Identification Using Bioinformatics Tools of Cationic Amino Acid Transporter (CAT) Genes in Two Wild Ancestors of Sweetpotato

Sweetpotato [Ipomoea batatas (L.) Lam.] is one of the world’s most important food crops, and its wild relatives represent valuable genetic resources for improving stress tolerance and crop performance. Among amino acid transporters (AATs), cationic amino acid transporters (CATs) play fundamental roles in amino acid (aa) uptake, nitrogen (N) allocation, plant development, and responses to environmental stresses. However, the CAT gene family has not yet been systematically characterized in Ipomoea species. Here, we performed a comprehensive genome-wide identification and characterization of CAT genes in the diploid sweetpotato relatives I. trifida and I. triloba. A total of 21 CAT genes were identified, comprising 13 members in I. trifida and eight in the I. triloba genome. Comparative analyses revealed substantial variation in gene structure and protein physicochemical properties, whereas conserved motifs, phylogenetic relationships, and synteny supported a high degree of evolutionary conservation across species. Duplication analyses detected only segmental duplication pairs (three in I. trifida and two in I. triloba), all evolving under purifying selection. Transcriptome analyses further revealed pronounced tissue-specific expression patterns and differential transcriptional responses to drought, salt, cold, and heat stresses, suggesting functional diversification among CAT family members. Collectively, these findings provide the first comprehensive characterization of the CAT gene family in wild Ipomoea species, offer new insights into its evolutionary history, and identify candidate genes for future functional studies and sweetpotato breeding programs aimed at improving abiotic stress tolerance.