In plants, the movement of water and small neutral solutes across the plasma membrane (PM) is dependent on the number and activity of water channels, named aquaporins (AQP). Little is known about mechanisms by which AQPs reach their final destination. Recent studies have shown that PIP (Plasma membrane Intrinsic Protein) aquaporins belonging to two subgroups, PIP1 and PIP2, physically interact to regulate their trafficking and the cell membrane water permeability. Therefore, this mechanism might play a pivotal role for the regulation of PIP functions. The main objective of the project is to generate detailed knowledge about the mechanisms regulating the intracellular trafficking of PIP1 and PIP2 aquaporins and the implication of their mutual interaction. To achieve this goal, 4 work packages have been defined. 1) We will characterise protein motifs responsible for ER retention of PIP1s and PM trafficking of PIP2s. 2) The amino acid residues responsible for the physical interaction between PIP1 and PIP2 isoforms will be determined. 3) We will investigate the transport capacity and selectivity of PIP hetero-oligomers. 4) Mechanisms governing subcellular PIP redistribution and dynamics upon specific stimuli will be characterised. The project represents a fundamental scientific approach providing valuable insights into hetero-oligomer formation, sorting and spatial redistribution of PIPs and will clearly advance the “state of the art” of the plant AQP research. It will generate a highly relevant basis for the uncovering of specific AQP functions in cells, tissues and thus in the metabolism of plants. Furthermore, these data will be crucial for the use of AQPs in biotechnological or plant breeding strategies aiming at a modulated water or solute transport leading to a higher drought resistance or an improved nutrient uptake or distribution in plants. Such traits demand a precise localisation of AQPs rather than a spatially uncontrolled modulation of AQP expression.
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