"In plants, receptor kinases form the largest family of plasma membrane (PM) receptors and they are involved in virtually all aspects of the plant life, including development, immunity and reproduction. In animals, key molecules that orchestrate the recruitment of signaling proteins to membranes are anionic phospholipids (e.g. phosphatidylinositol phosphate or PIPs). Besides, recent reports in animal and yeast cells suggest the existence of PM nanodomains that are independent of cholesterol and lipid phase and rely on anionic phospholipids as well as electrostatic protein/lipid interactions. Strikingly, we know very little on the role of anionic phospholipids in plant signaling. However, our preliminary data suggest that BKI1, an inhibitory protein of the steroid receptor kinase BRI1, interacts with various PIPs in vitro and is likely targeted to the PM by electrostatic interactions with these anionic lipids. These results open the possibility that BRI1, but also other receptor kinases, might be regulated by anionic phospholipids in plants. Here, we propose to analyze the function of anionic phospholipids in BRI1 signaling, using the root epidermis as a model system. First, we will ask what are the lipids that control membrane surface charge in this tissue and recruit BR-signaling component to the PM. Second, we will probe the presence of PIP-enriched nanodomains at the plant PM using super-resolution microscopy techniques and investigate the roles of these domains in BRI1 signaling. Finally, we will analyze the function of the BKI1-related plant-specific family of anionic phospholipid effectors in plant development. In summary, using a transversal approach ranging from in vitro studies to in vivo validation and whole organism physiology, this work will unravel the interplay between anionic phospholipids and receptor signaling in plants."