RGI-GOLVEN signalling promotes FLS2 abundance to regulate plant immunity

Abstract Endogenous plant signalling peptides regulate developmental and growth-related processes. Recent research indicates that some of these peptides are classified as phytocytokines as they have regulatory functions during plant immune responses. However, the mechanistic basis for phytocytokine-mediated immune modulation remains largely elusive. Here, we identify GOLVEN2 (GLV2) peptides as novel phytocytokines in Arabidopsis thaliana . By peptide application, precursor overexpression and loss-of-function studies we show that GLV2 enhances sensitivity of plants to elicitation with the bacterial flagellin epitope flg22. GLV2 is perceived by ROOT MERISTEM GROWTH FACTOR 1 INSENSITIVE (RGI) receptors and RGI3 forms an flg22-induced complex with the flg22-receptor FLAGELLIN SENSITIVE 2, suggesting that RGIs are part of activated pattern recognition receptor signalling platforms. GLV2 perception increases posttranscriptional FLS2 abundance and RGIs promote FLS2 protein accumulation. Thus, GLV-RGI signalling controls above ground plant immunity via a novel mechanism of phytocytokine activity.