Le couplage nitrate/proton au sein de l’échangeur AtClCa est essentiel à la physiologie de la plante en réponse aux fluctuations environnementales

Abstract : Nitrate is a major element for plant but its availability is very fluctuant in soils. Then, it is stored in vacuoles thanks to a nitrate/proton exchanger named AtClCa. In ClCs, exchangers but also channels were identified, the latest were suggested to be evolved from exchanger in which a mechanistic switch happened. In Arabidopsis thaliana, only exchangers are involved in nitrate management. Two conserved glutamate, E203 and E270 in AtClCa, are essential for protons transport in ClCs exchangers. The mutation of E203 into an alanine, a non-protonable amino acid (E203A) artificially produces such a mechanistic switch. To better understand the physiological importance of this exchange mechanism, a study was conducted in plants expressing the mutated form of AtClCa for this glutamate. In those plants, the vacuolar storage is highly restricted whereas the assimilation is favoured and the protein content increased. Despite that, the biomass production is decreased mostly because of a hydric homeostasis disruption. Those plants are also more sensitive to hydric and probably nitrogenous stress. The exchanger conservation is then required for plant growth whatever the environmental fluctuations. In parallel, the mutation E270A was introduced in planta to study its physiological importance. A preliminary analysis of plant biomass and nitrate and water contents was then performed in plants expressing the E270A mutated form of AtClCa and the results are presented in the second part of the manuscript.
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Julie Hodin. Le couplage nitrate/proton au sein de l’échangeur AtClCa est essentiel à la physiologie de la plante en réponse aux fluctuations environnementales. Biologie végétale. Université Paris-Saclay, 2018. Français. ⟨NNT : 2018SACLS181⟩. ⟨tel-02174202⟩

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