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Caractérisation des mécanismes régulant les modifications de la structuration membranaire induites dans la signalisation des réponses de défense des plantes

Abstract : Spatial distribution of pasma membranes (PM) components is tightly regulated to provide the cell an optimal physiological state. The level of order degree is a suitable parameter to study PM organization, reflecting the intensity of interactions taking place between PM components and so the level of their packing. During our work, we used the environment sensitive probe di-4-ANEPPDHQ to assess the level of order degree of tobacco BY-2 cells PM in different situations: during the time-course of cell regeneration and in the particular case of an elicitation by cryptogein.We measured that the level of order degree of PM is modulated during the slow process of cell regeneration. This regulation isn’t related to the cell wall neo-synthesis neither the cell morphology, but is correlated to the differentiation state. The mapping of the level of order degree along the PM perimeter of protoplasts and suspension cells revealed a global common organization with a mosaic like distribution of domains (288X288 nm) exhibiting high diversity of level of order degree. The two models differed by the organization of this mosaic, the cell PM exhibiting enrichment in highest ordered domains in a specific area between two adjacent cells. Then, we discus about a possible involvement of membrane trafficking in the regulation of the level of order degree allowing specific targeting of lipids/proteins, and subsequent cellular identity acquisition.A pharmacological approach allowed the identification of the reactive oxygen species involved in the PM reorganization observed at the surface of tobacco BY-2 cells in response to cryptogein. We report that H2O2 has similar effects on the PM level of order degree compared to cryptogein’s one, both acting doses dependently. Furthermore, a partial inhibition of the H2O2 accumulation occurring in response to cryptogein is linked to a partial inhibition in the increase of the level of order degree usually induced by cryptogein. Those results suggest that H2O2 could finely regulates The PM level of order degree during the response of tobacco cells to cryptogein. The potential mechanisms involved has been studied. Two current hypotheses were studied in parallel, and both were rejected. The first one involves a modification of PM composition by an arrival of ordered domain to the PM. In the second one, a de novo formation of PM component structure. So, we discuss about a new role for H2O2, which would act directly on the PM level of order degree.
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Nelson Laurent. Caractérisation des mécanismes régulant les modifications de la structuration membranaire induites dans la signalisation des réponses de défense des plantes. Biodiversité et Ecologie. Université Bourgogne Franche-Comté, 2020. Français. ⟨NNT : 2020UBFCK026⟩. ⟨tel-02893238⟩

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