Functional characterization of triterpene synthases in .

(Linn.) J. Sm., a tree fern in the Dicksoniaceae family, is an economically important industrial exported plant in China and widely used in Traditional Chinese Medicine. produces a range of bioactive triterpenes and their metabolites. However, the biosynthetic pathway of triterpenes in remains unknown. To clarify the origin of diverse triterpenes in , we conducted transcriptome sequencing and analysis of rhizomes and leaves to identify the candidate genes involved in triterpene biosynthesis. Three triterpene synthases (CbTSs) candidate genes were obtained. All of them were highly expressed in rhizomes, consisting of the accumulation pattern of triterpenes in . To characterize the function of these CbTSs, we constructed a squalene- and oxidosqualene-overproducing yeast chassis by overexpressing all the enzymes in the MVA pathway under the control of GAL-regulated promoter and disrupted the GAL80 gene in simultaneously. Heterologous expressing CbTS1, CbTS2, and CbTS3 in engineering yeast strain produced cycloartenol, dammaradiene, and diploptene, respectively. Phylogenetic analysis revealed that CbTS1 belongs to oxidosqualene cyclase, while CbTS2 and CbTS3 belong to squalene cyclase. These results decipher enzymatic mechanisms underlying the origin of diverse triterpene in .