Phytocytokine signaling integrates cell surface immunity and nitrogen limitation

Little is known about plant genetic and biochemical components that coordinate immune responses with growth and environmental cues. C-TERMINALLY ENCODED PEPTIDEs (CEPs) control plant development and nitrogen demand signaling. Here, we identified CEP4 as an immune-modulatory peptide (phytocytokine) in Arabidopsis thaliana. CEP4 and related CEPs are important regulators of resistance to plant pathogenic bacteria and are perceived by the tissue-specific receptor kinases CEP RECEPTOR 1 (CEPR1), CEPR2 and the phylogenetically related RECEPTOR-LIKE KINASE 7 (RLK7). CEP4 promotes flagellin-triggered responses and we provide evidence that CEPs modulate cell surface immunity upon N limitation. We propose that CEPs integrate biotic and abiotic stress-associated signals to safeguard plant health.