The rice LysM receptor‐like kinase OsCERK1 is required for the perception of short‐chain chitin oligomers in arbuscular mycorrhizal signaling

Summary The rice lysin‐motif (LysM) receptor‐like kinase Os CERK 1 is now known to have a dual role in both pathogenic and symbiotic interactions. Following the recent discovery that the Oscerk1 mutant is unable to host arbuscular mycorrhizal ( AM ) fungi, we have examined whether Os CERK 1 is directly involved in the perception of the short‐chain chitin oligomers (Myc‐ CO s) identified in AM fungal exudates and shown to activate nuclear calcium (Ca 2+ ) spiking in the rice root epidermis. An Oscerk1 knockout mutant expressing the cameleon NLS ‐ YC 2.60 was used to monitor nuclear Ca 2+ signaling following root treatment with either crude fungal exudates or purified Myc‐ CO s. Compared with wild‐type rice, Ca 2+ spiking responses to AM fungal elicitation were absent in root atrichoblasts of the Oscerk1 mutant. By contrast, rice lines mutated in Os CEB iP , encoding the LysM receptor‐like protein which associates with Os CERK 1 to perceive chitin elicitors of the host immune defense pathway, responded positively to Myc‐ CO s. These findings provide direct evidence that the bi‐functional Os CERK 1 plays a central role in perceiving short‐chain Myc‐ CO signals and activating the downstream conserved symbiotic signal transduction pathway.