title: Characterisation of two oxidosqualene cyclases responsible for triterpenoid biosynthesis in Ilex asprella.
abstract: Ilex asprella, a plant widely used as a folk herbal drug in southern China, produces and stores a large amount of triterpenoid saponins, most of which are of the α-amyrin type. In this study, two oxidosqualene cyclase (OSC) cDNAs, IaAS1 and IaAS2, were cloned from the I. asprella root. Functional characterisation was performed by heterologous expression in the yeast Saccharomyces cerevisiae. Analysis of the resulting products by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) showed that both genes encode a mixed amyrin synthase, producing α-amyrin and β-amyrin at different ratios. IaAS1, which mainly produces α-amyrin, is the second triterpene synthase so far identified in which the level of α-amyrin produced is ≥80% of total amyrin production. By contrast, IaAS2 mainly synthesises β-amyrin, with a yield of 95%. Gene expression patterns of these two amyrin synthases in roots and leaves of I. asprella were found to be consistent with the content patterns of total saponins. Finally, phylogenetic analysis and multiple sequence alignment of the two amyrin synthases against several known OSCs from other plants were conducted to further elucidate their evolutionary relationship.
authors: Research Center of Chinese Herbal Resource Science and Engineering, Key Laboratory of Chinese Medicinal Resource from Lingnan, Guangzhou University of Chinese Medicine, Guangzhou 510006, China. zheng.x.s1987@163.com.|The Key Laboratory of Technology of Breaking Cell Wall and Application in Chinese Medicine Decoction Pieces, Zhongshan Zhongzhi Pharmaceutical Group, Zhongshan 528437, China. zheng.x.s1987@163.com.
authors: Xiasheng
authors: X
authors: Zheng
authors: Research Center of Chinese Herbal Resource Science and Engineering, Key Laboratory of Chinese Medicinal Resource from Lingnan, Guangzhou University of Chinese Medicine, Guangzhou 510006, China. lxx.carrot@163.com.
authors: Xiuxiu
authors: X
authors: Luo
authors: Research Center of Chinese Herbal Resource Science and Engineering, Key Laboratory of Chinese Medicinal Resource from Lingnan, Guangzhou University of Chinese Medicine, Guangzhou 510006, China. ygb900810@163.com.
authors: Guobing
authors: G
authors: Ye
authors: Research Center of Chinese Herbal Resource Science and Engineering, Key Laboratory of Chinese Medicinal Resource from Lingnan, Guangzhou University of Chinese Medicine, Guangzhou 510006, China. yavechan@163.com.
authors: Ye
authors: Y
authors: Chen
authors: Research Center of Chinese Herbal Resource Science and Engineering, Key Laboratory of Chinese Medicinal Resource from Lingnan, Guangzhou University of Chinese Medicine, Guangzhou 510006, China. xiaoyu3463@gmail.com.
authors: Xiaoyu
authors: X
authors: Ji
authors: Research Center of Chinese Herbal Resource Science and Engineering, Key Laboratory of Chinese Medicinal Resource from Lingnan, Guangzhou University of Chinese Medicine, Guangzhou 510006, China. 435892240wll@gmail.com.
authors: Lingling
authors: L
authors: Wen
authors: Research Center of Chinese Herbal Resource Science and Engineering, Key Laboratory of Chinese Medicinal Resource from Lingnan, Guangzhou University of Chinese Medicine, Guangzhou 510006, China. yaping1965@163.com.
authors: Yaping
authors: Y
authors: Xu
authors: Research Center of Chinese Herbal Resource Science and Engineering, Key Laboratory of Chinese Medicinal Resource from Lingnan, Guangzhou University of Chinese Medicine, Guangzhou 510006, China. zyfxsherry@gzucm.edu.cn.
authors: Hui
authors: H
authors: Xu
authors: Research Center of Chinese Herbal Resource Science and Engineering, Key Laboratory of Chinese Medicinal Resource from Lingnan, Guangzhou University of Chinese Medicine, Guangzhou 510006, China. zhanrt@gzucm.edu.cn.
authors: Ruoting
authors: R
authors: Zhan
authors: Research Center of Chinese Herbal Resource Science and Engineering, Key Laboratory of Chinese Medicinal Resource from Lingnan, Guangzhou University of Chinese Medicine, Guangzhou 510006, China. chenww@gzucm.edu.cn.
authors: Weiwen
authors: W
authors: Chen
mesh_terms: D003001:Cloning, Molecular; D019143:Evolution, Molecular; D008401:Gas Chromatography-Mass Spectrometry; D030017:Ilex / Q000737:chemistry / Q000201:enzymology*; D019751:Intramolecular Transferases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D018515:Plant Leaves / Q000737:chemistry / Q000201:enzymology; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D018517:Plant Roots / Q000737:chemistry / Q000201:enzymology; D012503:Saponins / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D012503:Saponins; D019751:Intramolecular Transferases; C021924:lanosterol synthase