Comprehensive identification of terpene synthase genes from a traditional medicinal plant Angelica archangelica

Angelica archangelica L. is a traditional medicinal plant with a Nordic origin and produces an unusual number and types of terpenoids. The unique terpenoid composition in A. archangelica likely arises from involvement of terpene synthases (TPSs) with different specificities, none of which has been identified. As the first step to identify TPS isozymes responsible for the terpenoid chemodiversity in A. archangelica, we produced a transcriptome catalogue using RNAs extracted from leaf, tap roots, and dry seeds and identified 11 putative TPS genes (AaTPS1 through AaTPS11). Phylogenetic analysis predicted that AaTPS1 through AaTPS5 belong to monoterpene synthase cluster, AaTPS6 through AaTPS10 to sesquiterpene synthase cluster, and AaTPS11 to diterpene synthase cluster. We then carried out in vivo enzyme assays of AaTPS isozymes using recombinant Escherichia coli systems to examine their enzyme activities and specificities. Nine isozymes (AaTPS2 through AaTPS10) displayed TPS activities with specificities consistent with their phylogenetics, except that AaTPS5 displayed a strong sesquiterpene synthase activity along with a weak monoterpene synthase activity. We also analyzed terpenoid volatiles in the flower, immature seeds, mature seeds, leaf, and tap roots of A. archangelica by gas chromatography-mass spectrometry, and 15 monoterpenoids and 11 sesquiterpenoids were identified. The mature seeds accumulated monoterpenoids most abundantly, with a-phellandrene being the most prominent component.Alpha-pinene and beta-myrcene were abundant in every organ examined. The in vivo assay results of AaTPS isozymes suggested that the AaTPS isozymes identified in this study are at least partly involved in the establishment of chemodiversity of terpenoid volatiles in this plant.