EWR1 as a SCOOP peptide activates MIK2-dependent immunity inArabidopsis

Phytocytokines are plant peptide signals perceived by plasma membrane-localized receptors in regulating plant immunity. It was recently reported that the phytocytokine SERINE-RICH ENDOGENOUS PEPTIDE12 (SCOOP12) is recognized by the receptor kinase MALE DISCOVERER 1-INTERACTING RECEPTOR-LIKE KINASE 2 (MIK2) and activates plant immune responses and resistance to pathogens in Arabidopsis. Here, we show that Arabidopsis ENHANCER OF VASCULAR WILT RESISTANCE 1 (EWR1) and four EWR1 close propeptide homologs encode functional SCOOP peptides, which are able to activate immune responses via MIK2 and BRASSINOSTEROID INSENSITVE 1 (BRI1)-ASSOCIATED RECEPTOR KINASE 1 (BAK1) and SOMATIC EMBRYOGENESIS RECEPTOR KINASE 4 (SERK4).