Plant endogenous signalling peptides shape growth, development and adaptations to biotic and abiotic stress. We recently identified C-TERMINALLY ENCODED PEPTIDEs (CEPs) as novel immune-modulatory peptides (phytocytokines) in Arabidopsis thaliana. CEPs induce immune outputs and are required to mount resistance against the leaf-infecting bacterial pathogen Pseudomonas syringae pv. tomato. CEPs are categorized into different sequence divergent groups with distinct receptor requirements for signal induction. We showed that canonical group I CEPs are perceived by the tissue-specific CEP RECEPTOR 1 (CEPR1) and CEPR2, while the non-canonical CEP4 additionally binds to and signals through the phylogenetically related RECEPTOR-LIKE KINASE 7. Moreover, new data shows that group II CEPs are specifically recognized by CEPR2, revealing surprising receptor-ligand complexity among CEP modules. Canonical group I CEPs coordinate a previously unknown molecular crosstalk between the plant`s nitrogen (N) status and immunity, suggesting that CEPs can integrate diverse stress stimuli. I will present data on the complexity of CEP perception by sequence-divergent ligands and the role for plant immunity and beyond.
