Maize immune signalling peptide ZIP1 evolved de novo from a retrotransposon

Abstract

Plants are subjected to different types of threats that require appropriate physiological responses to counteract them. Signalling peptides are produced under specific conditions and elicit physiological changes. PROZIP1 encodes such a signalling peptide, Zip1, that induces salicylic acid defence responses in maize (Zea mays) leading to a better protection against biotrophic pathogens. Despite salicylic acid pathway being conserved amongst plants, we observed that Zip1 only occurs in the Zea genus. PROZIP1s evolution is associated with transposons, as it resides in the terminal repeat of a retrotransposon from the Gyma family. We traced back the mutations that were encountered by this transposon and found that PROZIP1 emerged de novo in Zea. This emergence likely occurred less than 728,000 years ago. In conclusion, we describe the evolution of a recently emerged plant immune signalling peptide from a transposon sequence.