Defective cuticle‐derived signals enhance extracellular <scp>ATP</scp> response and plant immunity

Extracellular ATP (eATP) acts as a damage-associated molecular pattern in both animals and plants. In plants, eATP is recognized by the purinergic receptors P2K1 and P2K2, which mediate responses to various environmental stresses. From a p2k1 suppressor screen in Arabidopsis thaliana, we identified two allelic mutants of the cutin biosynthesis gene, BODYGUARD (BDG). The BDG mutations specifically suppress p2k1 and p2k1p2k2 mutant defects in response to eATP. The suppression of p2k1 by bdg modifies plant defense against the necrotrophic fungal pathogen, Botrytis cinerea. In addition, the results show that the defective cuticle in bdg mutants generates cutin breakdown products, such as cutin monomers, which serve as signaling molecules to activate eATP response and plant immunity through an alternative eATP signaling pathway. Our data provide new insights into the signaling role of cutin and reveal the first link between the cuticle and eATP signaling.