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  • 1
    Electronic Resource
    Electronic Resource
    Identification and quantification of three active auxins in different tissues of Tropaeolum majus (2002)
    Oxford, UK : Blackwell Science, Ltd
    Physiologia plantarum 115 (2002), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Indole-3-acetic acid (IAA), indole-3-butyric acid (IBA) and phenylacetic acid (PAA) were identified as endogenous compounds with auxin activity in nasturtium (Tropaeolum majus L.) by full scan gas chromatography-mass spectrometry. The endogenous concentrations of the three auxins were measured by GC-selected ion monitoring-MS and isotope dilution analysis using stable labelled isotopes. PAA was present at concentrations about 10- to 100-fold lower than IAA, whereas IBA was found to be in the same concentration range as IAA. Free IAA was highest in roots followed by young leaves. IBA was also highest in the roots, and relatively high concentrations were found in young leaves and flowers. The distribution of PAA was quite different from that found for IBA. No PAA could be detected in young leaves and flowers, and in all other tissues studied the concentrations were well below those of the other two auxin compounds. The presence of a nitrilase gene family and nitrilase activity in extracts from T. majus suggests that PAA might be synthesized by the nitrilase pathway using benzylglucosinolate as precursor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2002.1150220.x
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  • 2
    Electronic Resource
    Electronic Resource
    Red-light-regulated growth (1998)
    Springer
    Planta 204 (1998), S. 207-211 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Auxin ; Growth ; Epidermis ; Indole-3-acetic acid ; Red light ; Zea (mesocotyl)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The etiolated maize (Zea mays L.) shoot has served as a model system to study red light (R)-regulated growth. Previous studies have shown that R inhibition of maize mesocotyl elongation involves a change in the auxin economy. Shown here is that R causes an increased tension in the epidermis relative to the inner tissue indicating that the growth of the epidermis is preferentially inhibited by R irradiation. This observation, taken together with previous indirect estimates of auxin within the epidermis, has prompted the hypothesis that R mediates the inhibition of mesocotyl elongation by preferentially decreasing auxin in the epidermis, a tissue which constrains the growth of the organ. We tested this hypothesis using gas chromatography-selected ion monitoring-mass spectrometry analysis of free indole-3-acetic acid (IAA) levels in both the apical 1 cm of the mesocotyl and the corresponding epidermis of etiolated and 4-h, R-irradiated seedlings. Red light irradiation caused a 1.4-fold reduction in free IAA within the whole section of the apical mesocotyl. However, within the peeled mesocotyl epidermis, R irradiation caused at least a 1.9-fold reduction in free IAA. To determine if the nearly twofold decrease in epidermal auxin occurring after R is physiologically significant, IAA was differentially applied to opposite sides of shoots. A twofold difference in IAA application rate caused asymmetrical growth. Thus, the twofold R-induced decrease in free IAA level in the epidermis, a difference sufficient to affect growth, and the rapid R-induced change in growth rate in the epidermis are consistent with the hypothesis that R causes growth of the mesocotyl to decrease by preferentially regulating the free IAA level in the mesocotyl epidermis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050248
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  • 3
    Electronic Resource
    Electronic Resource
    Indole glucosinolate and auxin biosynthesis in Arabidopsis thaliana (L.) Heynh. glucosinolate mutants and the development of clubroot disease (1999)
    Springer
    Planta 208 (1999), S. 409-419 
    Details
    ISSN: 1432-2048
    Keywords: Key words:Arabidopsis ; Auxin ; Clubroot disease ; Glucosinolate ; Plasmodiophora
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Mutants and wild type plants of Arabidopsis thaliana were analysed for differences in glucosinolate accumulation patterns, indole-3-acetic acid (IAA) biosynthesis and phenotype. A previously identified series of mutants, termed TU, with altered glucosinolate patterns was used in this study. Only the line TU8 was affected in shoot phenotype (shorter stems, altered branching pattern). Synthesis of IAA and metabolism were not much affected in the TU8 mutant during seedling development, although the content of free IAA peaked earlier in TU8 during plant development than in the wild type. Indole glucosinolates and IAA may, however, be involved in the development of clubroot disease caused by the obligate biotrophic fungus Plasmodiophora brassicae since the TU3 line had a lower infection rate than the wild type, and lines TU3 and TU8 showed decreased symptom development. The decline in clubroot formation was accompanied by a reduced number of fungal structures within the root cortex and slower development of the fungus. Indole glucosinolates were lower in infected roots of TU3 and TU8 than in control roots of these lines, whereas in wild-type plants the differences were not as prominent. Free IAA and indole-3-acetonitrile (IAN) were increased in infected roots of the wild type and mutants with normal clubroot symptoms, whereas they were reduced in infected roots of mutants TU3 and TU8. These results indicate a role for indole glucosinolates and IAN/IAA in relation to symptom development in clubroot disease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050576
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  • 4
    Electronic Resource
    Electronic Resource
    A microtechnique for the analysis of free and conjugated indole-3-acetic acid in milligram amounts of plant tissue using a benchtop gas chromatograph-mass spectrometer (1997)
    Springer
    Planta 204 (1997), S. 1-7 
    Details
    ISSN: 1432-2048
    Keywords: Key words:Arabidopsis (auxin analysis) ; Auxin analysis ; Avena (auxin analysis) ; Mass spectrometry ; Stable isotopes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. A microtechnique was developed for the quantification of indole-3-acetic acid (IAA) in plant samples of one milligram fresh weight or less. The method permitted quantification of both free and conjugated IAA using a benchtop gas chromatograph-mass spectrometer. New methods for sample purification with high recovery at microscale levels, together with simple changes that result in enhanced sensitivity of the instrumentation, allowed for a significant reduction in the amount of plant material required for analysis. Single oat (Avena sativa L.) coleoptile tips could be studied with this method and were found to contain free and total IAA levels of 137 and 399 pg · mg−1 fresh weight, respectively. A single 5-d-old Arabidopsis thaliana (L.) Heynh. seedling was shown to contain 61 pg · mg−1 fresh weight free IAA and 7850 pg · mg−1 fresh weight of total IAA following basic hydrolysis. This microtechnique provides a way to accurately measure IAA levels in very small structures and individual seedlings, thus making it a valuable research tool for elucidating the role and distribution of auxin in relation to growth and development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050223
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  • 5
    Electronic Resource
    Electronic Resource
    The bound auxins: Protection of indole-3-acetic acid from peroxidase-catalyzed oxidation (1978)
    Springer
    Planta 139 (1978), S. 203-208 
    Details
    ISSN: 1432-2048
    Keywords: Auxin (bound) ; Auxin oxidation ; IAA oxidase ; Peroxidase ; Pisum ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Indole-3-acetic acid (IAA) was oxidized by horseradish peroxidase, but ester and amide conjugates of IAA were not degraded. Addition of indoleacetyl-myo-inositol, indoleacetyl-L-aspartate, indoleacetylglycine, indoleacetyl-L-alanine, indoleacetyl-D-alanine, or indoleacetyl-β-alanine did not affect the rate of oxidation of IAA by horseradish peroxidase. Peroxidase preparations from Pisum sativum L. and Zea mays L. behaved similarly in that they rapidly oxidized IAA, but not conjugates found in the plant from which the peroxidase was prepared. These results indicate that conjugation could affect the stability of IAA in vivo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00388631
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  • 6
    Electronic Resource
    Electronic Resource
    Uptake and metabolism of benzyladenine during shoot organogenesis in Petunia leaf explants (1992)
    Springer
    Plant growth regulation 11 (1992), S. 105-114 
    Details
    ISSN: 1573-5087
    Keywords: Cytokinin ; benzyladenine ; metabolism ; shoot organogenesis ; Petunia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Benzyladenine (BAP) uptake and metabolism were characterized during the key stages of shoot organogenesis in leaf explants of Petunia ‘MD1’. Using leaf explant transfer experiments, it was shown that exposure to 2.2 μM BAP for 6, 8 or 10 days induced shoot formation on 27, 80 and 100% of the explants respectively, with a concomitant increase in the number of shoots per explant. BAP uptake and metabolism were characterized in leaf explants after 1, 3, 6 or 10 days exposure to [3H]BAP or 10 days exposure plus an additional 2 days on basal medium (10+2). BAP and 9-β-D-ribofuranosyl-BAP ([9R]BAP) were detected at days 1 and 3 only. Therefore, the BAP free base was not detectable during the shoot induction period between days 6 and 10, as defined by leaf transfer experiments. The BAP ribotide pool was largest on day 1 and decreased to day 10+2. It is possible that the BAP ribotide pool provided either the active cytokinin itself or acted as a short-term storage form for the active cytokinin in petunia shoot organogenesis. Other metabolites detected in petunia leaf tissue included 7-β-D-glucopyranosyl-BAP ([7G]BAP), 9-β-D-glucopyranosyl-BAP ([9G]BAP) and an unidentified metabolite C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00024063
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  • 7
    Electronic Resource
    Electronic Resource
    Differential inhibition of indole-3-acetic acid and tryptophan biosynthesis by indole analogues. I. Tryptophan dependent IAA biosynthesis (1999)
    Springer
    Plant growth regulation 27 (1999), S. 57-62 
    Details
    ISSN: 1573-5087
    Keywords: auxin biosynthesis ; auxin inhibitors ; indole analogues ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Maize liquid endosperm extracts contain the enzymes necessary for all of the steps of the plant IAA biosynthetic pathway from tryptophan, and provide a means to assay the pathway in vitro. We have analyzed the reactions in the presence of a series of indole and indole-like analogues in order to evaluate the potential of these compounds to act as inhibitors of IAA biosynthesis. Such inhibitors will be useful to investigate the tryptophan to IAA pathway, to determine the precursors and intermediates involved, and to select for mutants in this process. A number of such compounds were tested using in vitro enzyme assays for both the tryptophan dependent IAA biosynthesis pathway and for tryptophan synthase β activity. Some compounds showed strong inhibition of IAA biosynthesis while having only a slight effect on the reaction rate of tryptophan synthase β. These results: (1) show that IAA biosynthesis can be selectively inhibited relative to tryptophan biosynthesis; (2) suggest potential ways to screen for IAA biosynthetic pathway mutations in plants; and (3) provide additional tools for studies of IAA biosynthesis in plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006103902155
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  • 8
    Electronic Resource
    Electronic Resource
    Identification of indole-3-butyric acid as an endogenous constituent of maize kernels and leaves (1989)
    Springer
    Plant growth regulation 8 (1989), S. 215-223 
    Details
    ISSN: 1573-5087
    Keywords: IAA ; IBA ; conjugated IBA ; rooting ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Indole-3-butyric acid (IBA) was identified by thin layer chromatography, gas-liquid chromatography and gas chromatography-mass spectrometry in kernels and leaves of corn (Zea mays) var. Hazera 224. Free and ester conjugated IBA were present in dry and germinating corn kernels and leaves. This is the first report of IBA in a monocotyledonous plant and, as far as we know, the first evidence for the presence of conjugated IBA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00025391
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  • 9
    Electronic Resource
    Electronic Resource
    Indole-3-acetic acid biosynthesis in Lemna gibba studied using stable isotope labeled anthranilate and tryptophan (1999)
    Springer
    Plant growth regulation 27 (1999), S. 139-144 
    Details
    ISSN: 1573-5087
    Keywords: auxin ; duckweed ; indolic metabolism ; metabolic compartmention ; stable isotopes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract IAA biosynthesis in many plants, including Lemna gibba, has been shown to involve at least two different pathways, one from tryptophan and a tryptophan-independent route. To study the kinetics of IAA biosynthesis in Lemna, we simultaneously measured the incorporation of label from [15N]-anthranilate and [2H5]-tryptophan into IAA by Lemna plants in short term feeding studies. The data show that label from anthranilate rapidly goes into IAA and tryptophan. Labeling of the IAA pool by [15N]-anthranilate slightly precedes labeling of the tryptophan pool, confirming that more than one route to IAA exists in these plants. Longer term feeding studies (5–25 h) suggest that exogenous tryptophan is used preferentially to label IAA as compared to tryptophan made by the plant. This is indicated by the fact that the IAA pool was more enriched than the tryptophan pool in [2H5]-label, but less enriched than the tryptophan pool in [15N] (which comes about by de novo synthesis of tryptophan from [15N]-anthranilate by the plant).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006191502391
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  • 10
    Electronic Resource
    Electronic Resource
    Structural characterization and auxin properties of dichlorinated indole-3-acetic acids (1999)
    Springer
    Plant growth regulation 27 (1999), S. 21-31 
    Details
    ISSN: 1573-5087
    Keywords: auxin ; Avena sativa straight growth test ; biological activity ; dichlorinated indole-3-acetic acid ; structural characterization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The dichlorinated indole-3-acetic acids: 4,5-Cl2-IAA, 4,6-Cl2-IAA, 4,7-Cl2-IAA, 5,6-Cl2-IAA, 5,7-Cl2-IAA and 6,7-Cl2-IAA were synthesized and characterized by X-ray structure analysis to unambiguously identify the substances for bioassays required to establish structure activity relationships of auxins and their analogues. Straight-growth tests were performed on Avena sativa coleoptiles to correlate their auxin activity with molecular properties which could reveal information on the topology of the auxin binding site. Structure/activity correlations revealed that the 5,6-Cl2-IAA molecule, by virtue of its size and shape, fits particularly well into the active site cavity of the receptor protein. The main contact of the substrate or inhibitor in the receptor active site via the carboxylic group determines their orientation in the active site cavity. As a consequence, the 5,6-substituted sites protrude into the widest part of the active site whereas the 7-, 4-, and 5-substituted sites are oriented towards the narrowest part of the active site. These topological parameters are in agreement with the high auxin activity of 5,6-Cl2-IAA and the low activity of 4,7-Cl2-IAA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006031527789
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