GOLVEN secretory peptides regulate auxin carrier turnover during plant gravitropic responses

Growth and development are coordinated by an array of intercellular communications. Known plant signaling molecules include phytohormones and hormone peptides. Although both classes can be implicated in the same developmental processes, little is known about the interplay between phytohormone action and peptide signaling within the cellular microenvironment. We show that genes coding for small secretory peptides, designated GOLVEN (GLV), modulate the distribution of the phytohormone auxin. The deregulation of the GLV function impairs the formation of auxin gradients and alters the reorientation of shoots and roots after a gravity stimulus. Specifically, the GLV signal modulates the trafficking dynamics of the auxin efflux carrier PIN-FORMED2 involved in root tropic responses and meristem organization. Our work links the local action of secretory peptides with phytohormone transport. Root growth factor (RGF) or GOLVEN (GLV) secreted peptides have previously been implicated in meristem regulation. Whitford et al. now show that RGF/GLV peptides induce rapid relocalization of the auxin efflux regulator PIN2, regulate auxin gradients, and modulate auxin-dependent root responses to specific stimuli.