More than an on-and-off switch: Post-translational modifications of plant pattern recognition receptor complexes.

Sensing microbe-associated molecular patterns (MAMPs) by cell surface-resident pattern recognition receptors (PRRs) constitutes a core process in launching a successful immune response. Over the last decade, remarkable progress has been made in delineating the mechanisms of PRR-mediated plant immunity. As the frontline of defense, the homeostasis, activities, and subcellular dynamics of PRR and associated regulators are subjected to tight regulations. The layered protein post-translational modifications, particularly the intertwined phosphorylation and ubiquitylation of PRR complexes, play a central role in regulating PRR signaling outputs and plant immune responses. This review provides an update about the PRR complex regulation by various post-translational modifications and discusses how protein phosphorylation and ubiquitylation act in concert to ensure a rapid, proper, and robust immune response.