Along with the species evolution, plants have evolved ways to produce a different collection of terpenoids to accommodate its biotic and abiotic environment, and terpene synthase (TPS) is one of the major contributors to various terpene compounds. The timber of a monotypic and relictual conifer species of Cupressace, Taiwania cryptomerioides, has excellent durability, and one of the essential factors for Taiwania to resist decay and insect pests is sesquiterpene. Compared to other conifers, Taiwania has much higher abundance of cadinene-type sesquiterpenes, and the presence of cedrene-type sesquiterpenes. To understand sesquiterpene biosynthesis in Taiwania, we functionally characterized 10 T. cryptomerioides TPSs (TcTPSs) in vivo or in planta, which could catalyze sesquiterpene formation and potentially are involved in biosynthesis of diverse sesquiterpenoids in Taiwania. The distant phylogenetic relationship and the intron loss event of TcTPSs correlate to the differentiation of chemical profile Taiwania compared to other conifers. Furthermore, we identified TcTPS3 and TcTPS12 as δ-cadinene synthase, and TcTPS6 as cedrol synthase, which demonstrates the important contributions of dynamic evolution in TPSs to the chemical diversity in plants. Combining with functional characterization and comparison of catalytic residues, we conclude at least three catalytic routes for sesquiterpene biosynthesis in this species, and the skeleton diversity has been expended in T. cryptomeriodes.
Keywords: Biochemical enzyme characterization; Gymnosperms; Plant specialized metabolism; Sesquiterpene metabolism; Taiwania cryptomerioides; Terpene synthase.
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