Phosphatidylinositol Phosphates role in cell compartmentalization and development in Arabidopsis thaliana

Orateur : Mathilde SIMON (INRA, Lyon)

Phosphoinositides are minor lipids of the membrane bilayer that provide docking sites on membrane compartments and contribute to their identity. We recently mapped the localization of the different phosphoinositide species in Arabidopsis, and found that they do not accumulate to a specific compartment but rather that each phosphoinositide is distributed to several compartments, albeit at different concentration. These data suggest that the “phosphoinositide code” hypothesis is not sufficient to explain membrane selectivity of lipid binding proteins in plants. Phosphoinositides are anionic lipids and we hypothesized that this physical property might also contribute to membrane identity by regulating surface charges. To investigate membrane electrostatic properties, we designed a set of genetically encoded biosensors able to report membrane surface charges. We found that the plasma membrane (PM) has a specific electrostatic signature that is controlled by the phosphoinositide PI4P. We further show that this PI4P-dependent electrostatic field controls the PM localization and function of several proteins involved in receptor kinase and phytohormone signaling. Our findings uncover that phosphoinositides not only act as biochemical landmarks but that they also regulate organelle identity by establishing their electrostatic fields. Our work shows that this physical lipid property is crucial for membrane homeostasis but also for plant development.

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