A Plasma Membrane Nanodomain Ensures Signal Specificity during Osmotic Signaling in Plants

In the course of their growth and development, plants have to constantly perceive and react to their environment. This is achieved in cells by the coordination of complex combinatorial signaling networks. However, how signal integration and specificity are achieved in this context is unknown. With a focus on the hyperosmotic stimulus, we use live super-resolution light imaging methods to demonstrate that a Rho GTPase, Rho-of-Plant 6 (ROP6), forms stimuli-dependent nanodomains within the plasma membrane (PM). These nanodomains are necessary and sufficient to transduce production of reactive oxygen species (ROS) that act as secondary messengers and trigger several plant adaptive responses to osmotic constraints. Furthermore, osmotic signal triggers interaction between ROP6 and two NADPH oxidases that subsequently generate ROS. ROP6 nanoclustering is also needed for cell surface auxin signaling, but short-time auxin treatment does not induce ROS accumulation. We show that auxin-induced ROP6 nanodomains, unlike osmotically driven ROP6 clusters, do not recruit the NADPH oxidase, RBOHD. Together, our results suggest that Rho GTPase nano-partitioning at the PM ensures signal specificity downstream of independent stimuli. [Display omitted] •An isoform of ROP GTPase mediates ROS signaling and plant responses to osmotic signaling•Osmotic signaling induce nanodomains that contain activated ROP6•Interaction of ROP6 with RBOHs enriches nanodomains locally•Auxin induced nanodomains containing ROP6, but not RBOHs The mechanisms by which plants perceive and transduce osmotic signal remains incompletely understood. Here, Smokvarska et al. find that ROP6 forms nanodomain in response to osmotic signal. Then, ROP6 nanodomain recruits osmotic specific effectors that ensure downstream signal specificity.