Advances in the roles of SCOOP peptides and the receptor-like kinase MIK2 in plant stress responses

To cope with complex and dynamic environmental stresses, plants have evolved sophisticated cell-surface sensing systems. In recent years, the Brassicales-specific SERINE RICH ENDOGENOUS PEPTIDE (SCOOP) family and its receptor, MALE DISCOVERER 1-INTERACTING RECEPTOR-LIKE KINASE 2 (MIK2), have been established as a crucial module for the perception of extracellular danger signals in plants. The SCOOP peptides, the MIK2 receptor, and the signaling module they constitute not only play a central role in defending against biotic stresses such as pathogens and herbivores, as well as responding to abiotic stresses such as drought and salinity, but also coordinate the growth-defense trade-off in plants through complex signaling networks. This review systematically summarizes the biosynthesis mechanisms and stress responses of SCOOP peptides, explores the functional divergence of the MIK2 receptor under different stress conditions, and provides an in-depth analysis of the structural basis and downstream signal transduction mechanisms of the SCOOP-MIK2 module. Finally, we highlight the application potential of SCOOP, MIK2, and their signaling module in crop resistance improvement, aiming to provide a theoretical foundation for fundamental research on plant immune receptor networks, molecular breeding for stress tolerance, and the development of environment-friendly peptide preparations.