Endogenous plant danger signaling peptides – an unwanted ingredient in a herbivore's diet?

Abstract: The family of Arabidopsis danger peptides (AtPeps) as well as their respective membrane receptors Pep-Receptor1 (PEPR1) and PEPR2 are induced upon wounding, biotic stress, and the application of Jasmonic Acid (JA). Upon receptor-ligand interaction, AtPeps induce a set of defence responses reminiscent of pattern-triggered immunity (PTI) and are therefore believed to act as so-called Danger-Associated Molecular Patterns (DAMPs). Since AtPeps lack a secretion signal, they are assumed to be only released from damaged cells and therefore are regarded as a monitoring system for cellular integrity. However, no clear role for AtPeps in the context of plant defence against biotic stress has been established yet. Here, we present a first line of evidence indicating an involvement of AtPep-signaling in herbivore defense. Using proPEPR::GUS reporter lines, we show that the AtPep-system is induced around the site of herbivore feeding. Moreover, this induction was independent of wounding but specific for the recognition of insect saliva (regurgitant). Potentially linking this involvement in insect feeding recognition to immune responses, we additionally show that besides standard PTI responses, the application of AtPeps induces the accumulation of JA, a master hormone in herbivore defense.