Abstract: Plant immune receptors such as the rice OsCERK1 protein is crucial for sensing immunogenic signal from pathogenic microbes and activate defenses. The immune activity of these immune receptors, however, must be tightly controlled to ensure normal growth when the pathogen is not present. How plants properly manage the speed of immune activation and stringent control is important for the survival of plants in a complex environment. A recent research discovered an E3 ligase, OsCIE1, that acts as a molecular brake controlling OsCERK1 activation in the absence of the immunogenic signal chitin. OsCIE1 inhibits the kinase activity of OsCERK1 by ubiquitination, thereby negatively regulating immunity. Upon perception of chitin, OsCERK1 phosphorylates OsCIE1 to inhibit the E3 ligase activity, thereby releasing the brake and allowing robust activation of defenses.

Key words: immune receptor, rice, disease resistance, post-translational modification, ubiquitin, phosphorylation