부산대학교 도서관

Pentacyclic triterpenes are isoprene-derived secondary metabolites that are synthesized by the cyclization of 2,3-oxidos- qualene. Two pentacyclic triterpenoids, taraxasterol and ψ-taraxasterol, are particularly rich in dandelion and are useful candidates for pharmacologically active triterpenes. A multifunctional oxidosqualene cyclase (TcOSC1) of Taraxacum core- anum catalyzes the cyclization of 2,3-oxidosqualene into various triterpenes (taraxasterol, ψ-taraxasterol, δ-amyrin, β-amyrin, α-amyrin, and dammarenediol-II) which were demonstrated by heterologous expression in the yeast. Here, we evaluated the production of taraxasterol, ψ-taraxasterol, δ-amyrin, β-amyrin, and α-amyrin in transgenic tobacco overexpressing the T. coreanum TcOSC1 gene. Transgenic tobacco plants were obtained via Agrobacterium tumefaciens-mediated transformation. The introduction and expression of transgenic genes in tobacco was confirmed by genomic PCR and qRT–PCR, respectively. All lines of transgenic tobacco produced five new triterpenes, namely, taraxasterol, ψ-taraxasterol, δ-amyrin, β-amyrin, and α-amyrin, but not dammarenediol-II. The accumulation of phytosterols (β-sitosterol, campesterol, and stigmasterol) was reduced in transgenic tobacco compared to the wild-type control. Triterpene accumulation in transgenic tobacco plants was different among leaf, stem, and root. The highest level of triterpenes (617 µg g−1 dry weight) were observed in leaf of Tr4 transgenic line. Conclusively, we established the production of multiple triterpenes in transgenic tobacco by overexpress- ing the TcOSC1 gene, which can be applied in the production of triterpenes for utilization as a source of pharmacologically active materials.