Molecular mechanisms of chitin recognition and immune signaling by LysM-receptors

• OsCEBiP is the major receptor for chitin elicitor binding in rice.
• The central LysM (LysM1) of OsCEBiP plays an important role for chitin binding.
• Ligand-induced, sandwich-type dimerization of OsCEBiP triggers defense signaling.
• OsCERK1 is a “bifunctional receptor” for defense and symbiosis signaling.

Plants have the ability to recognize microbe-associated molecular patterns (MAMPs) and initiate various defense responses. Chitin is a representative fungal MAMP that triggers defense signaling in a wide range of plant species. In rice, OsCEBiP and OsCERK1 form a receptor complex and play critical roles in chitin-triggered defense signaling. Recently, we found the formation of a unique sandwich-type dimer of OsCEBiP plays an important role for activation of chitin signaling. We now understand why N-acetyl groups and the longer chitin-oligosaccharides are required for receptor binding. We also found OsCERK1 is a bifunctional molecule acting in defense and also in AM symbiosis.