Intercellular lipid flow coordinates tissue-scale lipid gradients in plants

The lipid composition of biological membranes dictates cellular states and functions, yet how cells coordinate their lipid profiles across tissues remains unclear. In plant roots, the lipid phosphatidylserine forms a tissue-scale localization gradient that regulates Rho GTPase signaling in response to auxin and osmotic stress1–6. How this gradient emerges is unknown. Here, we show that direct phospholipid exchange between cells coordinates these lipid patterns. Combining in vivo phospholipid phototracing and localized induction of phosphatidylserine synthesis, we found that lipids move between cells through the numerous plasmodesmata-membrane bridges connecting them. The phosphatidylserine gradient arises from local synthesis by PHOSPHATIDYLSERINE SYNTHASE1 within a restricted epidermal zone, combined with intercellular phosphatidylserine diffusion. Producing and receiving cells exhibit distinct subcellular phosphatidylserine localization patterns, together generating the tissue-scale lipid gradient. These results reveal that direct cell-cell membrane connections act as conduits for lipid flow, coordinating membrane composition and signaling capacity across tissues.