Implication des aquaporines dans le fonctionnement hydraulique foliaire in planta

Abstract : Climate changes models predict a global reduction of rainfalls hence limiting plants water availability and increase water stress occurrence. A moderate water stress can lead to stomata closure thereby decreasing the plants photosynthetic activity and in extreme cases, xylem embolism due to the water column breakage. In order to limit such detrimental effects, plants permanently adjust their hydraulic resistances. Leaves are considered as the main bottleneck in plants water fluxes, thus understanding leaf resistance to water flux regulation is fundamental. Within known factors that can potentially influence leaf hydraulic resistance, the aquaporins (AQPs) might have a central role. Plasma membrane Intrinsic Protein (PIP) family members are AQPs acting as pores that selectively allow water to flow through cell membranes. This work aimed at characterizing leaf hydraulic conductance (Kleaf the inverse of resistance) and investigate the potential contribution of PIPs in five temperate tree species and in tree model: Poplar. Pioneer species have high Kleaf values, but the Kleaf increase in response to light is much lower than for non-pioneer ones. In walnut (Juglans regia) blue light is responsible of most of the Kleaf increase and PIP transcript modulation. Under non-limiting light and water availability, poplar leaf hydraulic conductance increases diurnally with a maximum reached at midday. This increase of Kleaf occurs in parallel with PIP transcript and protein accumulation in response to high irradiance. PIP gene expression is also under endogenous circadian regulation to some extent. The involvement of AQPs is demonstrated by the reduction of Kleaf using HgCl2.
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David Lopez. Implication des aquaporines dans le fonctionnement hydraulique foliaire in planta. Biologie végétale. Université Blaise Pascal - Clermont-Ferrand II, 2012. Français. ⟨NNT : 2012CLF22323⟩. ⟨tel-01913507⟩

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