Defense Against Pathogens: Structural Insights into the Mechanism of Chitin Induced Activation of Innate Immunity

Pattern recognition receptors on the plant cell surface mediate the recognition of microbe-associated molecular patterns, in a process which activates downstream immune signaling. These receptors are plasma membrane-localized kinases which need to be autophos-phorylated to activate downstream responses. Perception of attacks from fungi occurs through recognition of chitin, a polymer of an N-acetylglucosamine which is a characteristic component of the cell walls of fungi. This process is regulated in Arabidopsis by chitin elicitor receptor kinase CERK1. A more complex process characterizes rice, in which regulation of chitin perception is operated by a complex composed of OsCERK1, a homolog of CERK1, and the chitin elicitor binding protein OsCEBiP. Recent literature has provided a mechanistic description of the complex regulation of activation of innate immunity in rice and an advance in the structural description of molecular players involved in this process. This review describes the current status of the understanding of molecular events involved in innate immunity activation in rice.