Evolutionary and molecular insights into the terpene synthase gene (TPS) family in the medicinal plant Bidens alba

Terpenoids are important secondary metabolites in plants, valued for their pharmacological activities and economic significance. Terpene synthases (TPS) serve as the key enzymes in terpenoid biosynthesis. To explore the TPS gene family and their potential functions in Bidens alba, this study conducted a comprehensive analysis of TPS genes based on whole-genome data using bioinformatics approaches. A total of 84 BaTPS genes were identified and unevenly distributed across 37 chromosome-scale scaffolds. Phylogenetic analysis classified these genes into five subfamilies: TPS-a, TPS-b, TPS-c, TPS-e/f, and TPS-g. Among them, the TPS-a and TPS-b subfamilies contained the largest number of members, while the TPS-g showed significant expansion. Further investigation revealed that whole-genome duplication and segmental duplication were the main drivers of BaTPS gene family expansion, with purifying selection playing a predominant role in their evolution. Gene structure analysis showed that BaTPS genes exhibit highly conserved intron-exon organization. Motif analysis identified several conserved domains, including the characteristic "DDxxD" motif, along with the "RDR," "RRX(8)W," and "NSE/DTE" motifs. Promoter region analysis uncovered numerous cis-acting elements, particularly those responsive to light, methyl jasmonate (MeJA), and abscisic acid (ABA). Expression profiling using RNA-seq and RT-qPCR demonstrated tissue-specific expression patterns of BaTPS genes, with BaTPS02, BaTPS16, BaTPS41, BaTPS47, BaTPS53 and BaTPS60 highly expressed in floral organs. Subcellular localization showed that BaTPS16 and BaTPS41 are localized in cytoplasm. Collectively, these findings suggest that B. alba floral organs may be rich in diverse terpenoids. This study lays theoretical foundation for future functional analyses of the TPS gene family in B. alba and supports the development of its medicinally active compounds.