Abstract: The Arabidopsis AtPeps emerge as new paradigms for plant endogenous danger peptides. Upon detection by the two PRRs (pattern recognition receptors) PEPR1 and PEPR2 (Pep-receptor 1 and 2) they trigger a PTI (pattern-triggered immunity)-like response. AtPeps reside in the C-terminus of the small precursor proteins PROPEPs and are thought to be released under yet unknown circumstances. Recently, based on sequence and functional similarity, a PROPEP-like precursor protein as well as AtPep-like peptide have been identified in Zea mays plants, designated ZmPROPEP1 and ZmPep1, respectively. However, no data was presented on whether maize could detect AtPeps and vice versa. Our work shows that maize plants are insensitive to AtPeps and likewise, Arabidopsis plants do not recognize ZmPep1. Moreover, AtPep1 detection seems mainly limited to the family of Brassicaceae. Intriguingly, based on sequence analyses we identified AtPep-like peptides and corresponding PROPEP orthologs in most of the currently sequenced genomes of higher plants. Thus, we will now investigate, if these peptides are functional orthologs of AtPeps. Therewith we might show that the danger signaling system consisting of AtPep-like peptides, PROPEPs and PEPRs is widespread within the kingdom of higher plants, but that it diverged from a common ancestor towards an incompatibility between distantly related AtPep-like peptides.