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Structure et fonctions de la protéine kinase OST1 dans la cellule de garde d'Arabidopsis thaliana

Abstract : Drought is a major environmental constraint, and plants have developed several protective strategies to survive this stress. Most plants first respond to drought by closing their stomatal pores to prevent water loss via transpiration. The phytohormone abscisic acid (ABA) mediates reduction of stomatal conductance in response to drought through its action on guard cells. The protein kinase OST1 has been identified as a key early component of ABA signal transduction in Arabidopsis guard cells. In this thesis, we investigated the mechanisms of OST1 activation in response to ABA in guard cells. We show that the recombinant fusion protein 10xHis-OST1 produced in E.coli is active and autophosphorylates. This allowed the identification of phosphorylated residues representing putative targets of upstream kinases or phosphatases. The importance of these residues was first investigated in vitro by studying biochemical activity of recombinant point mutated versions of OST1. The impact of these mutations in plants was then analysed by OST1 knock-out mutant complementation and OST1 kinase activity measurements after immunoprecipitation. We also studied the C-terminal domain of OST1 applying the same strategy with several truncated versions of OST1 kinase. This work identifies several conserved residues and regulatory features critical for OST1 kinase activity and function in guard cells. Finally, the detailed analysis of several ost1 alleles leads us to propose a dual function for OST1 in guard cells and vascular tissues, controlling waterloss at both levels under drought conditions.
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Contributor : Christophe Belin Connect in order to contact the contributor
Submitted on : Tuesday, August 14, 2007 - 10:41:34 AM
Last modification on : Saturday, July 3, 2021 - 3:45:15 AM
Long-term archiving on: : Friday, November 25, 2016 - 5:55:34 PM

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  • HAL Id : tel-00167031, version 1
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Christophe Belin. Structure et fonctions de la protéine kinase OST1 dans la cellule de garde d'Arabidopsis thaliana. Biologie végétale. Université Paris Sud - Paris XI, 2006. Français. ⟨tel-00167031⟩

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