A peptide-receptor module links cell wall integrity sensing to pattern-triggered immunity.

Plants employ cell-surface receptors to perceive non- or altered-self, including the integrity of their cell wall. Here we identify a specific ligand-receptor module responsive to cell wall damage that potentiates immunity in Arabidopsis. Disruption of cell wall integrity by inhibition of cellulose biosynthesis promotes pattern-triggered immunity transcriptionally in a manner dependent on the receptor kinase MALE DISCOVERER 1-INTERACTING RECEPTOR-LIKE KINASE 2 (MIK2). Notably, while MIK2 can perceive peptides of the large SERINE RICH ENDOGENOUS PEPTIDE family, a single member of this family, SCOOP18, is transcriptionally induced upon cell wall damage and is required for subsequent responses such as lignification and immunity potentiation. Collectively, our results identify the SCOOP18-MIK2 ligand-receptor module as an important central hub, connecting plant cell wall integrity sensing with immunity.