Diverse phytocytokines derived from conserved subtilase scaffolds co-evolved with clustered receptors to confer defence responses in legumes.

Plant peptide hormones orchestrate growth, development and immunity by engaging membrane-resident receptor kinases. GmSubPEP, a defence-eliciting peptide derived from a subtilase precursor, was initially isolated from soybean leaf extracts. Here we uncover an unexpected expansion of GmSubPEP variants with highly diverse sequences, yet each capable of triggering robust, tissue-specific pathogen resistance. Integrated transcriptomic and phosphoproteomic profiling shows that individual GmSubPEPs differentially activate overlapping and unique immune pathways, enabling fine-tuned defence modulation. Strikingly, genes generating these peptides and their receptors, termed GmSubPEP Receptors (GSPRs), are physically interspersed within a genomic cluster, and GSPRs exhibit differential binding affinities for their cognate peptide ligands. By unveiling how conserved subtilase precursor scaffolds diversify into specialized ligand-receptor pairs across legume lineages, our work reveals the role of SubPEP-GSPR modules in plant-microbe interactions and provides a framework for mining and engineering peptide-receptor modules to strengthen crop immunity.