Turgor reduction triggers FERONIA nanodomain assembly for osmosensing in plants

Osmotic stress reduces turgor pressure, relaxes the extracellular matrix, and may generate tensile forces at the cell wall-plasma membrane interface. While animal and yeast cells employ force sensor clusters for mechanosensing, turgor-sensing mechanisms in plants remain unclear. Here, we identify FERONIA (FER) as a cell wall-anchored turgor sensor in land plants. Turgor reduction triggers the assembly of FER into largely immobile nanodomains and activates its kinase activity, processes that depend on cell wall anchoring mediated by its malectin A domain. The extracellular domain is essential and sufficient for FER nanodomain formation, thereby initiating outside-in signaling. Together, our findings suggest that FER senses mechanical perturbations at the cell wall-plasma membrane interface during turgor reduction and provide mechanistic insight into osmosensing in walled organisms.