Chitin receptor-mediated activation of MAP kinases and ROS production in rice and Arabidopsis

Rapid induction of plant immune responses is essential to inhibit colonization and invasion by pathogens. Plants can recognize pathogen-associated molecular patterns (PAMPs) including fungal chitin and bacterial flagellin using pattern-recognition receptors (PRRs), which trigger the intracellular activation of mitogen-activated protein kinase (MAPK) cascades and the production of reactive oxygen species (ROS). MAPK activation and ROS production play pivotal roles in the induction of robust immune responses. Recent investigation of chitin- and flagellin-induced immune signaling revealed that receptor-like cytoplasmic kinases (RLCKs) connect PRR-mediated pathogen recognition to MAPK activation and ROS production. In addition, although the MAPK cascade is mediated by 3 sequentially activated protein kinases, MAPK kinase kinase (MAPKKK), MAPK kinase (MAPKK), and MAPK, how MAPKKKs are activated downstream of PRRs in plants has not been identified until recently. In this review, we summarize recent findings of RLCK-mediated MAPK activation and ROS production in rice and Arabidopsis.