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  • 1
    Online-Ressource
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    Deficiency of mitochondrial fumarase activity in tomato plants impairs photosynthesis via an effect on stomatal function
    Wiley ; 2007
    In:  The Plant Journal Vol. 50, No. 6 ( 2007-06), p. 1093-1106
    Details
    In: The Plant Journal, Wiley, Vol. 50, No. 6 ( 2007-06), p. 1093-1106
    Kurzfassung: Transgenic tomato ( Solanum lycopersicum ) plants expressing a fragment of a fumarate hydratase (fumarase) gene in the antisense orientation and exhibiting considerable reductions in the mitochondrial activity of this enzyme show impaired photosynthesis. The rate of the tricarboxylic acid cycle was reduced in the transformants relative to the other major pathways of carbohydrate oxidation and the plants were characterized by a restricted rate of dark respiration. However, biochemical analyses revealed relatively little alteration in leaf metabolism as a consequence of reducing the fumarase activity. That said, in comparison to wild‐type plants, CO 2 assimilation was reduced by up to 50% under atmospheric conditions and plants were characterized by a reduced biomass on a whole plant basis. Analysis of further photosynthetic parameters revealed that there was little difference in pigment content in the transformants but that the rate of transpiration and stomatal conductance was markedly reduced. Analysis of the response of the rate of photosynthesis to variation in the concentration of CO 2 confirmed that this restriction was due to a deficiency in stomatal function.
    Materialart: Online-Ressource
    ISSN: 0960-7412 , 1365-313X
    URL: Issue
    URL: Article
    DOI: 10.1111/tpj.2007.50.issue-6
    DOI: 10.1111/j.1365-313X.2007.03115.x
    Sprache: Englisch
    Verlag: Wiley
    Publikationsdatum: 2007
    ZDB Id: 2020961-7
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
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    Decrease in Manganese Superoxide Dismutase Leads to Reduced Root Growth and Affects Tricarboxylic Acid Cycle Flux and Mitochondrial Redox Homeostasis    
    Oxford University Press (OUP) ; 2008
    In:  Plant Physiology Vol. 147, No. 1 ( 2008-04-28), p. 101-114
    Details
    In: Plant Physiology, Oxford University Press (OUP), Vol. 147, No. 1 ( 2008-04-28), p. 101-114
    Kurzfassung: Superoxide dismutases (SODs) are key components of the plant antioxidant defense system. While plastidic and cytosolic isoforms have been extensively studied, the importance of mitochondrial SOD at a cellular and whole-plant level has not been established. To address this, transgenic Arabidopsis (Arabidopsis thaliana) plants were generated in which expression of AtMSD1, encoding the mitochondrial manganese (Mn)SOD, was suppressed by antisense. The strongest antisense line showed retarded root growth even under control growth conditions. There was evidence for a specific disturbance of mitochondrial redox homeostasis in seedlings grown in liquid culture: a mitochondrially targeted redox-sensitive green fluorescent protein was significantly more oxidized in the MnSOD-antisense background. In contrast, there was no substantial change in oxidation of cytosolically targeted redox-sensitive green fluorescent protein, nor changes in antioxidant defense components. The consequences of altered mitochondrial redox status of seedlings were subtle with no widespread increase of mitochondrial protein carbonyls or inhibition of mitochondrial respiratory complexes. However, there were specific inhibitions of tricarboxylic acid (TCA) cycle enzymes (aconitase and isocitrate dehydrogenase) and an inhibition of TCA cycle flux in isolated mitochondria. Nevertheless, total respiratory CO2 output of seedlings was not decreased, suggesting that the inhibited TCA cycle enzymes can be bypassed. In older, soil-grown plants, redox perturbation was more pronounced with changes in the amount and/or redox poise of ascorbate and glutathione. Overall, the results demonstrate that reduced MnSOD affects mitochondrial redox balance and plant growth. The data also highlight the flexibility of plant metabolism with TCA cycle inhibition having little effect on overall respiratory rates.
    Materialart: Online-Ressource
    ISSN: 1532-2548
    URL: Article
    DOI: 10.1104/pp.107.113613
    Sprache: Englisch
    Verlag: Oxford University Press (OUP)
    Publikationsdatum: 2008
    ZDB Id: 2004346-6
    ZDB Id: 208914-2
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
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    The Metabolic Response of Heterotrophic Arabidopsis Cells to Oxidative Stress
    Oxford University Press (OUP) ; 2007
    In:  Plant Physiology Vol. 143, No. 1 ( 2007-01-08), p. 312-325
    Details
    In: Plant Physiology, Oxford University Press (OUP), Vol. 143, No. 1 ( 2007-01-08), p. 312-325
    Kurzfassung: To cope with oxidative stress, the metabolic network of plant cells must be reconfigured either to bypass damaged enzymes or to support adaptive responses. To characterize the dynamics of metabolic change during oxidative stress, heterotrophic Arabidopsis (Arabidopsis thaliana) cells were treated with menadione and changes in metabolite abundance and 13C-labeling kinetics were quantified in a time series of samples taken over a 6 h period. Oxidative stress had a profound effect on the central metabolic pathways with extensive metabolic inhibition radiating from the tricarboxylic acid cycle and including large sectors of amino acid metabolism. Sequential accumulation of metabolites in specific pathways indicated a subsequent backing up of glycolysis and a diversion of carbon into the oxidative pentose phosphate pathway. Microarray analysis revealed a coordinated transcriptomic response that represents an emergency coping strategy allowing the cell to survive the metabolic hiatus. Rather than attempt to replace inhibited enzymes, transcripts encoding these enzymes are in fact down-regulated while an antioxidant defense response is mounted. In addition, a major switch from anabolic to catabolic metabolism is signaled. Metabolism is also reconfigured to bypass damaged steps (e.g. induction of an external NADH dehydrogenase of the mitochondrial respiratory chain). The overall metabolic response of Arabidopsis cells to oxidative stress is remarkably similar to the superoxide and hydrogen peroxide stimulons of bacteria and yeast (Saccharomyces cerevisiae), suggesting that the stress regulatory and signaling pathways of plants and microbes may share common elements.
    Materialart: Online-Ressource
    ISSN: 1532-2548
    URL: Article
    DOI: 10.1104/pp.106.090431
    Sprache: Englisch
    Verlag: Oxford University Press (OUP)
    Publikationsdatum: 2007
    ZDB Id: 2004346-6
    ZDB Id: 208914-2
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
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    ADP-Glucose Pyrophosphorylase-Deficient Pea Embryos Reveal Specific Transcriptional and Metabolic Changes of Carbon-Nitrogen Metabolism and Stress Responses  
    Oxford University Press (OUP) ; 2009
    In:  Plant Physiology Vol. 149, No. 1 ( 2009-01-06), p. 395-411
    Details
    In: Plant Physiology, Oxford University Press (OUP), Vol. 149, No. 1 ( 2009-01-06), p. 395-411
    Kurzfassung: We present a comprehensive analysis of ADP-glucose pyrophosphorylase (AGP)-repressed pea (Pisum sativum) seeds using transcript and metabolite profiling to monitor the effects that reduced carbon flow into starch has on carbon-nitrogen metabolism and related pathways. Changed patterns of transcripts and metabolites suggest that AGP repression causes sugar accumulation and stimulates carbohydrate oxidation via glycolysis, tricarboxylic acid cycle, and mitochondrial respiration. Enhanced provision of precursors such as acetyl-coenzyme A and organic acids apparently support other pathways and activate amino acid and storage protein biosynthesis as well as pathways fed by cytosolic acetyl-coenzyme A, such as cysteine biosynthesis and fatty acid elongation/metabolism. As a consequence, the resulting higher nitrogen (N) demand depletes transient N storage pools, specifically asparagine and arginine, and leads to N limitation. Moreover, increased sugar accumulation appears to stimulate cytokinin-mediated cell proliferation pathways. In addition, the deregulation of starch biosynthesis resulted in indirect changes, such as increased mitochondrial metabolism and osmotic stress. The combined effect of these changes is an enhanced generation of reactive oxygen species coupled with an up-regulation of energy-dissipating, reactive oxygen species protection, and defense genes. Transcriptional activation of mitogen-activated protein kinase pathways and oxylipin synthesis indicates an additional activation of stress signaling pathways. AGP-repressed embryos contain higher levels of jasmonate derivatives; however, this increase is preferentially in nonactive forms. The results suggest that, although metabolic/osmotic alterations in iAGP pea seeds result in multiple stress responses, pea seeds have effective mechanisms to circumvent stress signaling under conditions in which excessive stress responses and/or cellular damage could prematurely initiate senescence or apoptosis.
    Materialart: Online-Ressource
    ISSN: 1532-2548
    URL: Article
    DOI: 10.1104/pp.108.129940
    Sprache: Englisch
    Verlag: Oxford University Press (OUP)
    Publikationsdatum: 2009
    ZDB Id: 2004346-6
    ZDB Id: 208914-2
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 5
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    The 2-oxoglutarate/malate translocator mediates amino acid and storage protein biosynthesis in pea embryos : OMT controls amino acid biosynthesis in seeds
    Wiley ; 2009
    In:  The Plant Journal Vol. 61, No. 2 ( 2009-11-18), p. 350-363
    Details
    In: The Plant Journal, Wiley, Vol. 61, No. 2 ( 2009-11-18), p. 350-363
    Materialart: Online-Ressource
    ISSN: 0960-7412
    URL: Article
    DOI: 10.1111/j.1365-313X.2009.04058.x
    Sprache: Englisch
    Verlag: Wiley
    Publikationsdatum: 2009
    ZDB Id: 2020961-7
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 6
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    The Critical Role of Arabidopsis Electron-Transfer Flavoprotein:Ubiquinone Oxidoreductase during Dark-Induced Starvation
    Oxford University Press (OUP) ; 2005
    In:  The Plant Cell Vol. 17, No. 9 ( 2005-09-01), p. 2587-2600
    Details
    In: The Plant Cell, Oxford University Press (OUP), Vol. 17, No. 9 ( 2005-09-01), p. 2587-2600
    Kurzfassung: In mammals, electron-transfer flavoprotein:ubiquinone oxidoreductase (ETFQO) and electron-transfer flavoprotein (ETF) are functionally associated, and ETF accepts electrons from at least nine mitochondrial matrix flavoprotein dehydrogenases and transfers them to ubiquinone in the inner mitochondrial membrane. In addition, the mammalian ETF/ETFQO system plays a key role in β-oxidation of fatty acids and catabolism of amino acids and choline. By contrast, nothing is known of the function of ETF and ETFQO in plants. Sequence analysis of the unique Arabidopsis thaliana homologue of ETFQO revealed high similarity to the mammalian ETFQO protein. Moreover, green fluorescent protein cellular localization experiments suggested a mitochondrial location for this protein. RNA gel blot analysis revealed that Arabidopsis ETFQO transcripts accumulated in long-term dark-treated leaves. Analysis of three independent insertional mutants of Arabidopsis ETFQO revealed a dramatic reduction in their ability to withstand extended darkness, resulting in senescence and death within 10 d after transfer, whereas wild-type plants remained viable for at least 15 d. Metabolite profiling of dark-treated leaves of the wild type and mutants revealed a dramatic decline in sugar levels. In contrast with the wild type, the mutants demonstrated a significant accumulation of several amino acids, an intermediate of Leu catabolism, and, strikingly, high-level accumulation of phytanoyl-CoA. These data demonstrate the involvement of a mitochondrial protein, ETFQO, in the catabolism of Leu and potentially of other amino acids in higher plants and also imply a novel role for this protein in the chlorophyll degradation pathway activated during dark-induced senescence and sugar starvation.
    Materialart: Online-Ressource
    ISSN: 1532-298X
    URL: Article
    DOI: 10.1105/tpc.105.035162
    Sprache: Englisch
    Verlag: Oxford University Press (OUP)
    Publikationsdatum: 2005
    ZDB Id: 623171-8
    ZDB Id: 2004373-9
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 7
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    Enhanced Photosynthetic Performance and Growth as a Consequence of Decreasing Mitochondrial Malate Dehydrogenase Activity in Transgenic Tomato Plants
    Oxford University Press (OUP) ; 2005
    In:  Plant Physiology Vol. 137, No. 2 ( 2005-02-01), p. 611-622
    Details
    In: Plant Physiology, Oxford University Press (OUP), Vol. 137, No. 2 ( 2005-02-01), p. 611-622
    Kurzfassung: Transgenic tomato (Solanum lycopersicum) plants expressing a fragment of the mitochondrial malate dehydrogenase gene in the antisense orientation and exhibiting reduced activity of this isoform of malate dehydrogenase show enhanced photosynthetic activity and aerial growth under atmospheric conditions (360 ppm CO2). In comparison to wild-type plants, carbon dioxide assimilation rates and total plant dry matter were up to 11% and 19% enhanced in the transgenics, when assessed on a whole-plant basis. Accumulation of carbohydrates and redox-related compounds such as ascorbate was also markedly elevated in the transgenics. Also increased in the transgenic plants was the capacity to use l-galactono-lactone, the terminal precursor of ascorbate biosynthesis, as a respiratory substrate. Experiments in which ascorbate was fed to isolated leaf discs also resulted in increased rates of photosynthesis providing strong indication for an ascorbate-mediated link between the energy-generating processes of respiration and photosynthesis. This report thus shows that the repression of this mitochondrially localized enzyme improves both carbon assimilation and aerial growth in a crop species.
    Materialart: Online-Ressource
    ISSN: 1532-2548 , 0032-0889
    URL: Article
    DOI: 10.1104/pp.104.055566
    RVK:
    WA 15000
    Sprache: Englisch
    Verlag: Oxford University Press (OUP)
    Publikationsdatum: 2005
    ZDB Id: 2004346-6
    ZDB Id: 208914-2
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 8
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    Glycolytic Enzymes Associate Dynamically with Mitochondria in Response to Respiratory Demand and Support Substrate Channeling
    Oxford University Press (OUP) ; 2007
    In:  The Plant Cell Vol. 19, No. 11 ( 2007-12-31), p. 3723-3738
    Details
    In: The Plant Cell, Oxford University Press (OUP), Vol. 19, No. 11 ( 2007-12-31), p. 3723-3738
    Kurzfassung: In Arabidopsis thaliana, enzymes of glycolysis are present on the surface of mitochondria and free in the cytosol. The functional significance of this dual localization has now been established by demonstrating that the extent of mitochondrial association is dependent on respiration rate in both Arabidopsis cells and potato (Solanum tuberosum) tubers. Thus, inhibition of respiration with KCN led to a proportional decrease in the degree of association, whereas stimulation of respiration by uncoupling, tissue ageing, or overexpression of invertase led to increased mitochondrial association. In all treatments, the total activity of the glycolytic enzymes in the cell was unaltered, indicating that the existing pools of each enzyme repartitioned between the cytosol and the mitochondria. Isotope dilution experiments on isolated mitochondria, using 13C nuclear magnetic resonance spectroscopy to monitor the impact of unlabeled glycolytic intermediates on the production of downstream intermediates derived from 13C-labeled precursors, provided direct evidence for the occurrence of variable levels of substrate channeling. Pull-down experiments suggest that interaction with the outer mitochondrial membrane protein, VDAC, anchors glycolytic enzymes to the mitochondrial surface. It appears that glycolytic enzymes associate dynamically with mitochondria to support respiration and that substrate channeling restricts the use of intermediates by competing metabolic pathways.
    Materialart: Online-Ressource
    ISSN: 1532-298X
    URL: Article
    DOI: 10.1105/tpc.107.053371
    Sprache: Englisch
    Verlag: Oxford University Press (OUP)
    Publikationsdatum: 2007
    ZDB Id: 623171-8
    ZDB Id: 2004373-9
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 9
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    The mitochondrial electron transfer flavoprotein complex is essential for survival of Arabidopsis in extended darkness
    Wiley ; 2006
    In:  The Plant Journal Vol. 47, No. 5 ( 2006-09), p. 751-760
    Details
    In: The Plant Journal, Wiley, Vol. 47, No. 5 ( 2006-09), p. 751-760
    Kurzfassung: In mammals, the electron transfer flavoprotein (ETF) is a heterodimeric protein composed of two subunits, α and β , that is responsible for the oxidation of at least nine mitochondrial matrix flavoprotein dehydrogenases. Electrons accepted by ETF are further transferred to the main respiratory chain via the ETF ubiquinone oxide reductase (ETFQO). Sequence analysis of the unique Arabidopsis homologues of two subunits of ETF revealed their high similarity to both subunits of the mammalian ETF. Yeast two‐hybrid experiments showed that the Arabidopsis ETF α and ETF β can form a heteromeric protein. Isolation and characterization of two independent T‐DNA insertional Arabidopsis mutants of the ETF β gene revealed accelerated senescence and early death compared to wild‐type during extended darkness. Furthermore in contrast to wild‐type, the etfb mutants demonstrated a significant accumulation of several amino acids, isovaleryl CoA and phytanoyl CoA during dark‐induced carbohydrate deprivation. These phenotypic characteristics of etfb mutants are broadly similar to those that we observed previously in Arabidopsis etfqo mutants, suggesting functional association between ETF and ETFQO in Arabidopsis, and confirming the essential roles of the ETF/ETFQO electron transfer complex in the catabolism of leucine and involvement in the chlorophyll degradation pathway activated during dark‐induced carbohydrate deprivation.
    Materialart: Online-Ressource
    ISSN: 0960-7412 , 1365-313X
    URL: Issue
    URL: Article
    DOI: 10.1111/tpj.2006.47.issue-5
    DOI: 10.1111/j.1365-313X.2006.02826.x
    Sprache: Englisch
    Verlag: Wiley
    Publikationsdatum: 2006
    ZDB Id: 2020961-7
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 10
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    RNA interference‐mediated repression of sucrose‐phosphatase in transgenic potato tubers ( Solanum tuberosum ) strongly affects the hexose‐to‐sucrose ratio upon cold storage with only minor effects on total soluble carbohydrate accumulation
    Wiley ; 2008
    In:  Plant, Cell & Environment Vol. 31, No. 1 ( 2008-01), p. 165-176
    Details
    In: Plant, Cell & Environment, Wiley, Vol. 31, No. 1 ( 2008-01), p. 165-176
    Kurzfassung: Storage of potato tubers at low temperatures leads to the accumulation of glucose and fructose in a process called ‘cold sweetening’. The aim of this work was to investigate the role of sucrose‐phosphatase (SPP) in potato tuber carbohydrate metabolism at low temperature (4 °C). To this end, RNA interference (RNAi) was used to reduce SPP expression in transgenic potato tubers. Analysis of SPP specific small interfering RNAs (siRNAs), SPP protein accumulation and enzyme activity indicated that SPP silencing in transgenic tubers was stable during the cold treatment. Analysis of soluble carbohydrates showed that in transgenic tubers, cold‐induced hexogenesis was inhibited while, despite strongly reduced SPP activity, sucrose levels exceeded wild‐type (WT) values four‐ to fivefold after 34 d of cold treatment. This led to a drastic change in the hexose‐to‐sucrose ratio from 1.9 in WT tubers to 0.15 to 0.11 in transgenic tubers, while the total amount of soluble sugars was largely unchanged in both genotypes. Sucrose‐6 F ‐phosphate (Suc6P), the substrate of SPP, accumulated in transgenic tubers in the cold which most likely enables the residual enzyme to operate with maximal catalytic activity in vivo and thus, in the long term, counterbalances reduced SPP activity in the transformants. Northern analysis revealed that cold‐induced expression of vacuolar invertase (VI) was blocked in SPP‐silenced tubers explaining a reduced sucrose‐to‐hexose conversion. Suc6P levels were found to negatively correlate with VI expression. A possible role of Suc6P in regulating VI expression is discussed.
    Materialart: Online-Ressource
    ISSN: 0140-7791 , 1365-3040
    URL: Issue
    URL: Article
    DOI: 10.1111/pce.2008.31.issue-1
    DOI: 10.1111/j.1365-3040.2007.01747.x
    RVK:
    WA 15000
    Sprache: Englisch
    Verlag: Wiley
    Publikationsdatum: 2008
    ZDB Id: 391893-2
    ZDB Id: 2020843-1
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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