Identification of novel peptide family that regulates defense response and root development in Arabidopsis thaliana

Small secreted peptides are important in plant development and stress response. Even though numerous genes have the potential to produce such peptides, the vast majority of them have not yet been characterized for their biological functions. In this study, using a targeted in silico approach, we identified a family of 14 Arabidopsis genes encoding precursors of serine-rich endogenous peptides (PROSCOOP). Transcriptomic analyses revealed that one member of this gene family is involved in processes linked to biotic and oxidative stress as well as root growth. Plants defective in this gene were less susceptible to Erwinia amylovora infections and showed an enhanced root growth phenotype. We identified a conserved motif present in Brassicaceae homologs indicating that the protein could be the precursor of a small secreted peptide. Exogenous application of this synthetic peptide induced various defense responses in Arabidopsis. Our findings show that it has numerous properties of damage/danger-associated molecular pattern (DAMP). In conclusion, we uncover a gene family with all structural features of post-translationally-modified peptides that modulate defense responses and root development. That could provide new targets for breeding strategies for crops to adapt to challenging environments.