The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
Gert Schansker - One of the best experts on this subject based on the ideXlab platform.
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Salt stress effects on the photosynthetic Electron Transport Chain in two chickpea lines differing in their salt stress tolerance
Photosynthesis Research, 2018Co-Authors: Nuran Çiçek, Abdallah Oukarroum, Reto J. Strasser, Gert SchanskerAbstract:The main objective of this study was to evaluate the effects of salt stress on the photosynthetic Electron Transport Chain using two chickpea lines ( Cicer arietinum L.) differing in their salt stress tolerance at the germination stage (AKN 87 and AKN 290). Two weeks after sowing, seedlings were exposed to salt stress for 2 weeks and irrigated with 200 ml of 200 mM NaCl every 2 days. The polyphasic OJIP fluorescence transient and the 820-nm transmission kinetics (photosystem I) were used to evaluate the effects of salt stress on the functionality of the photosynthetic Electron Transport Chain. It was observed that a signature for salt stress was a combination of a higher J step (V_J), a smaller IP amplitude, and little or no effect on the primary quantum yield of PSII (φ_Po). We observed for AKN 290 a shorter leaf life cycle, which may represent a mechanism to cope with salt stress. For severely salt-stressed leaves, an inhibition of Electron flow between the PQ pool and P700 was found. The data also suggest that the properties of Electron flow beyond PSI are affected by salt stress.
Martin D Brand - One of the best experts on this subject based on the ideXlab platform.
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Topology of superoxide production from different sites in the mitochondrial Electron Transport Chain
Journal of Biological Chemistry, 2002Co-Authors: Julie St-pierre, Stephen J. Roebuck, Julie A Buckingham, Martin D BrandAbstract:We measured production of reactive oxygen species by intact mitochondria from rat skeletal muscle, heart, and liver under various experimental conditions. By using different substrates and inhibitors, we determined the sites of production (which complexes in the Electron Transport Chain produced superoxide). By measuring hydrogen peroxide production in the absence and presence of exogenous superoxide dismutase, we established the topology of superoxide production (on which side of the mitochondrial inner membrane superoxide was produced). Mitochondria did not release measurable amounts of superoxide or hydrogen peroxide when respiring on complex I or complex II substrates. Mitochondria from skeletal muscle or heart generated significant amounts of superoxide from complex I when respiring on palmitoyl carnitine. They produced superoxide at considerable rates in the presence of various inhibitors of the Electron Transport Chain. Complex I (and perhaps the fatty acid oxidation Electron transfer flavoprotein and its oxidoreductase) released superoxide on the matrix side of the inner membrane, whereas center o of complex III released superoxide on the cytoplasmic side. These results do not support the idea that mitochondria produce considerable amounts of reactive oxygen species under physiological conditions. Our upper estimate of the proportion of Electron flow giving rise to hydrogen peroxide with palmitoyl carnitine as substrate (0.15%) is more than an order of magnitude lower than commonly cited values. We observed no difference in the rate of hydrogen peroxide production between rat and pigeon heart mitochondria respiring on complex I substrates. However, when complex I was fully reduced using rotenone, rat mitochondria released significantly more hydrogen peroxide than pigeon mitochondria. This difference was solely due to an elevated concentration of complex I in rat compared with pigeon heart mitochondria.
Nuran Çiçek - One of the best experts on this subject based on the ideXlab platform.
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Salt stress effects on the photosynthetic Electron Transport Chain in two chickpea lines differing in their salt stress tolerance
Photosynthesis Research, 2018Co-Authors: Nuran Çiçek, Abdallah Oukarroum, Reto J. Strasser, Gert SchanskerAbstract:The main objective of this study was to evaluate the effects of salt stress on the photosynthetic Electron Transport Chain using two chickpea lines ( Cicer arietinum L.) differing in their salt stress tolerance at the germination stage (AKN 87 and AKN 290). Two weeks after sowing, seedlings were exposed to salt stress for 2 weeks and irrigated with 200 ml of 200 mM NaCl every 2 days. The polyphasic OJIP fluorescence transient and the 820-nm transmission kinetics (photosystem I) were used to evaluate the effects of salt stress on the functionality of the photosynthetic Electron Transport Chain. It was observed that a signature for salt stress was a combination of a higher J step (V_J), a smaller IP amplitude, and little or no effect on the primary quantum yield of PSII (φ_Po). We observed for AKN 290 a shorter leaf life cycle, which may represent a mechanism to cope with salt stress. For severely salt-stressed leaves, an inhibition of Electron flow between the PQ pool and P700 was found. The data also suggest that the properties of Electron flow beyond PSI are affected by salt stress.
Julie St-pierre - One of the best experts on this subject based on the ideXlab platform.
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Impact of PGC-1α on the topology and rate of superoxide production by the mitochondrial Electron Transport Chain.
Free Radical Biology and Medicine, 2011Co-Authors: Shane Austin, Eva Klimcakova, Julie St-pierreAbstract:Abstract Reactive oxygen species (ROS) play an important role in normal signaling events and excessive ROS are associated with many pathological conditions. The amount of ROS in cells is dependent on both the production of ROS by the mitochondrial Electron Transport Chain and their removal by ROS-detoxifying enzymes. The peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) is a master regulator of mitochondrial functions and a key regulator of the ROS-detoxifying program. However, the impact of PGC-1α on the topology and rate of superoxide production by the mitochondrial Electron Transport Chain is not known. We report here, using mitochondria from muscle creatine kinase–PGC-1α transgenic mice, that PGC-1α does not affect the topology of ROS production, but increases the capacity of complexes I and III to generate ROS. These changes are associated with increased mitochondrial respiration and content of respiratory Chain complexes. When normalizing ROS production to mitochondrial respiration, we find that PGC-1α preserves the percentage of free radical leak by the Electron Transport Chain. Together, these data demonstrate that PGC-1α regulates the intrinsic properties of mitochondria in such a way as to preserve a tight coupling between mitochondrial respiration and ROS production.
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Topology of superoxide production from different sites in the mitochondrial Electron Transport Chain
Journal of Biological Chemistry, 2002Co-Authors: Julie St-pierre, Stephen J. Roebuck, Julie A Buckingham, Martin D BrandAbstract:We measured production of reactive oxygen species by intact mitochondria from rat skeletal muscle, heart, and liver under various experimental conditions. By using different substrates and inhibitors, we determined the sites of production (which complexes in the Electron Transport Chain produced superoxide). By measuring hydrogen peroxide production in the absence and presence of exogenous superoxide dismutase, we established the topology of superoxide production (on which side of the mitochondrial inner membrane superoxide was produced). Mitochondria did not release measurable amounts of superoxide or hydrogen peroxide when respiring on complex I or complex II substrates. Mitochondria from skeletal muscle or heart generated significant amounts of superoxide from complex I when respiring on palmitoyl carnitine. They produced superoxide at considerable rates in the presence of various inhibitors of the Electron Transport Chain. Complex I (and perhaps the fatty acid oxidation Electron transfer flavoprotein and its oxidoreductase) released superoxide on the matrix side of the inner membrane, whereas center o of complex III released superoxide on the cytoplasmic side. These results do not support the idea that mitochondria produce considerable amounts of reactive oxygen species under physiological conditions. Our upper estimate of the proportion of Electron flow giving rise to hydrogen peroxide with palmitoyl carnitine as substrate (0.15%) is more than an order of magnitude lower than commonly cited values. We observed no difference in the rate of hydrogen peroxide production between rat and pigeon heart mitochondria respiring on complex I substrates. However, when complex I was fully reduced using rotenone, rat mitochondria released significantly more hydrogen peroxide than pigeon mitochondria. This difference was solely due to an elevated concentration of complex I in rat compared with pigeon heart mitochondria.
Navdeep S. Chandel - One of the best experts on this subject based on the ideXlab platform.
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Genetics of mitochondrial Electron Transport Chain in regulating oxygen sensing.
Methods in Enzymology, 2007Co-Authors: Eric L. Bell, Navdeep S. ChandelAbstract:Oxygen is the terminal Electron acceptor in the mitochondrial Electron Transport Chain and therefore is required for the generation of energy through oxidative phosphorylation. In environments of decreased oxygen levels (hypoxia), organisms have developed an adaptive response through the activation of the hypoxia-inducible transcription factor (HIF) to maintain their energetic demand. In order to sense hypoxic environments, cells have developed oxygen-sensing machinery that allows for the activation of HIF. The mitochondrial Electron Transport Chain is required for the oxygen-sensing pathway. This chapter outlines methods used to explore the role of the Electron Transport Chain and a by-product of Electron Transport, reactive oxygen species, in oxygen sensing.
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bcl 2 family members and functional Electron Transport Chain regulate oxygen deprivation induced cell death
Molecular and Cellular Biology, 2002Co-Authors: David S Mcclintock, Matthew T Santore, Vivian Y Lee, Joslyn K Brunelle, G Scott R Budinger, Weixing Zong, Craig B Thompson, Nissim Hay, Navdeep S. ChandelAbstract:The mechanisms underlying cell death during oxygen deprivation are unknown. We report here a model for oxygen deprivation-induced apoptosis. The death observed during oxygen deprivation involves a decrease in the mitochondrial membrane potential, followed by the release of cytochrome c and the activation of caspase-9. Bcl-XL prevented oxygen deprivation-induced cell death by inhibiting the release of cytochrome c and caspase-9 activation. The ability of Bcl-XL to prevent cell death was dependent on allowing the import of glycolytic ATP into the mitochondria to generate an inner mitochondrial membrane potential through the F1F0-ATP synthase. In contrast, although activated Akt has been shown to inhibit apoptosis induced by a variety of apoptotic stimuli, it did not prevent cell death during oxygen deprivation. In addition to Bcl-XL, cells devoid of mitochondrial DNA (ρ° cells) that lack a functional Electron Transport Chain were resistant to oxygen deprivation. Further, murine embryonic fibroblasts from bax−/− bak−/− mice did not die in response to oxygen deprivation. These data suggest that when subjected to oxygen deprivation, cells die as a result of an inability to maintain a mitochondrial membrane potential through the import of glycolytic ATP. Proapoptotic Bcl-2 family members and a functional Electron Transport Chain are required to initiate cell death in response to oxygen deprivation.