CBL1-CIPK26-Mediated Phosphorylation Enhances Activity of the NADPH Oxidase RBOHC, but Is Dispensable for Root Hair Growth

The study demonstrated that the CBL1-CIPK26 complex phosphorylated and activated the NADPH oxidase RBOHC, enhancing ROS production in a Ca2+-dependent manner, specifically at residues S318 and S322. However, this phosphorylation was not necessary for normal root hair growth in Arabidopsis, as plants expressing a modified RBOHC S318/322A enzyme still showed sufficient ROS production for RH differentiation. This indicated that while CBL1-CIPK26-mediated phosphorylation is critical for RBOHC activity, it is dispensable for RH growth, suggesting alternative regulatory mechanisms in plants.