Plant non-canonical peptides: From identification to mechanisms

Plant peptides have emerged as key regulators of plant growth, development, immunity, and environmental adaptation. Earlier studies in crops have demonstrated the potential application of certain peptides, such as systemin and Plant Elicitor Peptides (PEPs), to improve disease resistance. Based on the structure and function, these peptides are typically classified as canonical peptides (CPs), non-canonical peptides (NCPs), and non-ribosomal peptides (NRPs). Advances in peptidogenomics and mass spectrometry have enabled the genome-wide discovery of numerous endogenous peptides, including those translated from untranslated regions (UTRs) and non-coding RNAs, greatly expanding the plant peptidome. This review provides a comprehensive overview of the peptides, their classification, biosynthesis, and functional mechanisms in regulating various biological processes. Importantly, this review systematically summarizes the historical development and recent advances in strategies used to identify plant peptides. Despite substantial progress, peptide discovery and functional annotation remain challenging. Therefore, we finally propose that high-throughput technologies, functional genomics, and synthetic biology need to be integrated to reveal the potential of plant peptides in crop improvement and cross-disciplinary innovation.