Plant Peptides on the Rise: From Historical Insight to Future Applications.

Plant peptides constitute a rapidly expanding class of signalling molecules essential to plant physiology, mediating key processes such as development, stress adaptation, and immune responses. This review traces the history of plant peptide research, from the seminal discovery of systemin to the recent identification of non-canonical peptides (NCPs) translated from small open reading frames (sORFs) in non-coding RNAs. We delineate the distinct biosynthetic pathways of canonical peptides (CPs), which undergo proteolytic processing and post-translational modifications, and NCPs, which are directly translated, often without further processing. The diverse biological functions of these peptides span development, reproduction, abiotic stress tolerance, biotic defence, and antimicrobial activity. Furthermore, we discuss emerging agricultural applications, including genetic engineering of peptides, exogenous peptide application, and trait optimization informed by natural peptide variation. Beyond agriculture, many plant peptides exhibit therapeutic potential due to their antimicrobial and anticancer properties. Despite significant advances, challenges remain in functional validation, field application, and scalable production. Future progress will depend on the integration of multi-omics approaches, artificial intelligence (AI)-driven prediction, and precision genome editing to fully harness the transformative potential of plant peptides for crop improvement and novel biopharmaceuticals.