PEP7 is the endogenous ligand for the receptor kinase plasma membrane-intrinsic sucrose-induced receptor kinase 1 (SIRK1). Plant peptide hormones are usually perceived by membrane-localized receptors, followed by induction of signaling pathways to mediate diverse functions, and many of these receptors have been identified as receptor kinases, the largest family of receptor proteins in plants. SIRK1 and Qian Shou kinase 1 (QSK1) are the receptor/co-receptor pair involved in the regulation of aquaporins in response to osmotic conditions induced by sucrose and the PEP7/SIRK1/ QSK1 complex represents a crucial perception and response module that mediates sucrose-controlled water flux in plants and lateral root development.
