FERONIA cytoplasmic domain: node of varied signal outputs

The receptor-like kinase (RLK) FERONIA (FER), located on the plasma membrane, belongs to the Catharanthus roseus RLK1-like kinase family (CrRLK1L) and participates in widespread biological processes in plants in a context-dependent fashion. Genetic studies in Arabidopsis illustrated the versatile roles that FER plays in fertilization, vegetative growth, defense and stress responses, cell-wall homeostasis, as well as protein synthesis. These studies also helped to identify genes and signal pathways involved in FER signal transduction. Despite increasingly larger numbers of studies discussing how FER senses its ligand, Rapid alkalinization factor (RALF) peptides, and further regulates downstream factors, few have shown the mechanisms of how FER mediates the specific regulation of downstream signals in context of the phosphorylation of its cytoplasmic domain. As understanding this would help in better understanding the diversity and complexity of FER function, this paper aims to review the roles of FER in regulating different signal outputs from the view of the role of its cytoplasmic domain.