Full-Length Transcriptome Analysis of Different Origins and Functional Characterization of Terpene Synthase in Atractylodes macrocephala Koidz.

Atractylodes macrocephala Koidz., a perennial medicinal herb of the Asteraceae family, holds significant therapeutic value in traditional medicine. It is primarily recognized for its ability to strengthen spleen and stomach functions and modulate gastrointestinal activity. In this study, the molecular mechanisms governing sesquiterpenoid biosynthesis in A. macrocephala were investigated through an integrated sequencing strategy combining next-generation sequencing (NGS) and single-molecule real-time (SMRT) sequencing. Transcriptomic analysis identified 17,846 differentially expressed genes (DEGs) in rhizomes from three geographical origins, including 5196 upregulated and 12,650 downregulated genes. Nine full-length terpene synthase (TPS) genes were successfully retrieved. Comprehensive functional characterization of these AmTPS genes was performed using amino acid sequence analysis, multiple sequence alignment, phylogenetic reconstruction, quantitative real-time PCR (qRT-PCR), and heterologous expression assays. AmTPS8 and AmTPS9 were assigned to the TPS-a subfamily. Notably, AmTPS8 displayed the highest transcript abundance in samples from the Yuexi region, whereas AmTPS9 was most highly expressed in rhizomes from the Bozhou region. Enzymatic assays demonstrated that AmTPS8 catalyzes the formation of bulnesol, while AmTPS9 exhibits juniper camphor synthase activity. Overall, this study provides important insights into terpenoid biosynthesis in A. macrocephala and establishes a molecular basis for future research aimed at enhancing sesquiterpenoid production and elucidating regulatory mechanisms within this medicinally important species.