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  • photosynthesis  (93)
  • gene expression  (83)
  • Springer  (176)
  • American Meteorological Society
  • Institute of Physics
  • 1995-1999  (87)
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  • Springer  (176)
  • American Meteorological Society
  • Institute of Physics
  • Wiley-Blackwell  (14)
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  • 1995-1999  (87)
  • 1990-1994  (89)
  • 1940-1944
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  • 1
    Electronic Resource
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    Springer
    Entomologia experimentalis et applicata 63 (1992), S. 101-102 
    ISSN: 1570-7458
    Keywords: Cnaphalocrosis medinalis ; rice leaffolder ; Oryza sativa ; rice ; photosynthesis ; transpiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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  • 2
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    BioMetals 11 (1998), S. 345-358 
    ISSN: 1572-8773
    Keywords: calcium ; CREB ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Through the evolution of multicellular organisms, calcium has emerged as the preferred ion for intracel-lular signalling. It now occupies a pivotal role in many cell types and nowhere is it more important than in neurons, where it mediates both the relaying and long-term storage of information. The latter is a process that enables learning and memory to be formed and requires the activation of gene expression by calcium signals. Evidence from a number of diverse organisms shows that transcription mediated by the transcrip-tion factor CREB is critical for learning and memory. Here we review the features of CREB activation by calcium signals in mammalian cells. In contrast to other transcription factors, its regulation is dependent on an elevation of nuclear calcium concentration, potentially placing this spatially distinct pool of calcium as an important mediator of information storage.© Kluwer Academic Publishers
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  • 3
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    BioMetals 5 (1992), S. 149-156 
    ISSN: 1572-8773
    Keywords: Hg2+ toxicity ; cyanobacterium ; Nostoc calcicola ; growth ; photopigments ; nucleic acids ; photosynthesis ; membrane integrity ; nutrient uptake ; enzymes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Toxicological responses of the filamentous N2-fixing cyanobacteriumNostoc calcicola Bréb. towards Hg2+ were studied to enumerate the decisive lethal events. In low-dose, long-term experiments (0.05–0.25 μm Hg2+, 10 days), photoautotrophic growth was severely inhibited with concurrent loss of photosynthetic pigments (phycocyanin〉chlorophyll α〉carotenoids) and nucleic acids. The termination of growth after a day 4 exposure to 0.25 μm Hg2+ has been attributed to the complete inhibition ofin vivo photosynthetic activity in the cyanobacterium (O2 evolution〉14CO2 incorporation). The elevated Hg2+ concentrations irreversibly damaged the cell membrance as observed under light microscopy, and as indicated by the leakage of intracellular electrolytes and phycocyanin. In high-dose, short-term experiments (0.5–20.0 μm Hg2+, up to 6 h), thein vivo activities of selected enzymes (glutamine synthetase 〉 nitrate reductase 〉 nitrogenase) were less inhibited by Hg2+ than the uptake of nutrient ions (NH 4 + 〉NO 3 − 〉PO 4 3− ).
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  • 4
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    Plant molecular biology reporter 16 (1998), S. 323-339 
    ISSN: 1572-9818
    Keywords: Aux/IAA genes ; gene expression ; gene families ; RT-PCR ; tomato
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have developed an improved method for determination of gene expression levels with RT-PCR. The procedure is rapid and does not require extensive optimization or densitometric analysis. Since the detection of individual transcripts is PCR-based, small amounts of tissue samples are sufficient for the analysis of expression patterns in large gene families. Using this method, we were able to rapidly screen nine members of the Aux/IAA family of auxin- responsive genes and identify those genes which vary in message abundance in a tissue- and light-specific manner. While not offering the accuracy of conventional semi-quantitative or competitive RT-PCR, our method allows quick screening of large numbers of genes in a wide range of RNA samples with just a thermal cycler and standard gel analysis equipment.
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  • 5
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    Antonie van Leeuwenhoek 62 (1992), S. 131-153 
    ISSN: 1572-9699
    Keywords: mitochondrial DNA ; mutational analysis ; nucleo-mitochondrial interactions ; gene expression ; membrane assembly ; respiratory deficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In contrast to most other organisms, the yeastSaccharomyces cerevisiae can survive without functional mitochondria. This ability has been exploited in genetic approaches to the study of mitochondrial biogenesis. In the last two decades, mitochondrial genetics have made major contributions to the identification of genes on the mitochondrial genome, the mapping of these genes and the establishment of structure-function relationships in the products they encode. In parallel, more than 200 complementation groups, corresponding to as many nuclear genes necessary for mitochondrial function or biogenesis have been described. Many of the latter are required for post-transcriptional events in mitochondrial gene expression, including the processing of mitochondrial pre-RNAs, the translation of mitochondrial mRNAs, or the assembly of mitochondrial translation products into the membrane. The aim of this review is to describe the genetic approaches used to unravel the intricacies of mitochondrial biogenesis and to summarize recent insights gained from their application.
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  • 6
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    Mangroves and salt marshes 2 (1998), S. 99-107 
    ISSN: 1572-977X
    Keywords: conductance ; mangrove ; photosynthesis ; productivity ; water potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Diurnal gas exchange characteristics were measured simultaneously in two mangrove species, Avicennia marina and Bruguiera gymnorrhiza, over 7 d in summer (February–March), to compare their productivity. The study was undertaken in the Beachwood Mangroves Nature Reserve, Durban, South Africa, using fully expanded leaves of young and mature trees at the top of the canopy. Gas exchange was strongly influenced by photosynthetic photon flux density (PPFD), leaf temperature and the accompanying leaf to air vapour pressure deficit (Δ w). Carbon dioxide exchange was saturated at a PPFD of about 600 μmol m-2s-1 in B. gymnorrhiza compared to 800 μmol m-2s-1 in A. marina. Maximal CO2 exchange occurred between 12h00 and 14h00 and was consistently greater in A. marina (8.8 μmol m-2s-1) than in B. gymnorrhiza (5.3 mu;mol m-2s-1). Mean internal CO2 concentrations ( ci) were 260 μl l-1 in A. marina and 252 μl l-1 in B. gymnorrhiza. Photorespiratory activity was 32% in A. marina and 30% in B. gymnorrhiza. Mean water use efficiency (WUE) was 8.0 μmol mmol-1 in A. marina and 10.6 μmol mmol-1 in B. gymnorrhiza. Diurnal leaf water potentials ranged from –0.8 to –3.5 MPa and were generally lower in A. marina.
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  • 7
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    Mangroves and salt marshes 2 (1998), S. 191-198 
    ISSN: 1572-977X
    Keywords: canopy ; Hinchinbrook ; leaf area index ; mangrove ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Data on stand structure and rates of photosynthesis were used to estimate net canopy carbon fixation and carbon accumulation as living biomass in mangrove forests in Hinchinbrook Channel, Australia. Total annual canopy net carbon fixation was estimated to be about 29 t C ha−1 yr−1. This equates to about 204,000 t C yr−1 for all mangrove forests in Hinchinbrook Channel. Of this, only about 12% was stored as living plant biomass. Although it is not yet possible to present a robust carbon balance for mangrove trees, the remainder is presumably lost through plant respiration, litter fall, root turnover and exudation of organic compounds from roots.
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  • 8
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    Aquatic sciences 54 (1992), S. 321-330 
    ISSN: 1420-9055
    Keywords: Algal pigments ; algal communities ; photosynthesis ; Lake Lugano (Lago di Lugano)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A one-year study of phytoplankton, primary production and related physical and chemical factors was made in a Swiss basin of Lake Lugano (Lago di Lugano). The chlorophylls and 12 carotenoids were analyzed with a TLC technique. The carotenoid monitoring was considered to be particularly interesting, because the role of these pigments in freshwater algae is still very poorly documented by field studies. The dependence of photosynthesis on several factors was statistically evaluated. Evidence was found of light-adaptation phenomena. The variations of photosynthetic activity and efficiency largely depended on the light regime in the few days before the field observations and on the cellular content of chlorophylls and single carotenoids, whose concentrations in their turn were closely linked with light, temperature, average cell size, and with the actual species assemblage.
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  • 9
    ISSN: 1440-1703
    Keywords: Clethra barbinervis ; interspecific difference ; intraspecific variation ; photosynthesis ; SO2 resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of SO2 on the photosynthesis ofClethra barbinervis collected from a smoke-polluted area near the Ashio copper smelter in Tochigi Prefecture was compared withC. barbinervis collected from a nonpolluted district in Tsukuba, Ibaraki Prefecture andQuercus mongolica var.grosseserrata grown in a nonpolluted field in Nagano Prefecture. The plants were exposed to 0.5–1.5 p.p.m. SO2 for 90 min (short-term) and to 0.3 p.p.m. SO2 for 31–39 days (long-term). TheClethra plants from both sites had a lower intrinsic stomatal conductance and photosynthetic rate thanQuercus plants. Short-and long-term fumigation caused stomatal closure inQuercus plants, but had little effect on the stomatal conductance ofClethra plants. Under short-term fumigation, nonstomatal photosynthetic inhibition per unit of absorbed SO2 was smallest inClethra plants from Ashio. Long-term fumigation caused photosynthetic decline and visible foliar injury toQuercus plants, but had no effect onClethra plants from Ashio. Consequently,Clethra plants from Ashio had a higher photosynthetic rate thanQuercus plants after long-term fumigation. These results suggest thatC. barbinervis populations in the smoke-polluted area of Ashio had evolved high SO2 resistance connected with SO2 detoxification ability in mesophyll cells.
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  • 10
    ISSN: 1573-4919
    Keywords: regucalcin ; calcium-binding protein ; gene expression ; calmodulin ; spontaneous hypertensive rats ; rat kidney cortex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The expression of calcium-binding protein regucalcin mRNA in the kidney cortex of rats ingested with saline was investigated. The alteration in regucalcin mRNA levels was analyzed by Northern blotting using liver regucalcin complementary DNA (0.9 kb of open reading frame). Rats were freely given saline as drinking water for 7 days. Regucalcin mRNA levels in the kidney cortex were suppressed by saline ingestion. When calcium chloride (10 mg Ca/100 g body weight) was intraperitoneally administered to rats ingested with saline for 7 days, the effect of calcium administration to increase regucalcin mRNA levels was weakened by saline ingestion. Such effect was also seen by the administration of 2.5 and 5 mg Ca/100 g. Regucalcin mRNA levels in the kidney cortex of spontaneous hypertensive rats (SHR) were not appreciably increased by the administration of calcium (10 mg/100 g). Meanwhile, calcium content in the kidney cortex was significantly elevated by the administration of calcium (10 mg/100 g) to normal rats. This increase was weakened in saline-ingested rats. Moreover, Ca2+/calmodulin-dependent protein kinase activity in the cytosol of kidney cortex was significantly decreased by saline ingestion. These results suggest the possibility that saline ingestion-induced suppression of regucalcin mRNA expression in the kidney cortex is partly involved in the attenuation of Ca2+ signalling.
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  • 11
    ISSN: 1573-4919
    Keywords: mouse ; protein tyrosine phosphatase ; cDNA cloning ; nucleotide sequence ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The PTP-2 cDNA encoding an intracellular protein tyrosine phosphatase (PTPase-2) was isolated and sequenced from mouse testis and T-cell cDNA libraries. This PTP-2 cDNA was found to be homologous to human PTP-TC and rat PTP-S, and contained 1,551 nucleotides, including 1,146 nucleotides encoding 382 amino acids as well as 5′ (61 nucleotides) and 3′ (344 nucleotides) non-coding regions. Northern blot analysis indicated that PTP-2 mRNA of 1.9 Kb was most abundant in testis and kidney, although it was also present in spleen, muscle, liver, heart and brain.
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  • 12
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    Molecular and cellular biochemistry 178 (1998), S. 157-162 
    ISSN: 1573-4919
    Keywords: protein tyrosine phosphatases ; gene expression ; degenerate deoxyoligonucleotides ; RT-PCR ; Swiss 3T3 fibroblasts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The aim of this study was to identify protein tyrosine phosphatases (PTPs) expressed in Swiss 3T3 fibroblasts and to examine their expression levels as well as to characterize quantitative aspects of RT-PCR based on degenerate deoxyoligonucleotides. By using an RT-PCR assay based on degenerate deoxyoligonucleotide primers, expression of mRNAs for two cytoplasmic- and six transmembrane-type PTPs in Swiss 3T3 cells was detected. The sequences of two of them are new. Among nine analyzed PTPs expressed to widely varied extends, only three have mRNA levels high enough to be seen on Northern blots with 10 µg of total RNA per lane. The frequencies with which the examined PTPs are represented among the PCR amplification products, correlate stronger with the primer fidelity, defined as the number of mismatches between the primer- and the cDNA target-sequences, rather than with the PTP expression levels. In conclusion, an RT-PCR assay based on degenerate primers can be successfully used to sample the expressed PTPs and to identify new members of this gene family. However, reliable quantification of their mRNA levels can only be achieved using the classical approaches, like Northern, RNase protection assay or non-degenerate quantitative RT-PCR.
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  • 13
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    Molecular and cellular biochemistry 186 (1998), S. 43-51 
    ISSN: 1573-4919
    Keywords: myocardial ischemia ; gene expression ; growth factors ; phospholamban ; calsequestrin heat shock proteins ; preconditioning ; stunning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Brief periods of coronary occlusion render the affected myocardium more tolarant to the otherwise devastating effects of long coronary occlusion. Besides this phenomena, called ischemic preconditioning, short periods of ischemia cause a regional dysfunction, namely myocardial stunning. The molecular mechanisms of both syndromes are not very well understood. We therefore investigated the expression of genes which may be involved in cardioprotection or repair processes.Using our porcine model of ischemia and reperfusion we were able to show an induction of genes coding for transcription factors (proto-oncogenes), for proteins involved in repair processes (heat shock genes), for proteins implicated in the calcium homeostasis (calcium-handling genes) and for growth factors. We could show that the increased mRNA levels are due to an enhanced transcriptional activity and not to a prolonged half-life of the transcripts. The angiogenic growth factor vascular endothelial growth factor (VEGF) represents an exception. It exhibits - in addition to a HIF-motif (Hypoxia Inducible Factor) in its promoter/enhancer - a protein binding region in its 3′ UTR which when occupied renders the mRNA more stable. However to what extent the expression of the distinct genes contributes to the cardioprotective effect of ischemic preconditioning or myocardial stunning can only be presumed. Increased mRNA stability can be confered via adenosine which is produced during ischemia by ATP-breakdown. The demasking of unknown genes - via differential display reverse transcription polymerase chain reaction (DDRT-PCR) - should provide a more comprehensive view of the mechanisms underlying both processes.
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  • 14
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    Molecular and cellular biochemistry 178 (1998), S. 283-287 
    ISSN: 1573-4919
    Keywords: regucalcin ; calcium-binding protein ; gene expression ; fetal development ; rat liver
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The expression of hepatic calcium-binding protein regucalcin mRNA in fetal rats was investigated. The alteration in regucalcin mRNA levels was analyzed by Northern blotting using liver regucalcin cDNA (0.9 kb with complete open reading frame). Hepatic regucalcin mRNA levels were progressively increased with fetal development; the mRNA was clearly expressed at 15 and 21 days of pregnancy but only slightly at the 8 days. Meanwhile, β-actin mRNA levels in the fetal liver were remarkable at 8 and 15 days of pregnancy. The fetal liver regucalcin mRNA levels at 15 days of pregnancy were significantly decreased by overnight-fasting of maternal rats. The oral administration of calcium chloride (50 mg Ca/100 g body weight) to maternal rats at 15 days of pregnancy caused a remarkable elevation (about 2 fold) of regucalcin mRNA levels in the fetal liver; this increase was seen 60 and 180 min after the calcium administration. After birth, regucalcin mRNA was increasingly expressed in the livers of newborn and weanling rats, while hepatic β-actin mRNA expression was not appreciably altered with increasing ages. These findings demonstrate that the expression of hepatic regucalcin mRNA is increased with fetal development, and that the gene expression may be stimulated by the ingestion of dietary calcium.
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  • 15
    ISSN: 1573-4919
    Keywords: extremely low frequency magnetic fields ; gene expression ; neuron derived orphan receptor-1 ; signal transduction ; Chinese hamster ovary K1 cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Enhanced expression of neuron derived orphan receptor (NOR-1) gene was observed by exposure of Chinese hamster ovary K1 (CHO-K1) cells to an extremely low frequency magnetic field (ELFMF) of 50 Hz at 400 mT, but not at 5 mT. The enhanced expression, reaching the maximum at 6 h, was transient and reduced to the control level after exposure to 400 mT ELFMF for 24 h. The NOR-1 expression induced by treatment with forskolin and TPA was further enhanced by the simultaneous treatment with 400 mT ELFMF, in which the maximum response was at 3 h. The NOR-1 expression by these treatments was induced more earlier than that by 400 mT ELFMF alone. When cells were treated with an inhibitor of the protein kinase C (calphostin C or crocetin) and Ca2+ entry blockers (nifedipin and dantrolen) during the 400 mT ELFMF exposure, the enhanced NOR-1 expression was not observed. Exposure of CHO-K1 cells to the high-density 400 mT ELFMF may affect the signal transduction in the cells, resulting in the enhanced NOR-1 gene expression.
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  • 16
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    Molecular and cellular biochemistry 188 (1998), S. 41-48 
    ISSN: 1573-4919
    Keywords: zinc ; transcription factors ; gene expression ; organogenesis ; Xenopus laevis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Zinc regulates the gene expression machinery. It affects the structure of chromatin, the template function of its DNA, the activity of numerous transcription factors and of RNA polymerases. Hence, it determines both the types of mRNA transcripts synthesized and the rate of transcription itself. Alterations in one or more of these zinc dependent processes have been proposed to account for the proliferative arrest and teratology induced by zinc deficiency. To examine this proposal, studies of zinc during X. laevis development have been initiated. The kinetics of X. laevis oocyte zinc uptake and storage and of zinc utilization during embryogenesis have been examined first. Vitellogenin carries zinc into the oocyte. Ten % of the total zinc (10 ng/egg) remains within the cytosol while 90% (90 ng/egg) is stored in the yolk platelets associated with lipovitellin. The cytosolic pool is the source of the zinc for all newly formed metalloproteins involved in embryo development. The yolk platelet zinc pool is stored for later use during early metamorphosis. It is now possible to examine zinc transfer to molecules, such as e.g. transcription factors, and the role of the metal in their function in development and organogenesis.
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  • 17
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    Molecular and cellular biochemistry 189 (1998), S. 107-111 
    ISSN: 1573-4919
    Keywords: gene expression ; electromagnetic fields ; superinduction ; anisomycin ; immediate early gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Rat pheochromocytoma PC12 cells have been treated with nerve growth factor (NGF) at final concentrations of 2, 4, 8, and 16 ng/ml, and then were exposed to 60-Hz, sinusoidal magnetic fields (MF) of 12.5, 25, 50, and 100 μT (rms) for 30 min. Transcript levels for both c-fos and glyceraldehyde-3 -phosphate dehydrogenase were determined by Northern blot analysis using 32P-labeled cDNA probes. No change in c-fos expression was measured at any condition employed. Treatment of PC12 cells with a combination of agents (NGF, forskolin, and tetradecanoylphorbol acetate [TPA]) increased c-fos expression over that detected with NGF alone. MF exposure of cells treated with the three-agent regimen produced two outcomes, either no change or a doubling of c-fos expression. In subsequent experiments, cells were treated with NGF, NGF + forskolin + TPA, or pre-treated with anisomycin and then treated with NGF + forskolin + TPA. It was determined that MF exposure, like superinduction with anisomycin, increased c-fos expression only in cultures which were not yet exhibiting maximal c-fos expression. It is hypothesized that MF exposure, like anisomycin, may alter the activity of key intracellular protein kinases.
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  • 18
    ISSN: 1573-4978
    Keywords: gene expression ; nuclear matrix proteins ; ocular lens epithelial cells ; transcription factors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Association of transcription factors with the nuclear matrix represents a mechanism by which nuclear architecture may influence transcriptional control of gene expression. This investigation examines nuclear matrix associated proteins (NMP's) isolated from ocular lens epithelial cells by monitoring DNA binding activities using consensus oligonucleotides recognized by the transcription factors YY1, AML-1, AP-1, SP-1 and ATF. The nuclear matrix fractions tested included an immortilized human lens epithelial cell line containing the SV40 large T-antigen, and two mouse lens epithelial cell lines derived from either a normal mouse or a cataract mouse. A rabbit epidermal epithelial cell line and HeLa cells were also included in this study for comparison. The data from these experiments reveal that ubiquitously represented and tissue restricted regulatory proteins are associated with nuclear matrix of lens epithelial cells. The functional significance of the nuclear matrix association of these transcription factors remains to be determined. However, our findings raise the possibility that the transcription factors associated with the nuclear matrix could have specific roles in gene regulation and eye tissue development.
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  • 19
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    Molecular biology reports 16 (1992), S. 277-284 
    ISSN: 1573-4978
    Keywords: translational initiation ; 18S rRNA ; mRNA secondary structure ; gene expression ; initiation mutants ; β-galactosidase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To learn if an mRNA·18S rRNA interaction or a special secondary structure in the mRNA start region is essential for translation in eukaryotic cells, we constructed recombinant plasmids with the SV40 early promoter 5′ to part of the Escherichia coli tuf B-lacZ gene. Deletion of bases potentially complementary to the 18S rRNA highly increased the transient β-galactosidase expressed in transfected CHO cells. Deletion of bases that fostered formation of potential hairpins with the mRNA 5′-terminus or altered the structure of the coding region reduced β-galactosidase activity suggesting that these features of the mRNA secondary structure may be essential for initiation of translation. Computer aided analysis of the potential structure of 290 mRNAs suggests these are conserved features of the initiation region.
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  • 20
    ISSN: 1573-5028
    Keywords: ABA ; Daucus carota ; ECP31 ; gene expression ; LEA clone ; somatic embryogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A full-length cDNA for ECP31, an embryogenic cell protein from carrot (Daucus carota L.) with a M r of 31000 (Kiyosue T, Satoh S, Kamada H, Harada H (1991) Plant Physiol 95: 1077–1083), was isolated from a cDNA library prepared from embryogenic cells using PCR-amplified DNA as a probe. The genomic Southern blot analysis revealed that there are two or three genes for ECP31 in the carrot genome. The transcripts of ECP31 accumulated in the peripheral regions of clusters of embryogenic cells and disappeared in the course of somatic embryogenesis that was induced by transfer of the embryogenic cells to auxin-free media. The cDNA encodes a polypeptide of 256 amino acids, and the calculated molecular weight of this polypeptide is 26 111. The deduced amino acid sequence shows a high degree (62.2%) of similarity to that of a protein that is abundant during late embryogenesis of cotton (LEA D34; Baker JC, Steele C, Dure III (1988) Plant Mol Biol 11: 227–291). The mRNAs for ECP31 started to accumulate in zygotic embryos at a late stage of embryogenesis but were undetectable in mature embryos within 24 h after imbibition of seeds. In dry fruits (seeds), the transcripts were detected only in zygotic embryos by in situ hybridization. The level of ECP31 transcripts increased after treatment with abscisic acid (ABA) in torpedo-shaped somatic embryos but not in seven-day-old seedlings. These results suggest that both embryo-specific factor(s) and ABA are involved in the expression of the gene for ECP31.
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  • 21
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    Plant molecular biology 19 (1992), S. 623-630 
    ISSN: 1573-5028
    Keywords: gene expression ; heat shock ; intron ; maize ; pollen ; RNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract While a heat shock treatment of 40 °C or 45 °C induced the vegetative tissues of maize to produce the typical heat shock proteins (HSPs), germinating maize pollen exposed to the same temperatures did not synthesize these characteristic HSPs. Comparison of RNA accumulation in shoot and tassel tissue showed that mRNAs for HSP70 and HSP18 increased several-fold, reaching high levels within 1 or 2 hours. At the higher temperature of 45 °C these vegetative tissues were blocked in removal of an intron from the HSP70 mRNA precursor, which accumulated to a high level in tassel tissue. In germinating pollen exposed to heat shock, mRNAs for these HSPs were induced but accumulated only to low levels. The stressed pollen maintained high levels of RNA for α-tubulin, a representative normal transcript. It is likely that the defective heat shock response of maize pollen is due to inefficient induction of heat shock gene transcription.
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  • 22
    ISSN: 1573-5028
    Keywords: gene duplication ; photosynthesis ; RFLP ; Southern blots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A second locus (Lhb1B) encoding Photosystem II Type I chlorophyll a/b-binding (CAB) polypeptides was identified in Arabidopsis thaliana. This locus carries two genes in an inverted orientation. The predicted sequences of the polypeptides encoded by these two genes show substantial divergence in their amino termini relative to each other and to the proteins encoded by the three Lhb1 CAB genes previously characterized [10], but little divergence within the predicted primary structure of the mature protein. DNA probes derived from seven additional types of tomato CAB genes, encoding chlorophyll a/b-binding polypeptides of several antenna systems of the photosynthetic apparatus, were tested against A. thaliana. Each of these hybridized in Southern blots to unique DNA fragment(s), demonstrating the existence of each of these different types of CAB genes in the genome of A. thaliana. The number of genes encoding each CAB type in A. thaliana was estimated to be similar to that of tomato.
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  • 23
    ISSN: 1573-5028
    Keywords: sunflower ; gene expression ; zygotic embryogenesis ; Lea proteins ; heat-shock proteins ; abscisic acid ; osmotic stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have cloned and sequenced three different cDNAs from sunflower seed-stored mRNA. Sequence similarities and response to heat-shock identified one of the cDNAs as a low-molecular-weight heat-shock protein (lmw-HSP). The other two clones showed significant sequence similarity to the cotton and carrot late-embryogenesis-abundant (Lea) proteins D-113 and Emb-1, respectively. The three cDNAs showed similar expression patterns during zygotic embryo development, as well as in vegetative tissues of 3-day-old seedlings in response to stress. Maximal accumulation of all three mRNAs was detected in dry seeds and during embryo mid-maturation stage, in the absence of exogenous stress. In seedlings, mRNAs accumulated to lower levels in response to osmotic stress and exogenous abscisic acid (ABA) treatments. A differential time course of response to osmotic stress was observed: lmw-HSP mRNA accumulation was induced earlier than that of Lea mRNAs. The coordinate accumulation of Lea and lmw-HSP transcripts during embryo development and in response to stress and ABA suggests the existence of common regulatory elements for Lea and lmw-HSP genes, and supports the notion that HSPs might have alternative functions in the plant cell.
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  • 24
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    Plant molecular biology 19 (1992), S. 1049-1055 
    ISSN: 1573-5028
    Keywords: Brassica napus ; rapeseed ; gene expression ; nucleotide sequence ; storage proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have isolated a five-member gene subfamily which encodes cruciferin, a legumin-like 12S storage protein of Brassica napus L., and have analyzed the structure and expression of the family members in developing embryos. Sequence analysis has shown that the coding regions of all five genes are highly similar, with the two most divergent members of the family retaining 89% sequence identity. The analysis of this cruciferin gene family's expression indicates that the developmental pattern of expression of each gene is similar, and the steady-state mRNA levels of each gene are approximately equivalent to each other at all developmental stages.
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  • 25
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    Plant molecular biology 20 (1992), S. 481-491 
    ISSN: 1573-5028
    Keywords: photosynthesis ; cytochrome b 6 ; gene regulation ; genome mapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The genes encoding the photosynthetic cytochrome b 6 (petB) and subunit 4 (petD) have been cloned and sequenced from the unicellular, photoheterotrophic, transformable cyanobacterium Synechococcus sp. PCC 7002, formerly designated Agmenellum quadruplicatum. The gene arrangement was found to be similar to that reported in the cyanobacterium Nostoc PCC 7906. The DNA and derived protein sequences were compared to chloroplast and the other cyanobacterial sequences. By pulsed-field electrophoresis, the petBD operon and the petCA operon, encoding the Rieske iron-sulfur protein and cytochrome f, were found to be located on separate, unlinked,Not I-digested DNA fragments. ThepetBD operon was found on the third largest Not I fragment (NC-325) while the petCA operon was found on the second largest Not I fragment (NB-370). These results suggest the two operons are not in proximity. The 1.35 kb transcript was shown to be light-regulated. Transcripts from cells grown under constant illumination showed a decrease in petB transcript levels to undetectable levels within 2 h after the cells were placed in the dark. Upon reillumination, transcript levels rose to three-fold over that seen initially under constant illumination.
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  • 26
    ISSN: 1573-5028
    Keywords: gene expression ; microsporogenesis ; Nicotiana tabacum ; pectate lyase ; pollen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A genomic clone has been isolated which contains an open reading frame of 1191 bp interrupted by two small introns. The ORF has been sequenced and the transcriptional start determined. The predicted amino acid sequence shows homology to the deduced amino acid sequences of two pollen-specific pectate lyase genes identified in tomato. The genomic clone was isolated using a partial cDNA clone, TP10, which had been isolated from a Nicotiana tabacum pollen cDNA library by means of differential screening. TP10 has been fully sequenced and contains an open reading frame of 792 bp which shows 96% homology to the ORF in the genomic clone. The transcript corresponding to TP10 is maximally expressed late in pollen development, and has not been detected in vegetative tissues.
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  • 27
    ISSN: 1573-5028
    Keywords: β-1,3-glucanase ; gene expression ; pathogenesis-related proteins ; plant-fungus interaction ; protein P14
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Tomato leaves infected by the fungal pathogen Cladosporium fulvum contain several types of intracellular and extracellular pathogenesis-related (PR) proteins. Previously, we reported the purification and serological characterization of five extracellular PR proteins: P2, P4, P6, a chitinase and a β-1,3-glucanase [22, 23]. Here we describe the purification of a basic intracellular 33 kDa β-1,3-glucanase and the isolation and characterization of cDNA clones encoding the two extracellular P14 isomers P4 and P6, the extracellular acidic β-1,3-glucanase and a basic 35 kDa β-1,3-glucanase, different from the purified 33 kDa protein. Southern blot analysis demonstrated that tomato PR proteins are not encoded by large gene families, as is the case in tobacco. The number of genes corresponding to each protein was estimated to vary between one and three. A northern blot analysis indicated that the mRNAs for the extracellular PR proteins (P4, P6 and acidic β-1,3-glucanase) accumulate to similar levels in compatible and incompatible tomato-C. fulvum interactions, although the maximum level of expression is reached much faster in the incompatible interaction. On the other hand, the mRNA for the basic 35 kDa β-1,3-glucanase is induced rapidly to high levels in both interactions, but declines in time to background levels only in the incompatible interaction. The relevance of this difference in relation to plant defence is discussed.
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  • 28
    ISSN: 1573-5028
    Keywords: aleurone ; Avena fatua ; cDNA nucleotide sequence ; gene expression ; gibberellin ; polyubiquitin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A λgt11 cDNA library, constructed from poly(A)+ mRNA isolated from Avena fatua aleurone layers incubated with 1 μM gibberellin A1 (GA1) for 4 days, was screened with an anti-idiotypic antiserum raised against the GA-specific monoclonal antibody MAC 182. One positive clone was isolated, sequenced and shown to encode a tetraubiquitin based on the deduced amino acid sequence. This polyubiquitin cDNA exhibited a high degree of homology to a cloned wheat hexaubiquitin in its 3′-non-coding region. Analysis of total RNA isolated from A. fatua aleurone layers, treated without or with a range of concentrations of GA1 from 10-11 to 10-6 M, by northern blotting using the cDNA probe revealed 8 different ubiquitin-containing transcript classes all of which are constitutively expressed in aleurone and are regulated by GA1.
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  • 29
    ISSN: 1573-5028
    Keywords: Cell division ; gene expression ; Nicotiana sylvestris ; protoplast ; stress ; ubiquitin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Four ubiquitin mRNA size classes were found to be differentially regulated in mesophyll protoplast-derived cultures of Nicotiana sylvestris. Three mRNA families of 1.9, 1.6 and 1.35 kb were expressed as soon as protoplasts were isolated. The 1.9 and 1.6 kb size classes were transiently expressed during the first hours of culture, whereas the level of expression of the 1.35 kb size class was maintained as long as cells kept dividing. A 0.7 kb mRNA size class started to be expressed just before the first divisions were observed. cDNAs corresponding to each of these families were isolated from a 6-h-old protoplast cDNA library and characterized. The 1.9, 1.6 and 1.35 kb mRNAs thus encode 7- or more, 6- and 5- mers, respectively, of ubiquitin whereas the 0.7 kb mRNAs encode a monomer of ubiquitin fused to a carboxyl extension protein of 52 amino acids. The expression of ubiquitin genes was studied, using probes specific for each of these transcript families, during protoplast culture and, for comparison, after various stresses including heat shock, HgCl2 treatment, a viral infection giving rise to a hypersensitive reaction, and an Agrobacterium tumefaciens infection which resulted in tumour formation. The 1.9 and 1.6 kb mRNA size classes were found to be stress-regulated, the 0.7 kb mRNA size class developmentally regulated and the 1.35 kb size class both stress- and developmentally regulated.
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  • 30
    ISSN: 1573-5028
    Keywords: β-D-glucuronidase ; mannopine synthase promoter ; Agrobacterium ; gene expression ; initiation of translation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Transcriptional and translational fusions between the reading frame of the β-D-glucuronidase gene (gusA) and the 2′ as well as the 1′ promoter of mannopine synthase (mas), a TR locus of Agrobacterium tumefaciens, were made. The expression of these constructs was studied in the transgenic F1 offspring of independent tobacco transformants at the protein level by assaying for GUS activity and western blot analysis of the GUS protein and at the steady-state mRNA level. In leaves, stems and roots no correlation was found between steady-state levels of GUS mRNA and enzyme activity. In older tissues significantly higher GUS activities were found. This is explained by the stable character of the GUS protein together with an accumulation of protein upon ageing. Three to ten times higher GUS activities were found for in vitro grown plants than for greenhouse-grown plants of the same offspring, despite similar levels of GUS mRNA. Roots from in vitro grown plants display three to ten times higher GUS activities than stems and leaves. In transgenic plants grown in vitro, containing a translational fusion with two AUGs in phase, the initiation of translation in leaf material occurred at both AUGs. Initiation of translation at the first AUG, however, was ten times more frequent. In contrast, initiation in roots from in vitro grown plants occurred exclusively at the second AUG.
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  • 31
    ISSN: 1573-5028
    Keywords: Agrobacterium ; binary vector ; CaMV 35S ; gene expression ; β-glucuronidase ; Nicotiana plumbaginifolia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A versatile gene expression cartridge and binary vector system was constructed for use in Agrobacterium-mediated plant transformation. The expression cartridge of the primary cloning vector, pART7, comprises of cauliflower mosaic virus Cabb B-JI isolate 35S promoter, a multiple cloning site and the transcriptional termination region of the octopine synthase gene. The entire cartridge can be removed from pART7 as a Not I fragment and introduced directly into the binary vector, pART27, recombinants being selected by blue/white screening for β-galactosidase. pART27 carries the RK2 minimal replicon for maintenance in Agrobacterium, the ColE1 origin of replication for high-copy maintenance in Escherichia coli and the Tn7 spectinomycin/streptomycin resistance gene as a bacterial selectable marker. The organisational structure of the T-DNA of pART27 has been constructed taking into account the right to left border, 5′ to 3′ model of T-DNA transfer. The T-DNA carries the chimaeric kanamycin resistance gene (nopaline synthase promoter-neomycin phosphotransferase-nopaline synthase terminator) distal to the right border relative to the lacZ′ region. Utilisation of these vectors in Agrobacterium-mediated transformation of tobacco demonstrated efficient T-DNA transfer to the plant genome.
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  • 32
    ISSN: 1573-5028
    Keywords: Chlamydomonas eugametos ; chlorophyll a/b-binding proteins ; circadian oscillator ; gene expression ; light-regulated genes
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    Topics: Biology
    Notes: Abstract In the green unicellular alga Chlamydomonas eugametos, cellular division is readily synchronized by light/dark cycles. Under these conditions, light initiates photosynthetic growth in daughter cells and begins the G1 phase. Genes whose expression is regulated upon illumination are likely to be important mechanisms controlling cell proliferation. To identify some of those genes, two cDNA libraries were prepared with poly(A)+ extracted from cells either stimulated with light for 1 h or held in darkness (quiescent cells) during the same period. To restrict our analysis to those genes that are part of the primary response, cells were incubated in presence of cycloheximide. Differential screening of approximately 40 000 clones in each library revealed 44 clones which hybridize preferentially with a [32P] cDNA probe derived from RNA of light-stimulated cells and 15 clones which react selectively with a [32P] cDNA probe synthesized from poly(A)+ RNA of quiescent cells. Cross-hybridization of these clones identified 4 independent sequences in the light-induced (LI) collection and 2 in the uninduced (LR) library. Four of these cDNAs correspond to mRNAs that are positively or negatively regulated upon activation of photosynthesis. One clone represents a mRNA that accumulates transitorily at both transitions. Finally, LI818 cDNA identifies a new chlorophyll a/b-binding (cab) gene family whose mRNA accumulation is controlled by light and a circadian oscillator. The endogenous timing system controls LI818 mRNA accumulation so that it precedes the onset of illumination by a few hours. On the other hand, light affects LI818 mRNA levels independently of active photosynthesis.
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  • 33
    ISSN: 1573-5028
    Keywords: Tomato ; gene expression ; wounding ; ethylene ; glycine-rich protein ; rRNA ; polyamines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Regulation of wound-inducible 1-aminocyclopropane-1-carboxylic acid (ACC) synthase expression was studied in tomato fruit (Lycopersicon esculentum cv. Pik-Red). A 70 base oligonucleotide probe homologous to published ACC synthase cDNA sequences was successfully used to identify and analyze regulation of a wound-inducible transcript. The 1.8 kb ACC synthase transcript increased upon wounding the fruit as well as during fruit ripening. Salicylic acid, an inhibitor of wound-responsive genes in tomato, inhibited the wound-induced accumulation of the ACC synthase transcript. Further, polyamines (putrescine, spermidine and spermine) that have anti-senescence properties and have been shown to inhibit the development of ACC synthase activity, inhibited the accumulation of the wound-inducible ACC synthase transcript. The inhibition by spermine was greater than that caused by putrescine or spermidine. The transcript level of a wound-repressible glycine-rich protein gene and that of the constitutively expressed rRNA were not affected as markedly by either salicylic acid or polyamines. These data suggest that salicylic acid and polyamines may specifically regulate ethylene biosynthesis at the level of ACC synthase transcript accumulation.
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  • 34
    ISSN: 1573-5028
    Keywords: adventitious buds ; cDNA cloning ; cytokinin ; gene expression ; germination ; Norway spruce
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A pulse treatment of embryos of Norway spruce with cytokinin suppresses germinative development and induces the coordinate formation of adventitious buds from subepidermal cell layers. To analyse the patterns of gene expression associated with germination and the alterations induced by the bud induction treatment, we have isolated cDNA clones corresponding to genes that are differentially expressed in cytokinin-treated and untreatedin vitro germinating embryos. One category of 14 clones hybridized to transcripts that were abundant specifically during germination. The expression of 8 of these genes was reduced by the bud induction treatment. Four clones, including one identified as a histone H2A gene, recognized transcripts that showed an increased abundance in bud-induced versusin vitro germinating embryos. A second category of 13 clones hybridized to transcripts that increased in abundance during post-germinative development of the seedling. Among these a subset of 8 clones, including an α-tubulin clone, corresponds to genes suppressed by the bud induction treatment, whereas 5 clones, including a gene with sequence similarity to polyubiquitin, were unaffected by the treatment. One clone hybridized to a message abundant in the seed, during early germination as well as in the vegetative bud, and showed 60% partial sequence identity to a barley (1→3)-β-glucanase gene. Genes expressed exclusively in bud-induced orin vitro germinating embryos were not found. The results show that a major difference in gene expression between treated and untreated embryos is related to the shift from extensive cell proliferation to elongation and differentiation that occurs at the transition from germination to post-germinative development, and which is suppressed in the bud-induced embryos.
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  • 35
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    Plant molecular biology 18 (1992), S. 749-757 
    ISSN: 1573-5028
    Keywords: salt stress ; stem-specific expression ; lipid transfer protein ; cDNA sequence ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A full-length tomato cDNA clone, TSW12, which is developmentally and environmentally regulated, has been isolated and characterized. TSW12 mRNA is accumulated during tomato seed germination and its level increases after NaCl treatment or heat shock. In mature plants, TSW12 mRNA is only detected upon treatment with NaCl, mannitol or ABA and its expression mainly occurs in stems. The nucleotide sequence of TSW12 includes an open reading frame coding for a basic protein of 114 amino acids; the first 23 amino acids exhibit the sequence characteristic of a signal peptide. The high similarity between the TSW12-deduced amino acid sequence and reported lipid transfer proteins suggests that TSW12 encodes a lipid transfer protein.
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  • 36
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    Plant molecular biology 18 (1992), S. 815-818 
    ISSN: 1573-5028
    Keywords: expression cassette ; gene expression ; protoplasts ; translation initiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Expression cassettes containing a duplicated cauliflower mosaic virus (CaMV) 35S promoter fused to a polylinker preceded by the CCACCATGG and AACAATGG sequences were constructed. These two sequences correspond to the consensus sequences around the translation start codons in vertebrates and plants respectively. Translational fusions were made with the β-glucuronidase-coding sequence and transient expression was recorded in tobacco mesophyll protoplasts. Approximately three times more GUS activity was found in protoplasts incubated with the constructs harbouring translational fusions as compared to a control harbouring a transcriptional fusion. No significant difference was observed between GUS activities obtained with the two consensus sequences.
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  • 37
    ISSN: 1573-5028
    Keywords: glucanase ; gene expression ; pathogenesis response ; stress response ; plant growth regulators ; gene family
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    Topics: Biology
    Notes: Abstract A rice β-glucanase gene was sequenced and its expression analyzed at the level of mRNA accumulation. This gene (Gns1) is expressed at relatively low levels in germinating seeds, shoots, leaves, panicles and callus, but it is expressed at higher levels in roots. Expression in the roots appears to be constitutive. Shoots expressGns1 at much higher levels when treated with ethylene, cytokinin, salicylic acid, and fungal elicitors derived from the pathogenSclerotium oryzae or from the non-pathogenSaccharomyces cereviseae. Shoots also expressGns1 at higher levels in response to wounding. Expression in the shoots is not significantly affected by auxin, gibberellic acid or abscisic acid. The β-glucanase shows 82% amino acid similarity to the barley 1,3;1,4-β-D-glucanases, and from hybridization studies it is the β-glucanase gene in the rice genome closest to the barley 1,3;1,4-β-glucanase EI gene. The mature peptide has a calculated molecular mass of 32 kDa. The gene has a large 3145 bp intron in the codon for the 25th amino acid of the signal peptide. The gene exhibits a very strong codon bias of 99% G+C in the third position of the codon in the mature peptide coding region, but only 61% G+C in the signal peptide region.
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  • 38
    ISSN: 1573-5028
    Keywords: cDNA sequence ; gene expression ; glutamine synthetase ; phytochrome ; Solanaceae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A full-length cDNA encoding glutamine synthetase (GS) was cloned from a λgt10 library of tobacco leaf RNA, and the nucleotide sequence was determined. An open reading frame accounting for a primary translation product consisting of 432 amino acids has been localized on the cDNA. The calculated molecular mass of the encoded protein is 47.2 kDa. The predicted amino acid sequence of this precursor shows higher homology to GS-2 protein sequences from other species than to a leaf GS-1 polypeptide sequence, indicating that the cDNA isolated encodes the chloroplastic isoform (GS-2) of tobacco GS. The presence of C-and N-terminal extensions which are characteristic of GS-2 proteins supports this conclusion. Genomic Southern blot analysis indicated that GS-2 is encoded by a single gene in the diploid genomes of both tomato and Nicotiana sylvestris, while two GS-2 genes are very likely present in the amphidiploid tobacco genome. Western blot analysis indicated that in etiolated and in green tomato cotyledons GS-2 subunits are represented by polypeptides of similar size, while in green tomato leaves an additional GS-2 polypeptide of higher apparent molecular weight is detectable. In contrast, tobacco GS-2 is composed of subunits of identical size in all organs examined. GS-2 transcripts and GS-2 proteins could be detected at high levels in the leaves of both tobacco or tomato. Lower amounts of GS-2 mRNA were detected in stems, corolla, and roots of tomato, but not in non-green organs of tobacco. The GS-2 transcript abundance exhibited a diurnal fluctuation in tomato leaves but not in tobacco leaves. White or red light stimulated the accumulation of GS-2 transcripts and GS-2 protein in etiolated tomato cotyledons. Far-red light cancelled this stimulation. The red light response of the GS-2 gene was reduced in etiolated seedlings of the phytochrome-deficient aurea mutant of tomato. These results indicate a phytochrome-mediated light stimulation of GS-2 gene expression during greening in tomato.
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  • 39
    ISSN: 1573-5028
    Keywords: cab gene ; chlorophyll a/b-binding protein ; gymnosperm ; gene expression ; pine (Pinus thunbergii)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A gene for chlorophyll a/b-binding protein (cab) of pine (Pinus thunbergii) was isolated and sequenced. The gene (cab-6) contains an intron at a position equivalent to the type II cab genes of angiosperms. Transcript mapping analyses show that the amount of the mRNA in the dark is about half of that in the light. The cab-6 gene is expressed in dark-grown seedlings at a very high level, differing from angiosperm cab genes which are induced by light. The cab-6 gene typifies the coniferous plant cab genes in light-independent gene expression.
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  • 40
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    Plant molecular biology 19 (1992), S. 1031-1044 
    ISSN: 1573-5028
    Keywords: ABA ; dehydrin ; gene expression ; pea (Pisum sativum L.) ; seed development ; water stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An antiserum raised against dehydrin from maize (Zea mays) recognised several polypeptides in extracts of pea (Pisum sativum) cotyledons. A cDNA expression library was prepared from mRNA of developing cotyledons, screened with the antiserum and positive clones were purified and characterised. The nucleotide sequence of one such clone, pPsB12, contained an open reading frame which would encode a polypeptide with regions of significant amino acid sequence similarity to dehydrins from other plant species. The deduced amino acid sequence of the pea dehydrin encoded by B12 is 197 amino acids in length, has a high glycine content (25.9%), lacks tryptophan and is highly hydrophilic. The polypeptide has an estimated molecular mass of 20.4 kDa and pI=6.4. An in vitro synthesised product from the clone comigrates with one of the in vivo proteins recognised by the antiserum. A comparison of the pea dehydrin sequence with sequences from other species revealed conserved amino acid regions: an N-terminal DEYGNP and a lysine-rich block (KIKEKLPG), both of which are present in two copies. Unexpectedly, pea dehydrin lacks a stretch of serine residues which is conserved in other dehydrins. B12 mRNA and dehydrin proteins accumulated in dehydration-stressed seedlings, associated with elevated levels of endogenous abscisic acid (ABA). Applied ABA induced expression of dehydrins in unstressed seedlings. Dehydrin expression was rapidly reversed when seedlings were removed from the stress or from treatment with ABA and placed in water. During pea cotyledon development, dehydrin mRNA and proteins accumulated in mid to late embryogenesis. Dehydrin proteins were some of the most actively synthesised at about the time of maximum fresh weight and represent about 2% of protein in mature cotyledons.
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  • 41
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    Plant molecular biology 18 (1992), S. 1-11 
    ISSN: 1573-5028
    Keywords: betaine aldehyde dehydrogenase ; gene expression ; glycine betaine ; osmotic stress ; salt tolerance ; sugar beet
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Members of the Chenopodiaceae, such as sugar beet and spinach, accumulate glycine betaine in response to salinity or drought stress. The last enzyme in the glycine betaine biosynthetic pathway is betaine aldehyde dehydrogenase (BADH). In sugar beet the activity of BADH was found to increase two- to four-fold in both leaves and roots as the NaCl level in the irrigation solution was raised from 0 to 500 mM. This increase in BADH activity was paralleled by an increase in level of translatable BADH mRNA. Several cDNAs encoding BADH were cloned from a λgt10 libary representing poly(A)+ RNA from salinized leaves of sugar beet plants, by hybridization with a spinach BADH cDNA. Three nearly full-length cDNA clones were confirmed to encode BADH by their nucleotide and deduced amino acid sequence identity to spinach BADH; these clones showed minor nucleotide sequence differences consistent with their being of two different BADH alleles. The clones averaged 1.7 kb and contained an open reading frame predicting a polypeptide of 500 amino acids with 83% identity to spinach BADH. RNA gel blot analysis of total RNA showed that salinization to 500 mM NaCl increased BADH mRNA levels four-fold in leaves and three-fold in the taproot. DNA gel blot analyses indicated the presence of at least two copies of BADH in the haploid sugar beet genome.
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  • 42
    ISSN: 1573-5028
    Keywords: ribosomal protein S15a ; cDNA clones ; rapessed ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have isolated two cDNA clones which appear to encode the 40S ribosomal subunit protein S15a from Brassica napus (oilseed rape). The open reading frame in both clones contains 390 bases, encoding a deduced polypeptide sequence of 130 amino acids (100% homology between clones) with 76% sequence identity to the N-terminal 37 amino acids of the rat ribosomal protein S15a and 80% identity to the S24 polypeptide of yeast. Both the yeast and rapeseed proteins have a net positive charge of +9 and the rapeseed S15a protein has a molecular mass of 14778 Da compared to 14762 Da for the yeast protein. The rapeseed ribosomal protein S15a is encoded by a small multi-gene family with at least two actively transcribed members. A single transcript of ca. 1.0 kb, corresponding to ribosomal protein S15a, is abundant in actively dividing tissues such as apical meristem, flower buds and young leaves and less abundant in mature stem and fully expanded leaves.
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  • 43
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    Plant molecular biology 19 (1992), S. 217-230 
    ISSN: 1573-5028
    Keywords: chlorophyll a/b-binding protein genes ; Glycine ; LHCP II ; photosynthesis ; soybean ; ribulose-1,5-bisphosphate carboxylase genes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The levels of chlorophyll a/b-binding protein (Cab) gene polysomal poly(A)+ mRNA were quantitated throughout the development of Glycine max L. Cab mRNAs were abundant in young expanding leaves, representing 6.1% of the leaf mRNA population. Lower Cab mRNA levels were present in embryos, stems, and cotyledons of developing seedlings; the lowest levels were found in roots where they accounted for 0.04% of the polysomal poly(A)+ mRNA of this organ. To determine the contribution of different members of the Cab gene family to the Cab mRNA populations, a quantitative S1 nuclease reconstruction assay was developed. Cab3, Cab4, and Cab5 mRNAs were detected in all stages examined during soybean development but their levels underwent differential changes. Cab3 encodes the most abundant Cab mRNA in young leaves, developing embryos, and in Stage VII cotyledons from the developing soybean seedling. The levels of Cab mRNAs were compared to the levels of ribulose-1,5-bisphosphate carboxylase small subunit gene mRNA and differences in their patterns of accumulation were noted. Collectively these data indicate that during soybean embryogenesis developmental control mechanisms supersede light-regulatory signals.
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  • 44
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    Plant molecular biology 19 (1992), S. 959-971 
    ISSN: 1573-5028
    Keywords: gene expression ; gene variants ; pre-mRNA splicing ; pseudogenes ; U1 small nuclear RNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract U1 small nuclear RNAs (U1snRNAs) occur in the nucleus of plants and animals where, complexed with several proteins in the form of U1 small nuclear ribonucleoprotein particles (U1snRNPs), they play an important role in precursor messenger RNA (pre-mRNA) splicing. Ten potato U1snRNA genes have been isolated on two genomic clones illustrating the clustering of this multigene family on the potato genome. Based on both the sequence of their coding regions and upstream regulatory elements, seven of the genes are potentially functional. The other three genes were pseudogenes with defective promoter or coding region sequences. Analysis of expression of individual cloned U1snRNA genes in transfected tobacco protoplasts was impossible due to the similarity of U1snRNA sequences in tobacco. However, by marking the coding regions with oligonucleotides or constructing chimaeric genes consisting of a potato U1snRNA promoter region and maize U5snRNA coding region, three of the U1 promoter regions were shown to be transcriptionally active.
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  • 45
    ISSN: 1573-5028
    Keywords: gene expression ; promoter specificity ; snRNA gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have demonstrated recently that the genes encoding the U3 small nuclear RNA (snRNA) in dicot plants are transcribed by RNA polymerase III (pol III), and not RNA polymerase II (pol II) as in all other organisms studied to date. The U3 gene was the first example of a gene transcribed by different polymerases in different organisms. Based on phylogenetic arguments we proposed that a polymerase specificity change of the U3 snRNA gene promoter occurred during plant evolution. To map such an event we are examining the U3 gene polymerase specificity in other plant species. We report here the characterization of a U3 gene from wheat, a monocot plant. This gene contains the conserved promoter elements, USE and TATA, in a pol III-specific spacing seen also in a wheat U6 snRNA gene characterized in this report. Both the U3 and the U6 genes possess typical pol III termination signals but lack the cis element, responsible for 3′-end formation, found in all plant pol II-specific snRNA genes. In addition, expression of the U3 gene in transfected maize protoplasts is less sensitive to α-amanitin than a pol II-transcribed U2 gene. Based on these data we conclude that the wheat U3 gene is transcribed by pol III. This observation suggests that the postulated RNA polymerase specificity switch of the U3 gene took place prior to the divergence of angiosperm plants into monocots and dicots.
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  • 46
    ISSN: 1573-5028
    Keywords: ADP-glucose pyrophosphorylase ; Anabaena 7120 ; Escherichia coli ; gene cloning ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Previous studies have indicated that ADP-glucose pyrophosphorylase (ADPGlc PPase) from the cyanobacteriumAnabaena sp. strain PCC 7120 is more similar to higher-plant than to enteric bacterial enzymes in antigenicity and allosteric properties. In this paper, we report the isolation of theAnabaena ADPGlc PPase gene and its expression inEscherichia coli. The gene we isolated from a genomic library utilizes GTG as the start codon and codes for a protein of 48347 Da which is in agreement with the molecular mass determined by SDS-PAGE for theAnabaena enzyme. The deduced amino acid sequence is 63, 54, and 33% identical to the rice endosperm small subunit, maize endosperm large subunit, and theE. coli sequences, respectively. Southern analysis indicated that there is only one copy of this gene in theAnabaena genome. The cloned gene encodes an active ADPGlc PPase when expressed in anE. coli mutant strain AC70R1-504 which lacks endogenous activity of the enzyme. The recombinant enzyme is activated and inhibited primarily by 3-phosphoglycerate and Pi, respectively, as is the nativeAnabaena ADPGlc PPase. Immunological and other biochemical studies further confirmed the recombinant enzyme to be theAnabaena enzyme.
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  • 47
    ISSN: 1573-5028
    Keywords: gene expression ; desaturation ; oil synthesis ; embryogenesis ; stearoyl-acyl carrier protein desaturase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nucleotide sequence is reported for a cDNA containing the entire coding region of a stearoyl-ACP desaturase (EC 1.14.99.6) fromBrassica napus L. cv. Jet neuf. The cDNA was obtained from a library constructed from poly(A)+ RNA purified from embryo tissue. The derived amino acid sequence demonstrates substantial similarity with those from other plant Δ9-desaturases. Comparative RNA-dot blot analyses using the Δ9-desaturase cDNA and a rapessed oleosin cDNA as probes showed that although both these transcripts were seed-specific, they exhibited distinct patterns of temporal regulation. The desaturase message was induced by 25 days after anthesis (DAA), peaking at 45 DAA but decreasing considerably thereafter. In contrast, the oleosin transcript did not increase until 45–50 DAA, reaching a peak much later at about 70 DAA.
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  • 48
    ISSN: 1573-5028
    Keywords: barley (Hordeum vulgare) ; zygotic embryogenesis ; plant development ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The temporal and spatial pattern of expression of a novel barley gene is described. The gene has been identified through the differential screening of a cDNA library constructed to poly(A)+ RNA of zygotic embryos. Transcripts corresponding to the cDNA, pZE40, become abundant in the non-axial tissues of the developing embryo within 8–10 days after anthesis, when steady-state levels are high in the scutellum, coleoptile and coleorhiza, with the exception of the scutellar epithelium. This expression pattern is maintained throughout maturation of the embryo until levels eventually decline as the grain desiccates. On germination, there is a transient re-appearance of mRNA to pZE40, with accumulation specifically restricted to the scutellum of the seedling. In situ hybridization has enabled the detection of transcripts elsewhere in the barley plant, in highly localized groups of cells. The timing and cell specificity of expression suggests the gene product is involved in the synthesis and/or transport of metabolites.
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  • 49
    ISSN: 1573-5028
    Keywords: S-adenosylmethionine decarboxylase ; differential screening ; gene expression ; Solanum tuberosum ; tuberisation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract cDNA clones of two genes (TUB8 and TUB13) which show a 25–30-fold increase in transcript in the stolon tip during the early stages of tuberisation, have been isolated by differential screening. These genes are also expressed in leaves, stems and roots and the expression pattern in these organs changes on tuberisation. Southern analysis shows homologous sequences in the non-tuberising wild type potato species Solanum brevidens and in Lycopersicon esculentum (tomato). Sequence analysis reveals a high degree of similarity between the TUB13 cDNA, and a human S-adenosylmethionine decarboxylase gene. The predicted TUB8 peptide sequence shows several repeats of alanine, glutamate and proline which suggests a structural role for the encoded protein.
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  • 50
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    Plant molecular biology 20 (1992), S. 663-671 
    ISSN: 1573-5028
    Keywords: PEP carboxylase ; housekeeping gene ; gene expression ; gene structure ; light-mediated activation ; Saccharum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A gene (SCPEPCD1) encoding phosphoenolpyruvate carboxylase (PEPC) was isolated from the C-4 monocot sugarcane (Saccharum hybrid var. H32-8560). SCPEPCD1 is ca. 6800 bp long, with 10 exons. The entire gene sequence from −1561 to 262 bp downstream of the putative poly(A) addition signal is reported. A low-level, essentially constitutive pattern of expression, amino acid sequence similarities to other ‘housekeeping’ PEPC enzymes, and the absence of DNA sequence elements conserved in the upstream region of maize and sorghum C-4-specific PEPC genes indicate that SCPEPCD1 encodes a housekeeping PEPC. Despite this, a motif proposed to act as a phosphorylation site in light-mediated activation of photosynthetic PEPC enzymes [10] is present in the SCPEPCD1 protein; evidence is presented for the presence of this site in other housekeeping PEPC proteins.
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  • 51
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    Plant molecular biology 20 (1992), S. 705-713 
    ISSN: 1573-5028
    Keywords: alanine aminotransferase ; C4 photosynthesis ; gene expression ; nucleotide sequencing ; Panicum miliaceum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have determined the nucleotide sequence of a cDNA encoding AlaAT-2, which is believed to function in the C4-pathway of Panicum miliaceum. An open reading frame (1446 bp) encodes a protein of 482 amino acid residues. The deduced amino acid sequence of AlaAT-2 shows 44.2 and 44.8% homology with the amino acid sequences of AlaATs from rat and human livers, respectively. Northern blot analysis showed that the gene encoding AlaAT-2 in mesophyll and bundle sheath cells was the same and transcribed similarly in the cells. The level of translatable mRNA for AlaAT-2 increased dramatically during greening.
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  • 52
    ISSN: 1573-5028
    Keywords: chloroplast ; gene expression ; photosystem 2 ; transcription ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The time course of the accumulation of the transcripts from 13 psb genes encoding a major part of the proteins composing photosystem II during light-induced greening of dark-grown wheat seedlings was examined focusing on early stages of plastid development (0.5 h through 72 h). The 13 genes can be divided into three groups. (1) The psbA gene is transcribed as a single transcript of 1.3 kb in the dark-grown seedlings, but its level increases 5- to 7-fold in response to light due to selective increase in RNA stability as well as in transcription activity. (2) The psbE-F-L-J operon, psbM and psbN genes are transcribed as a single transcript of 1.1 kb, two transcripts of 0.5 and 0.7 kb and a single transcript of 0.3 kb, respectively, in the dark-grown seedlings. The levels of accumulation of every transcript remain unchanged or rather decrease during plastid development under illumination. (3) The psbK-I-D-C gene cluster and psbB-H operon exhibit fairly complicated northern hybridization patterns during the greening process. When a psbC or psbD gene probe was used for northern hybridization, five transcripts differing in length were detected in the etioplasts from 5-day old dark-grown seedlings. After 2 h illumination, two new transcripts of different length appeared. Light induction of new transcripts was also observed in the psbB-H operon.
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  • 53
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    The journal of membrane biology 126 (1992), S. 265-275 
    ISSN: 1432-1424
    Keywords: photosynthesis ; thylakoids ; electrochromism ; gramicidin ; conductance ; dimerization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The effect of the pore-forming antibiotic gramicidin on pure lipid membranes is well characterized. We studied its action in protein-rich thylakoid membranes that contain less than 25% (wt/wt) acyl lipids. A transmembrane voltage was induced by flashing light, and its decay was measured and interpreted to yield the distribution of gramicidin over thylakoids, its dimerization constant and its single-channel conductance in this membrane. The distribution of gramicidin over the ensemble of thylakoids was immediately homogeneous when the antibiotic was added under stirring, while it became homogeneous only after 20 min in a stirred suspension that was initially heterogeneous. The dimerization constant, 5×1014 cm2/mol, was about 10 times larger than in pure lipid membranes. This was attributed to the upconcentration of gramicidin in the small fractional area of protein free lipid bilayer and further by a preference of gramicidin for stacked portions of the membrane. The latter bears important consequences with regard to bioenergetic studies with this ionophore. As gramicidin was largely dimerized from a concentration of 1 nm (in the suspension) on, the membrane's conductance then increased linearly as a function of added gramicidin. When the negative surface potential at the thylakoid membrane was screened, the conductance of a single gramicidin dimer agreed well with figures reported for bilayers from neutral lipid (about 0.5 pS at 10 mm NaCl). The modulation of the conductance by the surface potential in spinach versus pea thylakoids and between different preparations is discussed in detail.
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  • 54
    ISSN: 1871-4528
    Keywords: water-stress ; photosynthesis ; yield
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Relations between measurements of the slow kinetics of chlorophyll fluorescence and growth and yield were examined in seven potato genotypes grown either fully irrigated or droughted from the time of plant emergence. Drought reduced total dry matter production and yields and increased tuber dry matter concentration. Drought increased harvest index in cv. Spunta, but decreased it in cv. Pentland Crown. Total dry matter production was correlated with each of constant fluorescence, variable fluorescence and the half life of the decay in variable fluorescence. These correlations were determined largely by the effect of treatment, and did not discriminate effectively between genotypes within a treatment.
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  • 55
    ISSN: 1871-4528
    Keywords: water-stress ; photosynthesis ; leaf water potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The slow kinetics of chlorophyll fluorescence were examined in seven potato genotypes grown either fully irrigated or droughted from the time of plant emergence. Constant and variable fluorescence (F o andF v respectively) declined with time in plants from both irrigated and droughted treatments, but the decline was greater in droughted than irrigated plants. However, the yield of variable fluorescence (F v/(F o+F v)) was unaffected by the drought treatment. The main effect of drought was upon the quenching of variable fluorescence. Both the half life of the decay of variable fluorescence (q1/2) and the secondary maximum (M) were significantly greater in the droughted plants than in those from the irrigated treatment. Significant differences between genotypes were found forF v/(F o+F v),M andq 1/2. Genotype-by-treatment interactions were non-significant for all the variables examined. Changes in chlorophyll fluorescence transients were not closely related to changes in leaf water potential.
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  • 56
    ISSN: 1871-4528
    Keywords: benzylaminopurine ; gibberellic acid ; senescence ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The modifying effects of applying the plant growth regulators (PGRs) benzylaminopurine (BAP), gibberellic acid (GA3) and BAP+GA3 on physiological age were studied. Two experiments with two cultivars, differing in rate of physiological ageing (medium-early Pampeana, medium-late Huinkul) and two storage systems were performed during 1988/89 and 1989/90 in two different potato areas of Argentina. In both seasons seed tubers stored in heaps reached an advanced physiological age at planting, compared with tubers from the cold store. Seed tubers of cv. Pampeana were older than those of Huinkul. compared with control crops, those sprayed with BAP maintained ground cover and photosynthesis for longer, and those sprayed with GA3 for a shorter period. Consequently tuber yield was decreased by GA3 in 1988/89, but in 1989/90 all crops treated with PGRs outyielded the control. BAP could overcome effects of advanced physiological age on crop senescence and tuber yield.
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  • 57
    ISSN: 1573-9368
    Keywords: transgenic mice ; gene expression ; mammary gland ; co-injection ; milk protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In an attempt to enhance the frequency and level of expression of a poor-performing MMTV-driven transgene, we co-integrated this construct with the ovine β-lactoglobulin (BLG) gene in transgenic mice. Seven lines of transgenic mice possessing co-integrated BLG and MMTV-RZ5 transgenes were compared with 12 lines of mice that possessed only the MMTV-RZ5 construct. Co-integration enhanced the frequency of expression in the mammary gland from two out of 12 lines for the MMTV-RZ5 transgene alone, to five out of seven when co-integrated with BLG. Surprisingly, co-integration also resulted in co-expression of the two transgenes in the salivary gland, lung and spleen in addition to the mammary gland. Furthermore, both transgenes were expressed in virgin animals, and throughout pregnancy and lactation, suggesting that the developmental regulation of the locus follows that of the MMTV-promoter. These findings represent a novel locus control property of the ovine BLG gene that confer s commitment of the locus to the mammary gland, but also to a range of heterogeneous tissues possibly defined by the second promoter at the locus
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  • 58
    ISSN: 1573-9368
    Keywords: transgenic rabbits ; gene expression ; mammary gland ; erythropoietin ; WAP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An understanding of the expression of transgenes in the mammary gland during gestation and lactation is crucial for the use of transgenic mammals as bioreactors. Here we describe the temporal pattern of expression of the endogenous rabbit WAP gene and human erythropoietin (hEPO) transgenes under the control of rabbit WAP promoter and 3′ flanking sequences. The endogenous rabbit WAP gene was expressed throughout gestation including the day of mating, as well as during lactation in transgenic rabbits bearing a minigene construct. In non-pregnant cycling females, WAP expression was found independent of transgenic status; however, WAP expression was not detected in non-cycling females. The significance of this new finding is not clear at present. hEPO mRNA was detected in mammary gland biopsies from pregnant transgenic rabbits only on day 28 of gestation. During lactation, transcripts were present in mammary gland biopsy samples taken on days 0, 7, 14 and 21. A sharp decline in the levels ...
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  • 59
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    Journal of applied phycology 10 (1998), S. 547-554 
    ISSN: 1573-5176
    Keywords: herbicide ; green alga ; growth ; nutrients ; photosynthesis ; it Protosiphon botryoides ; respiration ; Thiobencarb
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of the herbicide thiobencarb (Saturn) were tested on the growth and physiology of the chlorophyte Protosiphon botryoides isolated from an Egyptian paddy. Assays were conducted using 16-day batch cultures. Chlorophyll and dry weight biomass yields were significantly reduced at 2–3 mg L-1 thiobencarb, and dark respiration increased and protein decreased significantly at 3 mg L-1. Reductions in exponential specific growth rate (μ) were generally small, but in some cases significant. Thiobencarb also slightly, but significantly, reduced the 77 K fluorescence parameter Fv/Fm, an indicator of maximum photosynthetic efficiency. No consistent dose-dependent changes occurred in chlorophyll per unit dry weight, total carbohydrate or gross photosynthetic capacity. Whereas half of the added thiobencarb was recovered from control (uninoculated) medium, it was largely absent from cells and culture medium after sixteen days, indicating biodegradation by the alga or associated bacteria. P. botryoides recovered fully within sixteen days following subculture in thiobencarb-free medium. Independently varying phosphate and nitrate nine-fold had no clear effect on the sensitivity of P. botryoides to thiobencarb.
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  • 60
    ISSN: 1573-5176
    Keywords: Cyanobacterium ; Spirulina platensis ; Arthrospira ; CO2 ; organic carbon ; nitrogen ; photosynthesis ; batch culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The consequences of the addition of CO2 (1%) in cultures of S. platensis are examined in terms of biomass yield, cell composition and external medium composition. CO2 enrichment was tested under nitrogen saturating and nitrogen limiting conditions. Increasing CO2 levels did not cause any change in maximum growth rate while it decreased maximum biomass yield. Protein and pigments were decreased and carbohydrate increased by high CO2, but the capability to store carbohydrates was saturated. C:N ratio remained unchanged while organic carbon released to the external medium was enhanced, suggesting that organic carbon release in S. platensis is an efficient mechanism for the maintenance of the metabolic integrity, balancing the cell C:N ratio in response to environmental CO2 changes. CO2 affected the pigment content: Phycocyanin, chlorophyll and carotenoids were reduced in around 50%, but the photosynthetic parameters were slightly changed. We propose that in S. platensis CO2 could act promoting degradation of pigments synthetised in excess in normal CO2 conditions, that are not necessary for light harvesting. Nitrogen assimilation was significantly not affected by CO2, and it is proposed that the inability to stimulate N assimilation by CO2 enrichment determined the lack of response in maximum growth rate.
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  • 61
    ISSN: 1573-5176
    Keywords: adaptation ; β-carotene ; Dunaliella salina ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photosynthetic characteristics of Dunaliella salina with high (red form) and low β-carotene (green form) concentrations were studied. D. salina growing in brine saltworks exhibited a high level of β-carotene (15 pg cell−1). The rate of oxygen evolution as a function of irradiance was higher in the red than in the green form (on chlorophyll basis). Photosynthetic inhibition of the green form was observed above 500 µmol m−2 s−1. The red form appeared more resistant to high irradiance and no inhibition in O2 evolution was observed up 2000 µmol m−2 s−1. However, when these results are expressed on a cell number basis the rate of oxygen evolution was significantly higher in the green form. Carbonic anhydrase (CA) activity (total, soluble, membrane bound) was found in red and green forms. CA was higher in the red form on a chlorophyll basis, but lower if expressed on a protein basis. The light dependent rate of oxygen evolution and photoinhibition depends on the concentration of β-carotene in D. salina cells.
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  • 62
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    Journal of applied phycology 10 (1998), S. 419-425 
    ISSN: 1573-5176
    Keywords: Gracilaria cornea ; photosynthesis ; respiration ; chlorophyll ; phycoerythrin ; Florida ; salinity ; temperature ; irradiance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The agarophyte Gracilaria cornea, collected over 2.5 y in the Florida Keys, shows adaptations to oceanic salinities and subtropical to tropical water temperatures in its photosynthetic and respiratory responses as measured with a respirometer. No seasonal pattern in responses to irradiance, temperature, and salinity were evident between five collections over a 20-month period, indicating the tropical nature of the populations from Bahia Honda and Pigeon Keys. Concentrations of chlorophyll a (0.09 to 0.41 mg g d wt-1) and phycoerythrin (0.06 to 0.36 mg g d wt- 1) were low and reflect the low nutrient regime of the habitats, especially when compared to laboratory cultured plants. Compensation and saturation irradiances were also low (11–38 and 90–127 μmol photon m-2 s-1), indicating acclimation to lower irradiances in their shallow (1–2 m depth) habitats where turbidity can be high. In comparison with other subtropical and warm temperate species of Gracilaria, G. cornea had lower levels of pigment, but similarly high photosynthetic efficiency, demonstrating shade adaptation; it had only limited tolerance to salinities below 20‰ and temperatures below 15 °C. Thus, G. cornea from the Florida Keys in mariculture would require subtropical to tropical temperatures and stable oceanic salinities.
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  • 63
    ISSN: 1573-5176
    Keywords: Chlorophyll antenna size ; damage and repair cycle ; photon use efficiency ; photosynthesis ; photoinhibition ; Dunaliella salina
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The photon use efficiencies and maximal rates of photosynthesis in Dunaliella salina (Chlorophyta) cultures acclimated to different light intensities were investigated. Batch cultures were grown to the mid-exponential phase under continuous low-light (LL: 100 μmol photon m-2 s-1) or high-light (HL: 2000 μmol photon m-2 s-1) conditions. Under LL, cells were normally pigmented (deep green) containing ∼500 chlorophyll (Chl) molecules per photosystem II (PSII) unit and ∼250 Chl molecules per photosystem I (PSI). HL-grown cells were yellow-green, contained only 60 Chl per PSII and 100 Chl per PSI and showed signs of chronic photoinhibition, i.e., accumulation of photodamaged PSII reaction centers in the chloroplast thylakoids. In LL-grown cells, photosynthesis saturated at ∼200 μmol photon m-2 s-1 with a rate (Pmax) of ∼100 mmol O2 (mol Chl)-1 s-1. In HL-grown cells, photosynthesis saturated at much higher light intensities, i.e. ∼2500 μmol photon m-2 s-1, and exhibited a three-fold higher Pmax (∼300 mmol O2 (mol Chl)-1 s-1) than the normally pigmented LL-grown cells. Recovery of the HL-grown cells from photoinhibition, occurring prior to a light-harvesting Chl antenna size increase, enhanced Pmax to ∼675 mmol O2 (mol Chl)-1 s-1. Extrapolation of these results to outdoor mass culture conditions suggested that algal strains with small Chl antenna size could exhibit 2–3 times higher productivities than currently achieved with normally pigmented cells.
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  • 64
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    Journal of applied phycology 4 (1992), S. 1-9 
    ISSN: 1573-5176
    Keywords: photobioreactor ; flat plate air-lift reactor ; Chlorella ; Synechococcus ; hydraulic characteristics ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A flat plate, multi-pass air lift reactor (FPALR) for the culture of photosynthetic organisms was constructed from twin wall acrylic sheet and its performance characterised. When operated at an air input of 2.01 min−1 the multi-pass system had a Reynolds number of 5200 indicating fully turbulent flow. Chlorella vulgaris 211/11c was found to have a stationary phase biomass of 1.48 g 1−1 when grown in the flat plate air lift reactor (FPALR) at 100 µmol m−2s−1 compared to 1.11 g 1−1 when cultured in the continually stirred tank reactor (CSTR) at the same PFD (photon flux density). The same organism cultured at 200 µmol m−2s−1 achieved a stationary phase biomass of 1.71 g 1−1 in the FPALR. In contrast, Scenedesmus sp. produced a stationary phase biomass of 2.27 g1−1 and 1.27 g1−1, when cultured at 100 µmol m−2s−1 in the FPALR and the CSTR respectively. The growth rates of both organisms were also higher in the PFALR.
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  • 65
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    Journal of applied phycology 10 (1998), S. 51-53 
    ISSN: 1573-5176
    Keywords: blue-green alga ; cyanobacterium ; Fv/Fmlight ; Nostoc flagelliforme ; photosynthesis ; rewetting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract PS II photochemical efficiency (Fv/Fm) of Nostoc flagelliforme was examined after rewetting in order to investigate the light-dependency of its photosynthetic recovery. Fv/Fm was not detected in the dark, but was immediately recognized in the light. Different levels of light irradiation (4, 40 and 400 µmol photon m2 s-1) displayed different effects on the recovery process of photosynthesis. The intermediate level led to the best recovery of photochemical efficiency; the low light required longer and the high light inhibited the extent of the recovered efficiency. It was concluded that the photosynthetic recovery of N. flagelliforme is both light-dependent and influenced by photon flux density.
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  • 66
    ISSN: 1573-5176
    Keywords: ammonium ; C:N ratio ; tank culture ; dietary fibre ; fatty acids ; nitrogen ; photosynthesis ; Ulva rigida
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Physiological and biochemical changes in relation to inorganic nitrogen availability were studied for tank-cultivated Ulva rigida grown under nitrogen- enriched and nitrogen-depleted seawater. U. rigida was initially cultivated in nitrogen-enriched seawater (daily concentrations of NH4+ and NO3- + NO2- ranged between 0.5–1.7 and 0.06–0.15 mg L-1, respectively), then transferred to nitrogen-depleted seawater where photosynthetic capacity decreased to zero after 23 d. At the time (14 d) when photosynthetic rates were lower than 2.0 μmol O2 g-1 FW min-1 and strong bleaching had occurred, some algae were returned to the initial nitrogen-enriched seawater to study recovery from N-limited growth. Data on biochemical composition (chlorophylls, ash, caloric content, fatty acids and dietary fibres) and colouration varied significantly depending on the nitrogen conditions. C:N ratios correlated significantly with biochemical parameters. Fatty acid (FA) synthesis continued during the N-starvation period; saturated and mono-unsaturated FA increased to a maximun of 72.2%, while poly-unsaturated fatty acids (PUFA) decreased to 27.7%. During the N-enriched recovery period, the reverse was found. C:N ratios above 10 correlated with carbohydrate synthesis as shown by the dietary fibre level. Under nitrogen enriched conditions, C:N ratios decreased along with a decrease in fibre level. Under controlled conditions, nitrogen represents a major influence on the development of intensive tank cultivation of Ulva rigida, not only by affecting parameters closely related to nitrogen metabolism but also some clearly influenced by carbon uptake.
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  • 67
    ISSN: 1572-9788
    Keywords: differential display ; gene expression ; hybrid vigor ; molecular marker heterozygosity ; Oryza sativa L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Using differential display analysis, we assessed the patterns of differential gene expression in hybrids relative to their parents in a diallel cross involving 8 elite rice lines. The analysis revealed several patterns of differential expression including: (1) bands present in one parent and F1 but absent in the other parent, (2) bands observed in both parents but not in the F1, (3) bands occurring in only one parent but not in the F1 or the other parent, and, (4) bands detected only in the F1 but in neither of the parents. Relationships between differential gene expression and heterosis and marker heterozygosity were evaluated using data for RFLPs, SSRs and a number of agronomic characters. The analysis showed that there was very little correlation between patterns of differential expression and the F1 means for all six agronomic traits. Differentially expressed fragments that occurred only in one parent but not in the other parent or in F1 in each of the respective crosses were positively correlated with heterosis and heterozygosity. And conversely, fragments that were detected in F1s but in neither of the respective parents were negatively correlated with heterosis and heterozygosity. The remaining patterns of differential expression were not correlated with heterosis or heterozygosity. The relationships between the patterns of differential expression and heterosis observed in this study were not consistent with expectations based on dominance or overdominance hypotheses.
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  • 68
    ISSN: 1573-0778
    Keywords: Drosophila cell culture ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract We have studied the expression of an analog of human tissue plasminogen activator, FK2P, inDrosophila Schneider 2 cells. A number of promoters were tested, including theDrosophila metallothionein promoter (MTd), baculovirus immediate early promoter (IE),Drosophila copia promoter, mouse metallothionein promoter, cytomegalovirus immediate early promoter with or without intron, SV40 immediate early promoter, and human elongation factor 1α promoter. Two of these promoters drove significant expression of FK2P. The MTd promoter is tightly regulated and upon induction with copper or cadmium expression of FK2P increases as much as 180-fold, accumulating in the culture medium to about 7 μg FK2P/106 cells/day as determined by ELISA. The IE promoter can direct the constitutive expression to yield about 0.4 μg FK2P/106 cells/day. The production of FK2P in these cell lines remains at about the same level after repeated passages, even in the absence of selective pressure. The FK2P accumulated in the culture medium is fully active in an assay using a chromogenic substrate for serine proteases. Western immunoblot analysis shows that the product remains predominately as single-chain molecules in serum-free medium, while in serum-containing medium two-chain material occurs as expected due to the presence of plasmin in serum. Judged from the size in Western immunoblots, the FK2P produced is glycosylated.
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  • 69
    ISSN: 1573-5176
    Keywords: Gelidium sesquipedale ; photosynthesis ; fluorescence ; light response curves ; pigments ; depth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photosynthesis-light response curves of Gelidium sesquipedale from the west coast of Portugal (Cape Espichel) were determined at four different depths, 3, 10, 15 and 22 m. Data acquisition using chlorophyll a fluorescence methodology and oxygen electrode measurements were compared. Response curves were determined over an increasing range of irradiance values (I), from darkness to 900 μmol photon m-2 s-1 PAR. In general, light response curves obtained for G. sesquipedale showed a similar pattern whether determined by the chlorophyll fluorescence method or by oxygen evolution. The photosynthetic capacity of G. sesquipedale decreased with depth, as expected, revealing a ‘sun’ and ‘shade’ acclimation pattern, between shallow and deeper waters.
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  • 70
    ISSN: 1573-5176
    Keywords: UV-radiation ; chlorophyll fluorescence ; photosynthesis ; stress tolerance ; electron transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photoinhibition and recovery kinetics after short exposure to solar radiation following three different irradiance treatments of irradiances (PAR, PAR+UVA and PAR+UVA+UVB) was assessed in two intertidal species of the genus Gelidium, Gelidium sesquipedale and G. latifolium, collected from Tarifa (southern Spain) using in vivo chlorophyll fluorescence (PAM fluorometry). After 3 h UV radiation exposure, optimal quantum efficiency (Fv/Fm) in G. sesquipedale decreased between 25 and 35% relative to the control. Under PAR alone, values decreased to 60%. In G. latifolium, photoinhibition did not exceed 40%. Similar results were found for the effective quantum yield (ΔF/Fm′), however, no marked differences in relation to light treatments were seen. When plants were shaded for recovery from stress, only in G. latifolium a significant increase in photosynthesis was observed (between 80 and 100% of control). In contrast, photosynthesis of G. sesquipedale suffered a chronic photoinhibition or photodamage under the three light irradiances. Full solar radiation (PAR+UVA+UVB) affected also the electron transport rate in both species. Here, initial slopes of electron transport vs. irradiance curves decreased up to 60% of controls. Although the recovery kinetic under PAR+UVA+UVB conditions was delayed in G. latifolium, after 24 h recovery this species reached significantly higher than G. sesquipedale. PAR impaired electron trasport only in G. sesquipedale. Overall, both species are characterized by different capacity to tolerate enhanced solar radiation. G. latifolium is a sun adapted plant, well suited to intertidal light conditions, whereas G. sesquipedale, growing at shaded sites in the intertidal zone, is more vulnerable to enhanced UV radiation.
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  • 71
    ISSN: 1573-5176
    Keywords: 14C ; photosynthesis ; population growth ; Selenastrum capricornutum ; suspended sediment elutriate ; zinc ; cadmium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Short-term 14C-fixation (4 h) Selenastrum capricornutum algal toxicity tests were conducted with Cd (n=8), Zn (n=9) and suspended sediment aqueous elutriates (n=28) and the results were compared to those obtained in a 48 h population growth test. In order to provide more realistic experimental conditions, toxicity tests were carried out in prefiltered nutrient-spiked Lake Geneva water. The population growth inhibition test was significantly more sensitive than the14 C-fixation test for Cd (median EC50-4h and EC50-48h values of 600 and 118 µg L-1, respectively) whereas no significant difference was measured for Zn toxicity (median EC50-4h and EC50-48h values of 97 and 96 µg L-1, respectively). With suspended sediment aqueous elutriates, the relative sensitivity of the two different end points is sample dependent, with ratios of the EC25 for the14 C-fixation: population growth test ranging from 〈0.26 to 〉53.3. Elutriate toxicity shows no apparent relationship between the acute and chronic test, indicating that population growth inhibition cannot be derived directly or predicted from14 C-fixation. Both tests with their specific advantages and limitations provide valuable complementary information to measure the impact of single toxicants or complex mixtures on aquatic plants.
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  • 72
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    Journal of applied phycology 10 (1998), S. 447-452 
    ISSN: 1573-5176
    Keywords: dense algal suspension ; light-harvesting pigment ; photosynthesis ; Synechocystis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects on photoinhibition of light-harvesting pigments in microalgal cells were examined using the wild type and a phycocyanin- deficient mutant (PD-1) of Synechosystis PCC 6714. Mutant PD-1 showed higher resistance to high light than the wild type in terms of the decline of photosynthetic activity at any light intensity and with various cell densities. This suggests that the loss of productivity induced by high light intensity would be improved by reducing the content of light-harvesting pigments.
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  • 73
    ISSN: 1573-5125
    Keywords: cryptomonads ; macromolecular ; Phototron ; photosynthesis ; UV radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We used a device called a Phototron to measure the effects of UV radiation on the cosmopolitan algae, Cryptomonas erosa, grown in continuous cultures. In the Phototron, we investigated changes in photosynthetic parameters (Pmax – specific production rate at optimal light intensity; α – initial slope of the linear portion of the Photosynthesis-Irradiance curve; and θ – the convexity or rate of bending) and carbon allocation as a function of irradiance at three different environmentally-realistic doses of UV radiation in unconditioned (no prior UV exposure) and conditioned algae (15 d previous UV exposure). For unconditioned control algae, Pmax-Total was lower, although not significantly, than the two highest UV treatments. For conditioned control algae, Pmax-Total was higher, although not significantly, than all UV treatments. Our data suggest that short term (4 h) exposure to low levels of UV (8.09 W m−2 unweighted) does not affect Pmax-Total in C. erosa, but does change the proportion of carbon allocated to lipids and proteins. Also, comparisons of lipids, polysaccharides and proteins as a percent of total carbon uptake between unconditioned and conditioned algae indicate that exposure history to UV radiation can have a negative impact on carbon allocation to lipids and proteins, in a wetland alga species that is crucial to the efficient transfer of energy through freshwater food webs.
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  • 74
    ISSN: 1573-8469
    Keywords: quorum-sensing ; gene expression ; autoinducer ; secondary metabolites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract N-acyl homoserine lactones (AHLs) function as cell density (quorum) sensing signals and regulate diverse metabolic processes in several gram negative bacteria. We report that strains of Pseudomonas syringae pvs. syringae (Pss), tabaci and tomato as well as P. corrugata and P. savastanoi produce difussible AHLs that activate the lux operons of Vibrio fischeri or the tra::lacZ fusion of Agrobacterium tumefaciens. In Pss strain B3A, AHL production occurs in cell density dependent manner. Nucleotide sequence and genetic complementation data revealed the presence of ahlIPss, a luxI homolog within the Ahl+ DNA of Pss strain B3A. The $$ahlI_{Pss}^ + $$ DNA expresses in AHL-deficient strains of P. fluorescens and E. carotovora subsp. carotovora (Ecc), and restores extracellular enzyme production and pathogenicity in the Ecc strain. The derivatives of Pss strains B3A and 301D carrying chromosomal ahlI::lacZ do not produce AHL, but like their wild type parents, produce extracellular protease and the phytotoxin syringomycin as well as elicit the hypersensitive reaction in tobacco leaves. While these strains also produce a basal level of β-galactosidase activity, the expression of ahlI::lacZ is substantially stimulated in the presence of multiple copies of the $$ahlI_{Pss}^ + $$ DNA or by the addition of cell-free spent cultures containing AHL. The activation of β-galactosidase production occurs with spent cultures of some, but not all Pseudomonas strains which produce AHL as indicated by the Lux and tra::lacZ assays. Pss strains deficient in the global regulatory genes, gacA or lemA, produce very low levels of AHL. Since inactivation of ahlIPss eliminates AHL production and since Ahl+ Pseudomonas strains carry the homolog of ahlIPss, we conclude that ahlIPss specifies a key step in AHL biosynthesis and it has been conserved in many plant pathogenic pseudomonads.
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  • 75
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    Plant molecular biology 36 (1998), S. 439-449 
    ISSN: 1573-5028
    Keywords: ethylene ; gene expression ; leaf senescence ; RNase ; tomato ; wounding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A main feature of leaf senescence is the hydrolysis of macromolecules by hydrolases of various types, and redistribution of released materials. We have initiated a study for the characterization of RNases involved in nucleic acid catabolism during senescence. Using a PCR-based cloning approach we isolated from tomato two senescence-induced RNase cDNA clones. Each of these cDNAs hybridized to a senescence-induced transcript in northern analysis. One RNase cDNA was identical to the tomato LX RNase while the second corresponded to the LE RNase. Both LX and LE RNase genes had originally been demonstrated to be induced after phosphate starvation of tomato cell culture but nothing was known about their expression or function in plants. We observed that the expression of the LX and LE genes is induced in leaves during an advanced stage of senescence with the LX transcript level being much more induced than that of LE. Low-level expression of the RNase genes was observed in flowers and artificially senescing detached leaves while no expression could be detected in stems, roots, or fruits at different ripening stages. Ethylene activated the LX gene expression in detached young leaves while LE gene expression, which could be transiently induced by wounding, appeared to be activated by abscisic acid. We suggest that the LX RNase has a role in RNA catabolism in the final stage of senescence, and LE may function during wounding as a plant defense protein.
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  • 76
    ISSN: 1573-5028
    Keywords: ferredoxin-NADP+ oxidoreductase ; petH ; divergent operator ; antisense mRNA ; phosphoribulokinase ; prk Synechocystis PCC 6803 ; photosynthesis ; cyanobacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The petH gene, encoding ferredoxin-NADP+ oxidoreductase (FNR), has been characterised in the unicellular cyanobacterium Synechocystis PCC 6803. Its product, FNR, was heterologously produced and functionally characterized. The start-site of the monocystronic petH transcript was mapped 523 bp upstream of the predicted PetH initiation codon, resulting in an unusually large 5′-untranslated region. The 5′ end of the petH transcript is situated within the open reading frame of phosphoribulokinase (encoded by prk), which is transcribed in opposite orientation with respect to petH. The transcription start site of the prk transcript was mapped 219 bp upstream of the initiation codon, resulting in a 223 bp antisense region between both transcripts. Under many conditions the expression of both genes (i.e. petH and prk) is co-regulated symmetrically at the transcriptional level, as was concluded from both northern hybridization experiments and from primer extension analyses; it became uncoupled, however, when specifically petH expression was stimulated, independent of prk expression, by stressing the Synechocystis cells with high salt concentrations. A model for a new type of bidirectional operator, regulating the expression of petH and prk, is proposed.
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  • 77
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    Plant molecular biology 36 (1998), S. 699-707 
    ISSN: 1573-5028
    Keywords: actin cytoskeleton ; in situ hybridization ; gene expression ; profilin ; RT-PCR ; tomato pollen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The actin cytoskeleton plays an important role in the growth of pollen tube. The actin-binding protein profilin could play a role in regulating the organization of the actin filaments. Using the RT-PCR technique, we isolated a cDNA clone (designated LePro1) encoding profilin from pollen grains of tomato (Lycopersicon esculentum Mill. cv. Moneymaker). Sequence analysis of the insert shows 87% similarity to tobacco ntPro2, 78% to timothy grass profilin, 77% to Arabidopsis AthPRF4, 77% to maize ZmPro3, and 73% to birch profilin. Both quantitative PCR and RNA gel blot analyses demonstrated that LePro1 is expressed in a tissue- or cell-type specific manner in the tomato plant. In situ hybridization of 2 µm thick anther sections using a non-radioactive labeling method reveals that LePro1 is expressed only in pollen grains, with undetectable transcription in other parts of the anther or other organs. Phylogenetic analysis of amino acid sequences of 18 plant profilins indicates that two distinct profilin gene classes are present in higher plants. One is pollen-specific, another is constitutive. LePro1 belongs to the former class.
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  • 78
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    Plant molecular biology 36 (1998), S. 733-739 
    ISSN: 1573-5028
    Keywords: AGAMOUS ; tomato ; ripening ; calyx ; gene expression ; sepals ; in vitro
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In vitro culture of VFNT Cherry tomato sepals (calyx) at 16–21 °C results in developmental changes that are similar to those that occur in fruit tissue [10]. Sepals become swollen, red, and succulent, produce ethylene, and have increased levels of polygalacturonase RNA. They also produce many flavor volatiles characteristic of ripe tomato fruit and undergo similar changes in sugar content [11]. We examined the expression of the tomato AGAMOUS gene, TAG1, in ripening, in vitro sepal cultures and other tissues from the plant and found that TAG1 RNA accumulates to higher levels than expected from data from other plants. Contrary to reports on the absence of AGAMOUS in sepals, TAG1 RNA levels in green sepals from greenhouse-grown plants is detectable, its concentration increasing with in vitro ripening to levels that were even higher than in red, ripe fruit. Sepals of fruit on transgenic tomato plants that expressed TAG1 ectopically were induced by low temperature to ripen in vivo, producing lycopene and undergoing cell wall softening as is characteristic of pericarpic tissue. We therefore propose that the induction of elevated TAG1 gene expression plays a key role in developmental changes that result in sepal ripening.
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  • 79
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    Plant molecular biology 37 (1998), S. 735-748 
    ISSN: 1573-5028
    Keywords: AMP-activated protein kinase ; carbohydrates ; gene expression ; gene family ; HMG-CoA reductase ; intracellular signalling ; isoprenoids ; nitrate reductase ; phosphorylation ; SNF1 ; starch ; sucrose phosphate synthase ; sucrose synthase ; sugar sensing
    Source: Springer Online Journal Archives 1860-2000
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  • 80
    ISSN: 1573-5087
    Keywords: carbohydrates ; elevated CO2 ; Gossypium hirsutum L. ; interaction ; photosynthesis ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Cotton (Gossypium hirsutum L., cv DPL 5415) plants were grown in naturally lit environment chambers at day/night temperature regimes of 26/18 (T-26/18), 31/23 (T-31/23) and 36/28 °C (T-36/28) and CO2 concentrations of 350 (C-350), 450 (C-450) and 700 μL L-1 (C-700). Net photosynthesis rates, stomatal conductance, transpiration, RuBP carboxylase activity and the foliar contents of starch and sucrose were measured during different growth stages. Net CO2 assimilation rates increased with increasing CO2 and temperature regimes. The enhancement of photosynthesis was from 24 μmol CO2 m-2 s-1 (with C-350 and T-26/18) to 41 μmol m-2 s-1 (with C-700 and T-36/28). Stomatal conductance decreased with increasing CO2 while it increased up to T-31/23 and then declined. The interactive effects of CO2 and temperature resulted in a 30% decrease in transpiration. Although the leaves grown in elevated CO2 had high starch and sucrose concentrations, their content decreased with increasing temperature. Increasing temperature from T-26/18 to 36/28 increased RuBP carboxylase activity in the order of 121, 172 and 190 μmol mg-1 chl h-1 at C-350, C-450 and C-700 respectively. Our data suggest that leaf photosynthesis in cotton benefited more from CO_2 enrichment at warm temperatures than at low growth temperature regimes.
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  • 81
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    Plant molecular biology 37 (1998), S. 1023-1033 
    ISSN: 1573-5028
    Keywords: gene expression ; psbA gene ; truncated psbA messages ; DNA-binding protein ; D1 protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Expression of the psbA genes, which in the cyanobacterium Synechococcus sp. PCC 7942 encode two different forms of the reaction centre D1 protein of photosystem II (D1:1 and D1:2), was studied under different light and temperature conditions. In addition to the mature 1200 nt psbA messages, three shorter mRNA fragments of 220, 320 and 900 nt were also found. All three mRNA fragments could be recognized by using different gene probes from the coding region of the psbAI gene, whereas the corresponding psbAII/III gene probes recognized only the 220 nt mRNA fragment. The 5' 320 nt mRNA fragment from the psbAI gene probably represents a degradation product, since the corresponding 3' 900 nt psbAI mRNA fragment was also detected. By contrast, the 5' 220 nt mRNA fragment of all psbA messages is suggested to be a truncated psbA transcript, since no corresponding 3' fragment was ever found. Inhibition of translation either by a protein synthesis inhibitor or by a shift of cells to lower temperature, increased the number of 1200 nt psbAII/III messages but the number of 5' 220 nt psbAII/III mRNA fragment increased even more dramatically. The first 66 bp after ATG, where the psbAI and psbAII/III genes mostly differ from each other, also appeared important in determining the amount of produced truncated psbA transcripts, as evidenced by the expression of different tac-psbA constructs in the presence of protein synthesis inhibitor. We suggest that both the psbAI and the psbAII/III genes have a latent intragenic termination site and truncated psbA transcripts are produced at high levels under stress conditions when transcription becomes uncoupled from translation.This is to prevent wasting metabolic energy in the production of unused transcripts.
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  • 82
    ISSN: 1573-5028
    Keywords: gene expression ; Candida albicans ; dihydrofolate reductase ; dominant selectable marker ; Nicotiana tabacum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A new binary vector encoding for Candida albicans dihydrofolate reductase (DFR1) has been constructed and used as a dominant selectable marker for plant transformation. Transgenic tobacco plants with an increased resistance to methotrexate (Mtx) were obtained by co-transformation of tobacco leaf discs with Agrobacterium tumefaciens strains carrying two new binary vectors: pTI20 and pTI18. Co-transformants of Nicotiana tabacum were directly selected for and rooted on medium containing both kanamycin (kan) and Mtx. Leaf discs of transgenic plants were assayed for capacity of regeneration at different Mtx concentrations. Analysis of transcripts was performed on total RNA extracted from two Mtx-resistant plants. The transgenic plants increased resistance to Mtx can be explained by the exceptionally low capacity of Mtx to bind C. albicans dihydrofolate reductase, accountable by the presence of two amino acid residues strategically important in Mtx binding.
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  • 83
    ISSN: 1573-5028
    Keywords: rice ; waxy ; splicing ; gene expression ; intron
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract The rice Waxy gene encodes a granule-bound starch synthase (GBSS) necessary for the synthesis of amylose in endosperm tissue. We have previously shown that a CT microsatellite near the transcriptional start site of the GBSS gene can distinguish 7 alleles that accounted for more than 80% of the variation in apparent amylose content in an extended pedigree of 89 US rice cultivars (Oryza sativa L.). Furthermore, all the cultivars with 18% or less amylose were shown to have the sequence AGTTATA at the putative leader intron 5′ splice site, while all cultivars with a higher proportion of amylose had AGGTATA. Here we demonstrate that this single-base mutation reduces the efficiency of GBSS pre-mRNA processing and results in alternate splicing at three cryptic sites. The predominant 5′ splice site in CT18 low-amylose varieties is 93 bp upstream of the splice site used in intermediate and high amylose varieties and is immediately 5′ to the CT microsatellite that we previously demonstrated to be tightly correlated with amylose content. Use of the leader intron 5′ splice site at either -93 or -1 in conjunction with the predominant 3′ splice site results in formation of a small open reading frame 38 bp upstream of the normal ATG and out of frame with it. This open reading frame is not produced when any of the 5′ leader intron splice sites are used in conjunction with an alternate 3′ splice site five bases further downstream which was observed in all rice varieties tested.
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  • 84
    ISSN: 1573-5028
    Keywords: antisense RNA ; chalcone synthase ; flavonoid ; gene expression ; rooting ; walnut
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Walnut somatic embryos (Juglans nigra × Juglans regia) were transformed with a vector containing a neomycin phosphotransferase II, a β-glucuronidase and an antisense chalcone synthase (chs) gene. This antisense construct included a 400 bp cDNA fragment of a walnut chs gene under the control of the duplicated CaMV-35S promoter. Molecular, biochemical and biological characterizations were performed both on transformed embryos propagated by secondary somatic embryogenesis and on microshoots developed by in vitro culture of embryonic epicotyls from somatic embryos. Thirteen transformed lines with the vector containing the antisense chs gene, one line with only the gus and nptII genes and one untransformed line were maintained in tissue culture. Six of the antisense lines were shown to be flavonoid-deficient. They exhibited a strongly reduced expression of chs genes, very low chalcone synthase activity and no detectable amounts of quercitrin, myricitrin, flavane-3-ols and proanthocyanidins in stems. Rooting tests showed that decreased flavonoid content in stems of antisense chs transformed lines was associated with enhanced adventitious root formation. Free auxin and conjugated auxin contents were determined during the latter phase of the micropropagation, and no variations were detected between control and antisense chs transformed lines. The in vitro plants developed a large basal callus and apical necrosis upon auxinic induction and the transformed lines highly deficient in flavonoids were more sensitive to exogenous application of indolebutyric acid (IBA).
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  • 85
    ISSN: 1573-5028
    Keywords: ribonucleotide reductase ; gene expression ; cell cycle ; S-phase ; tobacco BY2 cell suspension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Eukaryotic ribonucleotide reductase (RNR), the enzyme involved in the synthesis of the deoxyribonucleotides, consists of two R1 and R2 subunits whose activities and gene expression are differentially regulated during the cell cycle and are preferentially induced at the G1/S transition. We have isolated three cDNA clones from a tobacco S phase library, two encoding the large R1 subunit, the first cloned in plants, and one encoding the small R2 subunit. From Southern blot hybridization we deduce that RNR2 is encoded by a single-copy gene whereas RNR1 is encoded by a small multigene family. The level of RNR mRNA is cell-cycle regulated showing a maximum in S phase. In mid-S phase, RNR2 transcripts show a higher maximum level than RNR1 transcripts. Analysis of the effects of various cell cycle inhibitors added to freshly subcultured stationary phase cells leads to the conclusion that RNR gene induction at the entry of the cells into the cell cycle takes place in late G1-early S phase. Addition of DNA synthesis-blocking agents to cycling cells synchronized in mid-S phase resulted in an enhancement of RNR transcript level, thus suggesting that RNR gene expression may be linked to the DNA synthesis rate by a feedback-like regulatory mechanism.
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  • 86
    ISSN: 1573-5028
    Keywords: Nicotiana tabacum ; tobacco BY-2 cells ; gene expression ; jasmonic acid ; methyl jasmonate ; ornithine decarboxylase ; polyamine ; nicotine ; SAM synthase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A cDNA of tobacco BY-2 cells corresponding to an mRNA species which was rapidly induced by methyl jasmonate (MeJA) in the presence of cycloheximide (CHX) was found to encode ornithine decarboxylase (ODC). Another cDNA from a MeJA-inducible mRNA encoded S-adenosylmethionine synthase (SAMS). Although these enzymes could be involved in the biosynthesis of polyamines, the level of putrescine, a reaction product of ODC, increased slowly and while the levels of spermidine and spermine did not change following treatment of cells with MeJA. However, N-methylputrescine, which is a precursor of pyrrolidine ring of nicotine, started to increase shortly after MeJA-treatment of cells and the production of nicotine occured thereafter. The levels of mRNA for arginine decarboxylase (ADC), an alternative enzyme for putrescine synthesis, and that for S-adenosylmethionine decarboxylase (SAMDC), required for polyamine synthesis, were not affected by MeJA. In addition to mRNAs for ODC and SAMS, mRNA for putrescine N-methyltransferase (PMT) was also induced by MeJA. Unlike the MeJA-induction of ODC mRNA, MeJA-induction of SAMS and PMT mRNAs were blocked by CHX. The level of ODC mRNA declined after 1 to 4 h following MeJA treatment, while the levels of mRNAs for SAMS and PMT continued to increase. Auxin significantly reduced the MeJA-inducible accumulation of mRNAs for ODC, SAMS and PMT. These results indicate that MeJA sequentially induces expression of a series of genes involved in nicotine biosynthesis by multiple regulatory mechanisms.p〉
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  • 87
    ISSN: 1573-5079
    Keywords: carotenoid ; chlorophyll fluorescence ; non-photochemical quenching ; pH ; photosynthesis ; zeaxanthin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The pH dependence of maximum chlorophyll fluorescence yield (Fm) was examined in spinach thylakoids in the presence of nigericin to dissipate the transthylakoid pH gradient. 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea (DCMU) was present to eliminate photochemical quenching. Thylakoids were prepared from dark adapted leaves (‘dark’ thylakoids) or preilluminated leaves (‘light’ thylakoids). In the latter there had been approximately 50% conversion of the xanthophyll violaxanthin to zeaxanthin, while no conversion had occurred in the former. In the presence of a reductant such as ascorbate, antimycin A sensitive quenching was observed (half maximal quenching at 5 μM), whose pH dependence differed between the two types of thylakoid. Preillumination of leaves resulted in more quenching at pH values where very little quenching was observed in ‘dark’ thylakoids (pH 5–7.6). This was similar to activation of high-energy-state quenching (qE) observed previously (Rees D, Young A, Noctor G, Britton G and Horton P (1989) FEBS Lett 256: 85–90). Thylakoids isolated from preilluminated DTT treated leaves, that contained no zeaxanthin, behaved like dark thylakoids. A second form of quenching was observed in the presence of ferricyanide, that could be reversed by the addition of ascorbate. This was not antimycin A sensitive and showed the same pH dependence in both types of thylakoid. The former type of quenching, but not the latter, showed similar low temperature fluorescence emission spectra to qE, and was considered to occur by the same mechanism.
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  • 88
    ISSN: 1573-5079
    Keywords: environmental stress ; Mesembryanthemum crystallinum ; phosphoribulokinase ; gene expression ; protein expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The expression of PRK (phosphoribulokinase, E.C.2.7.1.19) in ice plant (Mesembryanthemum crystallinum) during development and under environmental stress was studied. cDNA clones were isolated and full-length cDNAs were characterized. Ice plant PRK is contained in a 1520 nucleotide transcript including a 126 nucleotide leader sequence, a 175 nucleotide 3′-end and a 20–30 nucleotide polyA+-stretch. The coding region, 397 codons, specifies a protein of Mr 44 064. The mature sequence is preceded by a transit peptide of approximately 46 amino acids. The mature portion of ice plant PRK is 86.4% identical to that of spinach and, e.g., 16.2% identical to PRK from Xanthomonas flavus. Under salt stress or cold adaptation conditions, the amount of mRNA declined by a factor of approximately three within days, followed by an increase to approximately pre-stress levels. The fluctuation in mRNA amount is not reflected on the level of transcription of the gene, suggesting post-transcriptional control, nor is PRK protein amount affected significantly over the short stress period. The recovery of transcript levels for photosynthesis-related proteins after stress appears to be a general response to environmental stresses that affect water status in ice plant. We suggest that the photosynthetic machinery in this facultative halophyte is effectively buffered from damage caused by such environmental stress.
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  • 89
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    Photosynthesis research 33 (1992), S. 163-170 
    ISSN: 1573-5079
    Keywords: biosynthetic pathway ; evolution ; free energy ; photochemistry ; photosynthesis ; porphyrin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Living matter is an organized system which requires a continual flux of energy for its survival. As a working assumption, the flux of energy required for the origin of a self-duplicating cell is taken as the power required for the maintenance of a modern cell: 10 mW per g of carbon or some 105 times the output per gram of the sun. Solar photochemistry supplies the energy for the continuing evolution of life and, by continuity, for its origin. The iron oxide-sulfide photosynthetic unit proposed by S. Granick 35 years ago was meant to supply this energy. The evolution of complex organic photosensitizers is rationalized by the Granick hypothesis that biosynthetic pathways recapitulate their evolution. These concepts are discussed in the context of the evolution of photosynthetic systems and the known properties of these pigments.
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  • 90
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    Photosynthesis research 32 (1992), S. 139-146 
    ISSN: 1573-5079
    Keywords: leaf senescence ; mesophyll conductance ; Oryza sativa L. ; photosynthesis ; specific leaf weight ; stomatal conductance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The grain yield of rice (Oryza sativa L.), as well as of other cereal crops, is limited to a large extent, by the supply of photosynthates produced during grain filling period. In this study, flag leaf photosynthesis (LPS) after heading was compared among 32 cultivars bred during the past century in Japan, to determine if the improvement of LPS has occurred with the breeding advance of high yielding cultivars. Measurement of LPS was made for 5 consecutive years in the paddy field, on the flag leaf of the main stem, at heading (LPS-0), and 2 weeks (LPS-2) and 4 weeks (LPS-4) after heading. LPS decreased with advance of leaf senescence from LPS-0 to LPS-2, and then to LPS-4. However, if nitrogen was top-dressed at the heading time, high LPS-2 was maintained, particularly in the newer cultivars. A significant positive correlation between LPS and the released year of cultivar was found at LPS-2, especially in the nitrogen top-dressed plot, but not at LPS-0 or LPS-4. Cultivar difference in LPS of the senescing leaves were not stable through the different years, whereas LPS-0 was stable over years, suggesting that the LPS in the senescent leaf is susceptible to the environmental variation due to the effects on leaf senescence. Cultivar difference in LPS at any stage was closely associated with mesophyll conductance to CO2, and stomatal conductance was also associated with cultivar difference in such a high LPS as LPS-0 and nitrogen top-dressed LPS-2. Significant correlation between LPS and specific leaf weight was not observed at any stage of the flag leaf.
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  • 91
    ISSN: 1573-5079
    Keywords: chlorophyll fluorescence ; Dunaliella ; photosynthesis ; quantum efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The yield of photosynthetic O2 evolution was measured in cultures of Dunaliella C9AA over a range of light intensities, and a range of low temperatures at constant light intensity. Changes in the rate of charge separation at Photosystem I (PS I) and Photosystem II (PS II) were estimated by the parameters ΦPS I and ΦPS II . ΦPS I is calculated on the basis of the proportion of centres in the correct redox state for charge separation to occur, as measured spectrophotometrically. ΦPS II is calculated using chlorophyll fluorescence to estimate the proportion of centres in the correct redox state, and also to estimate limitations in excitation delivery to reaction centres. With both increasing light intensity and decreasing temperature it was found that O2 evolution decreased more than predicted by either ΦPS I or ΦPS II. The results are interpreted as evidence of non-assimilatory electron flow; either linear whole chain, or cyclic around each photosystem.
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  • 92
    ISSN: 1573-5028
    Keywords: apoplast ; cDNA cloning ; conifer embryogenesis ; gene expression ; germin-like proteins ; Pinus caribaea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Germin-like proteins (GLPs) ionically bound to the walls of preglobular somatic embryos of Pinus caribaea Morelet are markers of this early developmental stage. In order to reveal the physiological implications of such markers during early embryo development, we isolated a cDNA clone from somatic embryos predicted to encode a protein with sequence similarity to GLPs. PcGER1 has an open reading frame corresponding to a 220 amino acid polypeptide with a putative N-glycosylation site on Asn-69. The presence of a 24 amino acid putative signal peptide supports the hypothesis of an apoplastic location. The N-terminal 20 amino acid sequence of the predicted mature protein is identical to the amino terminal sequence of GP111, one of the extracellular pine GLPs previously identified. Southern blot hybridizations indicate that PcGER1 is probably unique in the pine genome. Transcripts homologous to PcGER1 are abundant in all embryogenic lines, absent from nonembryogenic lines, and present in quiescent zygotic embryos but not in the female gametophyte, the haploid storage tissue of conifers. Their abundance sharply decreases during germination. Isolation of gf-0.8, a genomic fragment identical to PcGER1 cDNA sequence, confirms that no introns disrupt the coding region as it has been already described for wheat gf-2.8 and gf-3.8 genomic clones. Recombinant PcGER1, produced in Escherichia coli, is recognized by antibodies raised against the GP111 N-terminal nonapeptide and the unglycosylated wheat germin monomer. The implications of GLPs in pine embryogenesis are discussed.
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  • 93
    ISSN: 1573-5036
    Keywords: biomass ; growth ; photosynthesis ; salinity ; salt-tolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The influence of NaCl salinity on growth, dry-matter production and leaf photosynthesis of seedlings of Eucalyptus camaldulensis Dehnh. and Dalbergia sissoo Roxb. was studied by imposing 4 levels (40, 80, 120 and 160 mM) of NaCl in pot culture. Salinity up to 160 mM did not affect plant survival, but did affect plant growth and dry-matter production depending upon the species and salt concentration. NaCl reduced leaf number and dry-weight of all the plant components, but increased stem dry-weight, especially in E. camaldulensis. Salinization also stimulated total dry-matter production at all the salinity levels in E. camaldulensis but only at 40 mM in D. sissoo. The two species varied in protein and chlorophyll concentration and in leaf photosynthetic rate. Protein and chlorophyll concentration of the plants fell at all the levels of NaCl, except at 40 mM, where stimulation in the photosynthetic carbon assimilation of the plants occurred. However, no distinct relationship between leaf photosynthetic rate and dry-matter production was found. The study indicated that low salt concentrations generally stimulated growth, biomass production and rate of photosynthesis in both the species, and E. camaldulensis appeared more NaCl salt-tolerant than D. sissoo.
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  • 94
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    Plant and soil 146 (1992), S. 145-151 
    ISSN: 1573-5036
    Keywords: barley ; gene expression ; ice plant ; rice ; salt stress ; tobacco ; tomato
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Soil salinity is an important agricultural problem, particularly since the majority of crop plants have low salt tolerance. The identification of genes whose expression enables plants to adapt to or tolerate salt stress is essential for breeding programs, but little is known about the genetic mechanisms for salt tolerance. Recent research demonstrates that salt stress modulates the levels of a number of gene products. Although the detection of gene products that respons specifically to salt stress is a significant finding, they must be identified, functions assigned, and their relation to salt tolerance determined. This article focuses on a few of the salt-responsive proteins and mRNAs that have been discovered and the methods employed to identify and characterize them.
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  • 95
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    Photosynthesis research 33 (1992), S. 171-176 
    ISSN: 1573-5079
    Keywords: photosynthesis ; origin of life ; clays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The origin of photosynthesis is speculated to have involved carbon dioxide and self-replicating iron-rich clays. The later evolution of photosynthesis is considered to have undergone four distinct phases: (1) The photoreduction of carbon dioxide by ferrous ion to form oxalate and formate. (2) The entry of sulfur into the evolving clay system which led to the formation of acetyl thioesters. The polymerization of the acetyl thioeters led to the formation of quinones. The formation of Fe2S2 and Fe4S4 cores appeared in this phase. (3) The ability to fix nitrogen characterized the third phase. This led to the formation of pyrrole, flavin, nicotinamide, phycobilins, porphyrins and chlorophyll. (4) Finally, phosphate entered the evolving system. The chromophores evolved from ferrous ion through the quinones, carotenoids, phycobilins to chlorophyll. This evolution of chromophores implies that photosynthesis began in the UV and evolved through the blue, yellow, orange into the red. The electron transport chain evolved from ferrous ion through the Fe2S2 and Fe4S4 cores to the hemes.
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  • 96
    ISSN: 1573-5079
    Keywords: Chlamydomonas ; convexity ; chlorophyll a fluorescence ; Photosystem II heterogeneity ; photoinhibition ; photosynthesis ; PS II repair cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of a 60 min exposure to photosynthetic photon flux densities ranging from 300 to 2200 μmol m−2s−1 on the photosynthetic light response curve and on PS II heterogeneity as reflected in chlorophyll a fluorescence were investigated using the unicellular green alga Chlamydomonas reinhardtii. It was established that exposure to high light acts at three different regulatory or inhibitory levels; 1) regulation occurs from 300 to 780 μmol m−2s−1 where total amount of PS II centers and the shape of the light response curve is not significantly changed, 2) a first photoinhibitory range above 780 up to 1600 μmol m−2s−1 where a progressive inhibition of the quantum yield and the rate of bending (convexity) of the light response curve can be related to the loss of QB-reducing centers and 3) a second photoinhibitory range above 1600 μmol m−2s−1 where the rate of light saturated photosynthesis also decreases and convexity reaches zero. This was related to a particularly large decrease in PS IIα centers and a large increase in spill-over in energy to PS I.
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  • 97
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    Photosynthesis research 34 (1992), S. 249-262 
    ISSN: 1573-5079
    Keywords: photosynthesis ; light-harvesting chlorophyll-protein complex ; spinach ; maize
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The monomeric chlorophyll-protein complexes, CP 29 and CP 26 seen in the Camm and Green (1980) and Dunahay and Staehelin (1986) green gels do not always migrate in the order of the apparent molecular weight of their apoproteins as determined by denaturing gel electrophoresis. In barley and corn they do, but in spinach they do not. In addition, in some higher plant species these chlorophyll-protein complexes comigrate on green gels causing confusion in the literature. To remedy this situation and circumvent future confusion, we propose that the CP 29 and CP 26 complexes be named according to the relative molecular weight of their apoproteins on denaturing gels. Our proposal is supported by the results obtained from four antibodies used on Western blot samples of whole thylakoids, grana membranes, and PS II preparations from different plants. The higher molecular weight proteins (proposed CP 29's) react strongly to one set of antibodies, and the lower molecular weight proteins (proposed CP 26's) react strongly to a different set. In spinach, CP 26 antibodies react also with CP 29, but the extent of the cross-reactivity depends critically on the gel electrophoresis system used. Accordingly, a lack of antibody reactivity under certain conditions may not indicate two proteins are unrelated, just simply that a particular epitope is no longer accessible following gel electrophoresis with a particular buffer system.
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  • 98
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    Photosynthesis research 34 (1992), S. 387-395 
    ISSN: 1573-5079
    Keywords: oscillations ; photosynthesis ; regulation ; phosphate ; down-stream
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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  • 99
    ISSN: 1573-5079
    Keywords: chlorophyll fluorescence ; cyclic electron transport ; photorespiration ; photosynthesis ; Photosystem II ; proton gradient
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chlorophyll fluorescence, light scattering, the electrochromic shift P515 and levels of some photosynthetic intermediates were measured in illuminated leaves. Oxygen and CO2 concentrations in the gas phase were varied in order to obtain information on control of Photosystem II activity under conditions such as produced by water stress, when stomatal closure restricts access of CO2 to the photosynthetic apparatus. Light scattering and energy-dependent fluorescence quenching indicated a high level of chloroplast energization under high intensity illumination even when linear electron transport was curtailed in CO2-free air or in 1% oxygen with 35 μll-1 CO2. Calculations of the phosphorylation potential based on measurements of phosphoglycerate, dihydroxyacetone phosphate and NADP revealed ratios of intrathylakoid to extrathylakoid proton concentrations, which were only somewhat higher in air containing 35 μl l-1 CO2 than in CO2-free air or 1% oxygen/35 μl l-1 CO2. Anaerobic conditions prevented appreciable chloroplast energization. Acceptor-limitation of electron flow resulted in a high reduction level of the electron transport chain, which is characterized by decreased oxidation of P700, not only under anaerobic conditions, but also in air, when CO2 was absent, and in 1% oxygen, when the CO2 concentration was reduced to 35 μll-1. Efficient control of electron transport was indicated by the photoaccumulation of P700 + at or close to the CO2 compensation point in air. It is proposed to require the interplay between photorespiratory and photosynthetic electron flows, electron flow to oxygen and cyclic electron flow. The field-indicating electrochromic shift (P515) measured as a rapid absorption decrease on switching the light off followed closely the extent of photoaccumulation of P700 + in the light.
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  • 100
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    Hydrobiologia 238 (1992), S. 189-196 
    ISSN: 1573-5117
    Keywords: photosynthesis ; phytoplankton ; time scales ; environmental variability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Static P(I) curves relating photosynthesis to the instantaneous light might not be adequate to describe the activity of algal cells in lakes or oceans where mixing can cause a complex pattern of light variation. In recent years experimental results have provided evidence that, subsequent to changes in light, the rate of photosynthesis may be delayed or exhibit complex temporal dynamics. The model DYPHORA (DYnamic model for the PHOtosynthetic Rate of Algae) takes these dynamics into account by introducing two characteristic response times for the biological processes: (1) the effect of light inhibition having a time scale of minutes to a few hours and (2) the time lag of the rate of photosynthesis for increasing light intensities having a time scale of seconds to minutes. The importance of the dynamic relative to the static description of photosynthesis depends on the time scales of the changes in the environment and the biological response, becoming significant when the time scales are comparable.
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