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Aquaporin gating in maize roots has large impacts on integrated physiological processes
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International audience. The adjustment of water transport is fundamental to plant adaptation to many challenging environmental conditions. The discovery of aquaporins as membrane channels facilitating water transfer and recent insights into their gating properties have opened new avenues for elucidating regulation mechanisms at a molecular level. But their significance for whole plant adaptation remains poorly documented. This work aims to integrate advances in molecular biology of aquaporin gating with whole plant hydraulics and hydraulically controlled processes. Particularly, the significance of aquaporin gating in roots for stomatal functioning and growth of leaves was investigated. We induced aquaporin gating in maize roots by acid load, H2O2 and anoxia. Under all these conditions, aquaporin gating decreased cell turgor in the leaf elongation zone and dramatically reduced leaf growth. However these effects could only be observed when the plant transpired substantially attributing a critical role for aquaporins under high evaporative demand. Negligible effects of aquaporin gating on transpiration were observed indicating that aquaporin gating did not induce stomatal closure. Overall, we show that aquaporin gating modifies the hydraulic architecture of the whole plant with consequences for plant growth but not for transpiration. Turgor measurements demonstrate that leaf growth responses to aquaporin gating in roots are hydraulically controlled. Remarkably, plant growth responses to anoxia are also mediated by changes in cell turgor suggesting a common hydraulic signalling mechanism. We demonstrate that conditions affecting aquaporin activity in plant roots are determinant for whole plant tolerance to environmental stresses.
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