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Vers une meilleure compréhension des systèmes antioxydants chez la plante face aux contraintes environnementales : approches expérimentales et modélisation mécaniste

Abstract : The most important metabolic pathways in the control of oxidative stress remain to be elucidated in plants. Those linked to glutathione play an important role. However, the reactions responsible for its oxidation have not been clearly identified. Here, analysis based on available biochemical, transcriptomic and genetic data emphasized likely important questions to be elucidated for a full understanding of how stress-related redox regulation might impinge on phytohormone-related signaling pathways. Using a reverse genetics approach and the photorespiratory conditional cat2 mutant, we studied the response and functional importance of three potential routes for glutathione oxidation pathways mediated by glutathione S-transferases, glutaredoxin dependent peroxiredoxins, and dehydroascorbate reductases (DHAR) in Arabidopsis during oxidative stress. Hence, interplay between different DHARs appears to be necessary to couple ascorbate and glutathione pools and to allow glutathione-related signaling during enhanced H2O2 metabolism. In addition to experimental work, modelling is another way to investigate H2O2 production and its metabolism related to catalase activity and ascorbate glutathione pathway. This approach led to major conclusions, that catalase and ascorbate peroxidase can share the load in H2O2 processing even in optimal growth conditions. Furthermore, simulations propose that NADPH availability may determine glutathione oxidation through its influence on monodehydroascorbate reduction. Taken together, experimental results and our kinetic model strengthen that the sensitivity of glutathione status to oxidative stress acts as a suitable sensor of increased H2O2.
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Marie Sylviane Rahantaniaina. Vers une meilleure compréhension des systèmes antioxydants chez la plante face aux contraintes environnementales : approches expérimentales et modélisation mécaniste. Biologie végétale. Sorbonne Université, 2018. Français. ⟨NNT : 2018SORUS246⟩. ⟨tel-02372940⟩

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