Cyclotides from Clitoria ternatea: Genomic Organization, Biosynthesis, and Roles in Plant Defense

Clitoria ternatea, commonly known as butterfly pea, is a perennial legume widely recognized for its ornamental and medicinal value. Beyond its characteristic anthocyanin-rich blue flowers, the plant produces cyclotides, a type of ultra-stable, cyclic cystine-knot peptide, with exceptional biological functions. Unlike other cyclotide-bearing families that carry independent cyclotide genes, C. ternatea integrates cyclotide domains into albumin-1 genes, replacing β-chain domains through divergent or convergent evolution. Genomic and transcriptomic studies reveal a large repertoire of albumin-1 loci and associated biosynthetic enzymes, including asparaginyl endopeptidases (butelase-1), protein disulphide isomerases, and peptidyl-prolyl isomerases, which orchestrate the cyclization, folding, and stabilization of cyclotides. Transcriptome analyses further demonstrate tissue-specific expression patterns, with distinct cyclotides such as cliotides T2 and T3 enriched in flowers and pods, and cliotides T8-T10 specialized in seeds, reflecting adaptive responses to localized biotic stress. Functionally, C. ternatea cyclotides exhibit broad-spectrum defense properties, including insecticidal, bactericidal, nematicidal, and antifungal activities, primarily through membrane permeabilization and disruption of lipid bilayers. Their preferential affinity for phosphatidylethanolamine-rich membranes highlights their selective toxicity toward insect and microbial targets. Recent advances in synthetic biology exploit cyclotides' structural stability as molecular scaffolds for therapeutic peptide design, with applications in immunomodulatory, antimicrobial, and anticancer drug development. This review consolidates genomic, transcriptomic, and functional insights into cyclotide biosynthesis and activity in C. ternatea, highlighting its evolutionary distinctiveness and biotechnological potential. Future research integrating multi-omics and spatial single-cell analyses can further unravel regulatory networks, defense dynamics, and translational applications of these unique plant peptides.