Processing of plant peptide signals: critical steps mediated by subtilisins

Secreted peptides are pivotal mediators of intercellular signaling in plants, playing crucial roles in plant growth, development, and stress responses. While substantial progress has been made in understanding peptide perception and signal transduction mechanisms, the mechanisms underlying their biogenesis remain poorly understood. All secreted peptides require proteolytic processing to release their mature forms, and this processing is primarily carried out by subtilisin-like serine proteases (SBTs). SBTs are essential enzymes in plants, being involved in various developmental processes such as embryo development, seed formation, root growth, and organ abscission. This review elucidates the role of SBTs in the processing of secreted peptide precursors, highlighting their involvement in plant signaling during different developmental processes and stress responses. We also summarize recent advancements in understanding the mechanisms of SBT-mediated peptide processing. Key challenges, such as the not-well-conserved nature of SBT recognition sites and the low abundance of peptide signals, are explored alongside promising methodological approaches. Addressing these gaps is critical for advancing our understanding of plant peptide biogenesis and its implications for developmental biology and stress adaptation.