RALF-like peptide improves the colonization of endophytic Colletotrichum tofieldiae through interacting with plant receptor-like kinase

Endophytes can colonize a host plant without inducing obvious disease symptoms. Elicitors from endophytes may play important roles in balancing endophyte colonization. We identified a novel endophytic elicitor from Colletotrichum tofieldiae, CtRALF, that has structural and functional characteristics similar to those of rapid alkalinization factor (RALF) peptides in Arabidopsis thaliana. We found that CtRALF can directly interact with the host plant receptor-like kinase FERONIA (FER). The colonization of FER mutant plants by hyphae of C. tofieldiae was obviously reduced compared with that on wild-type plants. Furthermore, the interaction of CtRALF with FER regulated symbiotic signals by triggering calcium waves, inhibiting reactive oxygen species bursts, increasing mitogen-activated protein kinase phosphorylation and reducing the stabilization of MYC2. Collectively, these results suggested that the RALF homologue of endophytes may improve their symbiosis by interacting with host plant-encoded FER.