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Décryptage des cascades de signalisation liées au stress par phosphoprotéomique et génétique fonctionnelle chez Botrytis cinerea

Abstract : Perception and adaptation to the environment are essential processes for the survival of living organisms. The phytopathogenic fungus Botrytis cinerea can thus perceive different types of signals, whether they are chemical or physical. The signalling pathway of the Sak1 MAPK is involved in the adaptation to osmotic, oxidative and cell wall stress, but also in sporulation and pathogenicity by regulating plant penetration and necrosis development. In order to deepen existing knowledge of the Sak1 pathway, we have carried out global studies based on proteomics and phosphoproteomics techniques. A comparative proteomics analysis between the wild type and the signalling mutants ∆bos1 and ∆sak1 showed, among others, that Sak1 regulates the abundance of proteins involved in the G-protein pathway and calcium pathway. This connection with G-proteins was confirmed by a decrease in cAMP concentration in the ∆sak1 mutant. Using fludioxonil as signal for the activation of Sak1 for a phosphoproteomic analysis revealed changes in the state of protein phosphorylation. Among these differentially phosphorylated proteins, the presence of PKAR (regulatory subunit of protein kinase A) and the transcription factor CRZ1, indicates an action on the G-protein and calcium pathway respectively, validating the results obtained by proteomics. Phosphoproteomics revealed a phosducin-like protein, PhnA. Its functional characterization reveals its role in stress adaptation, sporulation and germination, as well as in pathogenicity, thus demonstrating a new pathogenicity factor in B. cinerea. Our study revealed interactions between Sak1 and other unsuspected signalling pathways, affecting both the production of certain components (transcriptional and translational regulations) and phosphorylation (post-translational modifications). Our results will create the basis for new research questions to complement our understanding of these interactions involving adaptation to stress and pathogenesis of B. cinerea.
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Jaafar Kilani. Décryptage des cascades de signalisation liées au stress par phosphoprotéomique et génétique fonctionnelle chez Botrytis cinerea. Biologie moléculaire. Université Paris Saclay (COmUE), 2018. Français. ⟨NNT : 2018SACLS050⟩. ⟨tel-01865827⟩

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