A tale of two systems: peptide ligand-receptor pairs in plant development.

Plants have developed intercellular signaling systems that use secreted peptides and plasma membrane-localized receptor-like kinases (RLKs). Although there has been little experimental evidence linking specific peptide ligands to receptors, recent studies of several ligand-receptor pairs have revealed their increasingly important roles in cell-cell communications during plant development. In this review, we focus on two specific families of plant peptides: the CLAVATA3/ENDOSPERM SURROUNDING REGION (CLE) peptide family and the EPIDERMAL PATTERING FACTOR (EPF) family, along with their corresponding RLKs. We discuss how these two unrelated peptide-mediated signaling systems control plant cell fate and development using similar receptor kinases as well as the mechanisms for how these peptide ligand-receptor pairs precisely regulate various distinct aspects of plant development at the level of ligand-receptor recognition and signal transduction.