Phytocytokine signaling integrates cell surface immunity and nitrogen limitation

Plant endogenous signaling peptides shape growth, development and adaptations to biotic and abiotic stress. Here, we identified C-TERMINALLY ENCODED PEPTIDEs (CEPs) as novel immune-modulatory peptides (phytocytokines) in Arabidopsis thaliana. Our data reveals that CEPs induce immune outputs and are required to mount resistance against the leaf-infecting bacterial pathogen Pseudomonas syringae pv. tomato. We show that effective immunity requires CEP perception by tissue-specific CEP RECEPTOR 1 (CEPR1) and CEPR2. Moreover, we identified the related RECEPTOR-LIKE KINASE 7 (RLK7) as a novel CEP4-specific CEP receptor contributing to CEP-mediated immunity, suggesting a complex interplay of multiple CEP ligands and receptors in different tissues during biotic stress. CEPs have a known role in the regulation of root growth and systemic nitrogen (N)-demand signaling. We now provide evidence that CEPs and their receptors promote immunity in an N status-dependent manner, suggesting a previously unknown molecular crosstalk between plant nutrition and cell surface immunity. We propose that CEPs and their receptors are central regulators for the adaptation of biotic stress responses to plant-available resources.