A Dimerization-dependent Allosteric Activation for Receptor-like Kinase in Plants

ABSTRACT Receptor-like kinases (RLKs) are essential in plants and phosphorylation is a critical step for their function. Interestingly, RLKs have many non-catalytic kinases/ pseudokinases and the biochemical basis for these pseudokinases remains unclear. FERONIA (FER) is an RLK with kinase activity, but the necessity of its kinase activity for genetic functions has been debated. Here, we uncovered that the kinase-deficient variant FER K565R can activate kinase activity in FER and its homologous through homo/heterodimerization-dependent allosteric activation. We further showed that reactive oxygen species (ROS) significantly promote the dimerization of FER family members. Next, we revealed that mutating the FER P740 within the αG-αH loop reduces FER dimerization and disrupts its allosteric activation, thus attenuating FER’s transphosphorylation for its substrate. This disruption in allosteric activation abolishes the genetic function of FER K565R , impacting ROS production and ABA-mediated stomatal movements. Additionally, we found that MEDOS1 (MDS1), a member of the FER family, is incapable of catalyzing phosphotransfer, but can boost the kinase activity of FER and HERK1 through allosteric activation. These findings settle the debate on FER’s inactivated forms, and reveal a new mechanism for allosteric activation of RLKs via redox signaling, enhancing our understanding of pseudokinases in plants. One-sentence summary FER activates kinase activity of homologous family members through allosteric activation.