Novel Aquaporin Regulatory Mechanisms Revealed by Interactomics.

PIP1;2 and PIP2;1 are aquaporins that are highly expressed in roots and bring a major contribution to root water transport and its regulation by hormonal and abiotic factors. Interactions between cellular proteins or with other macromolecules contribute to forming molecular machines. Proteins that molecularly interact with PIP1;2 and PIP2;1 were searched to get new insights into regulatory mechanisms of root water transport. For that, a immuno-purification strategy coupled to protein identification and quantification by mass spectrometry (IP-MS) of PIPs was combined with data from the literature, to build thorough PIP1;2 and PIP2;1 interactomes, sharing about 400 interacting proteins. Such interactome revealed PIPs to behave as a platform for recruitment of a wide range of transport activities and provided novel insights into regulation of PIP cellular trafficking by osmotic and oxidative treatments. This work also pointed a role of lipid signaling in PIP function and enhanced our knowledge of protein kinases involved in PIP regulation. In particular we show that 2 members of the receptor-like kinase (RLK) family (RKL1 (At1g48480) and Feronia (At3g51550)) differentially modulate PIP activity through distinct molecular mechanisms. The overall work opens novel perspectives in understanding PIP regulatory mechanisms and their role in adjustment of plant water status.