Spatial organization of ROS signaling at the plasma membrane

Genetic studies in Arabidopsis have identified a lot of the participants in signal transduction pathways, but often its less clear precisely where they function. As an example, although it is well known that H₂O₂ (hydrogen peroxide) production by RBOHs in the apoplast triggers many downstream cellular events, exactly where the signal is effective and how it reaches the cytosol is unknown. In a new study, Poitout et al. used a sensitive H₂O₂ reporter, HyPer7, to investigate H₂O₂ location in plant cells. They fused it to ROP6, a small GTPase which had previously been associated with RBOHs, and found that, upon osmotic stress, an H₂O₂ burst localizes with ROP6 nanodomains on the cytosolic side of the plasma membrane, demonstrating that these nanodomains can generate gradients of small diffusible molecules. Interestingly, the authors found that PIP2;7 channels (a specific class of aquaporin water channels that also transport H₂O₂), both co-localize with the ROP6 nanodomains and  are necessary for H₂O₂ to effectively diffuse across the plasma membrane. It will be interesting to explore further the roles of these ROS signaling nanodomains. (Summary by Mary Williams @PlantTeaching.bsky.social) bioRxiv https://doi.org/10.64898/2026.01.19.698185