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Exploration fonctionnelle d'aquaporines par modélisation structurale. Impact sur les conductances hydriques foliaires chez le peuplier

Abstract : Aquaporins (AQPs) are transmembrane proteins involved in water and other small polar solutes transport. Because of their essential role in cells homeostasis, they are conserved in all branches of life and constitute a wide and ancient protein family. The diversity of these water channels is striking in plants where it is common to find dozens of AQPs homologues in there genome. Despite a good understanding of the molecular mechanisms underlying AQPs functions and regulations, the conservation and the expression of that many genes in some species still rise questions. This diversity is well illustrated in poplar, the woody “plant model” species studied in our team, experiencing drought. In the leaves of trees undergoing severe water deficiency, 10 AQP homologues, which according to our current knowledge are supposed to function in the same way, are differentially expressed at a given time point. Moreover, half of them are up-regulated while the other half are down-regulated. In order to link this genetic diversity to a functional diversity, we studied water transport across AQPs at the atomic resolution through molecular simulations, focusing on this particular biological context of poplar leaves undergoing water deficiency. Starting from the available crystallographic structures resolved from human, bacteria and plants, we managed to : (i) highlight a new functional diversity in strict AQPs, (ii) propose a correction constant for the osmotic permeability coefficient (pf), a commonly used AQPs permeability indicator, (iii) propose the underlying molecular mechanism, (iv) contextualize this mechanism with poplar genetic diversity during drought and (v) extend the concept to the whole AQP family. Conjointly, preliminary results obtained regarding a plant AQP gating mechanism previously described as well as the study of Trichoderma spp. AQPs allowed us to : (i) open new research opportunities and (ii) unify our team’s prior works to propose an AQP functional archetype.
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Submitted on : Thursday, April 1, 2021 - 11:25:44 AM
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Robin Mom. Exploration fonctionnelle d'aquaporines par modélisation structurale. Impact sur les conductances hydriques foliaires chez le peuplier. Biochimie, Biologie Moléculaire. Université Clermont Auvergne, 2020. Français. ⟨NNT : 2020CLFAC050⟩. ⟨tel-03172144v2⟩

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