The prominent role of water in the plant life provides the motivation for a number of scientific groups to investigate the role of water channels, aquaporins (AQPs), in the plant water relations. AQPs are present in all the living organisms that have been researched to date. They transport water as well as small neutral solutes across the cell membranes.
The understanding of the AQP molecular functionality and structure progressed considerably during the last decade. In spite of that, the mechanism by which the AQP activity is being regulated at the plant cell level is still poorly understood. Our main objectives are to achieve a better understanding of the mechanism controlling the water permeability at the level of a single cell via the regulation of its plasma membrane AQPs, and to correlate this mechanism with the whole plant-water relationship.
Two major mechanisms are likely to be involved: gating (conformational changes of the AQPs) and trafficking (shuttling of small vesicles rich in AQPs). Specific AQ P gating models in plants are based mainly on data obtained after plant AQP expression in Xenopus oocytes (e.g. gating behaviour of AtPIP2;2. controlled by the cytosolic pH, of Soybean nodulin 26 controlled by phosphorylation). Trafficking models in plants are based on proteins other than AQPs (e.g. Auxin transporter PINI) or on mammalian AQP2 and AQP4 trafficking models. Identifying similar mechanisms directly involved in the regulation of plant cell water permeability should enable us to achieve these objectives.
To this end, we plan to investigate the plant AQP activity using specific chemicals known to affect the cellular concentrations of protons or Ca2+, second messenger ions involved in many regulations processes.
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