RGI-GOLVEN signalling promotes FLS2 abundance to regulate plant immunity

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 INSENSITIVE (RGI) receptors and RGI3 forms an flg22-induced complex with the flg22-receptor FLAGELLIN SENSING 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.