Chromosome-scale genome assembly of Atractylodes lancea reveals AlTPS37, a sesquiterpene synthase associated with chemotype-specific eudesmol biosynthesis

Atractylodes lancea (Asteraceae) is an important medicinal plant widely used in traditional Chinese medicine, with sesquiterpenoids as its major bioactive components. However, the molecular basis of chemotype-specific sesquiterpenoid divergence in A. lancea remains unclear. To address this question, HS-GC/MS and GC-MS quantification revealed that the Hinesol chemotype (HO-type) exhibits significantly higher concentrations of hinesol, guaiol, and three eudesmol isomers (α-, γ-, β-eudesmol), while the Atractylon chemotype (AT-type) exhibits elevated atractylon, β-elemene, and β-caryophyllene concentrations. Using a chromosome-scale genome assembly of HO-type A. lancea (4.43 Gb, contig N50=101.66 Mb), we identified 74 terpene synthase (TPS) genes, among which nine were selected for functional characterization. Enzymatic assays showed that AlTPS37 , AlTPS70 , and AlTPS71 are involved in the biosynthesis of sesquiterpenoids enriched in the HO-type. AlTPS37 predominantly catalyzed the formation of γ-,α-, and β-eudesmol, whereas AlTPS70 and AlTPS71 contributed to the production of guaiol- and bulnesol-related sesquiterpenoids. Comparative analysis of two AlTPS37 haplotypes from HO- and AT-type plants, combined with site-directed mutagenesis, revealed that allelic functional divergence, together with higher AlTPS37 expression in the HO-type, contributed to distinct eudesmol accumulation patterns between the two chemotypes. Together, these findings identify AlTPS37 as an important TPS gene associated with chemotype-specific eudesmol accumulation and provide new insights into chemotype-associated sesquiterpenoid divergence in A. lancea .