The juxtamembrane domains of Arabidopsis CERK1, BAK1, and FLS2 play a conserved role in chitin-induced signaling.

Arabidopsis thaliana CERK1 is an essential receptor-like kinase in the chitin signal transduction pathway. The juxtamembrane (JM) domain of CERK1 regulates the kinase activity of this receptor. Here we demonstrate that the JM domains of LysM-RLKs, CERK1, and OsCERK1 play a functionally conserved role in the activation of chitin signaling in Arabidopsis. The C-termini of the JM domains of both CERK1 and OsCERK1 are indispensable for their function. Moreover, after replacing the JM domain of CERK1 with that of the nonhomologous RLK, BAK1 (CJBa) or FLS2 (CJFl), the chimeric CERK1 receptors maintained their ability to activate chitin signaling in Arabidopsis. Interestingly, the heterologous expression of CJBa and CJFl did not induce cell death in Nicotiana benthamiana leaves. These results suggest that the JM domains of CERK1, BAK1, and FLS2 play a conserved role in chitin signaling via a mechanism not related to sequence homology.