF02372490
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  • 96
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    Effects of light on the cell cycle in the shoot apex ofSilene coeli-rosa L. on the first day of floral induction (1985)
    Springer
    Protoplasma 124 (1985), S. 96-105 
    Details
    ISSN: 1615-6102
    Keywords: Cell cycle ; DNA ; Phytochrome ; shoot apex ; Silene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 28-day-old plants ofSilene coeli-rosa were exposed, at 1,700 hours, to 5 minutes far-red light, 5 minutes red, 5 minutes far-red followed by 5 minutes red light, or maintained in darkness (short day controls). All plants were exposed to tritiated (methyl-3H-)thymidine for 2 hours (1645–1845) and subsequently sampled at 2-hour intervals for 24 hours. The length of the cell cycle (pulse-label mitoses (PLM) method) and changes in cell number were measured in the shoot apical meristems. The cell cycle in the short day controls was 16–17 hours compared with a mean cell generation time of 18 hours. Exposing plants to far-red light resulted in a shortening of the cell cycle to 11 hours, red light resulted in a shortened cycle of 12 hours whilst far-red, red gave a value of 9 hours. Mean cell generation times following each light treatment were approximetely 2–5 hours longer than the corresponding cell cycle times, suggesting that the shortened cell cycles reverted to longer cycles over the experimental period. Measurements of the proportions of cells with the 2C and 4C amounts of DNA in the apical meristems of unlabeled plants indicated that G1 shortened but G2 lengthened in response to far-red light. A measurement of the labeling index also indicated that S-phase shortened in response to far-red. These data also suggested that red light caused G1 to shorten and G2 to lengthen although the corresponding PLM curve was consistent with a dramatic shortening of G2. Far-red followed by red resulted in decreases in the durations of both G2 and G1.
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    URL: http://dx.doi.org/10.1007/BF01279728
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  • 97
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    Zum Einfluß externer Punktladungen auf das Absorptionsspektrum von Gallenfarbstoffen des Bilatrien-abc-typs (1984)
    Springer
    Monatshefte für Chemie 115 (1984), S. 121-124 
    Details
    ISSN: 1434-4475
    Keywords: Bilatriene-abc ; Biliverdin ; Phytochrome ; Spectrophotometric titration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Spectrophotometric titrations of biliverdin (1) and a bilatriene-abc bearing an amine substituted chain (3) revealed an external charge induced bathochromic shift of the absorption spectrum in case of the positive non conjugated charge (3). This shift is in the order of 30 nanometers.
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    URL: http://dx.doi.org/10.1007/BF00798429
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  • 98
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    Identification of calmodulin in the green alga Mougeotia and its possible function in chloroplast reorientational movement (1984)
    Springer
    Planta 162 (1984), S. 62-67 
    Details
    ISSN: 1432-2048
    Keywords: Calcium (chloroplast movement) ; Calmodulin (chloroplast movement) ; Chloroplast movement (Mougeotia) ; Mougeotia ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A soluble protein was isolated from Mougeotia by chloropromazine-sepharose 4 B affinity chromatography. The protein matches the properties of calmodulin in terms of heat stability, Ca2+-dependent electrophoretic mobility in sodium-dodecyl-sulfate polyacrylamide gels, and its ability to activate cyclic nucleotide phosphodiesterase in a Ca2+-dependent manner. Phytochrome-mediated chloroplast reorientational movement in Mougeotia was inhibited by the calmodulin antagonist trifluoperazine, a hydrophobic compound, or N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7), a hydrophilic compound; 50% inhibition (IC50) of chloroplast movement is caused by 20–50 μmol l-1 trifluoperazine or 100 μmol l-1 W-7. The Ca2+-calmodulin may act as an intermediate in the chloroplast reorientational response in Mougeotia governed by phytochrome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397422
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  • 99
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    Effect of light and temperature on the germination of lettuce seeds (1984)
    Springer
    Planta 160 (1984), S. 190-192 
    Details
    ISSN: 1432-2048
    Keywords: Lactuca ; Phytochrome ; Seed germination ; Temperature and seed germination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A short period (15–30 min) at 30° C promotes germination of seeds of Lactuca sativa L. cv. Repolhuda in darkness. Far-red light reverses this stimulation, and the escape curves for phytochrome and high-temperature action are quite similar, indicating that the two factors act at a common point in the chain of events leading to germination. It is suggested that high temperature acts by decreasing the threshold of the active, far-red absorbing, form of phytochrome (Pfr) needed to promote germination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392870
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  • 100
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    Coaction of light and cytokinin in photomorphogenesis (1983)
    Springer
    Planta 159 (1983), S. 136-142 
    Details
    ISSN: 1432-2048
    Keywords: Anthocyanin ; Carotenoid ; Coaction analysis ; Cotyledon growth ; Glyceraldehyde-3-phosphate dehydrogenase ; Phytochrome ; Sinapis ; Zeatin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Intact mustard seedlings were treated with zeatin and photomorphogenetically active light in different ways: (1) hormone treatment preceding light treatment, (2) light treatment preceding hormone treatment, (3) hormone and light applied simultaneously. Under all experimental conditions the effect of the hormone treatment is multiplicative to the light effect with regard to the increase of cotyledon area. However, the hormone effect is additive to the light effect with regard to increases of the level of NADPH-dependent glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.13) and carotenoid contents. Anthocyanin synthesis is inhibited by exogenous zeatin whereby the concentration response curves are similar, irrespective of the extent of anthocyanin formation mediated by light. However, an interaction was found in the sense that the responsiveness toward zeatin is decreased somewhat by the action of phytochrome. Our results show that the responsiveness to light (via the far-red-absorbing form of phytochrome; P fr) is not changed by a preceding or simultaneous hormone treatment. Moreover, the responsiveness of the plant to exogenously applied zeatin is not affected — except in anthocyanin synthesis — by a preceding or simultaneous light treatment. We conclude from our results that the action of phytochrome on the developmental processes is not related to cytokinin levels.
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    URL: http://dx.doi.org/10.1007/BF00392984
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