How a single receptor‑like kinase exerts diverse roles:lessons from FERONIA

FERONIA(FER)is a member of the Catharanthus roseus receptor-like kinase 1-like(CrRLK1L)protein subfamily,which participates in reproduction,abiotic stress,biotic stress,cell growth,hormone response,and other molecular mecha-nisms of plants.However,the mechanism by which a single RLK is capable of mediating multiple signals and activat-ing multiple cellular responses remains unclear.Here,we summarize research progress revealing the spatial–temporal expression of FER,along with its co-receptors and ligands determined the function of FER signaling pathway in multiple organs.The specificity of the FER signaling pathway is proposed to operate under a four-layered mechanism:(1)Spatial–temporal expression of FER,co-receptors,and ligands specify diverse functions,(2)Specific ligands or ligand combinations trigger variable FER signaling pathways,(3)Diverse co-receptors confer diverse FER perception and response modes,and(4)Unique downstream components that modify FER signaling and responses.Moreover,the regulation mechanism of the signaling pathway-appears to depend on the interaction among the ligands,RLK receptors,co-receptors,and downstream components,which may be a general mechanism of RLKs to maintain signal specificity.This review will provide a insight into understanding the specificity determination of RLKs signaling in both model and horticultural crops.