title: Molecular characterization, expression, and regulation of Gynostemma pentaphyllum squalene epoxidase gene 1.
abstract: Gynostemma pentaphyllum (Thunb.) Makino is a perennial medicinal herb widely distributed in China. This herb contains important medicinal components called gypenosides, which belong to dammarane-type triterpenoid saponins. Squalene epoxidase (SE, EC 1.14.99.7) catalyzes the epoxidation of squalene to form oxidosqualene and is a key regulatory enzyme in triterpenoid saponin biosynthesis. In this study, a SE gene designated as GpSE1 was isolated from G. pentaphyllum leaves. The deduced protein sequence of GpSE1 contained two conserved domains involved in the catalytic function of SE. GpSE1 was expressed as inclusion bodies in Escherichia coli cells, and the HIS-tagged recombinant protein was successfully purified and renatured in vitro. Immunofluorescence indicated that the polygonal reticular fluorescence signal of GpSE1 was significantly stronger in young leaves than in mature leaves and rhizomes. This finding is consistent with the tissue-specific expression pattern of GpSE1 and suggests that the young leaves of G. pentaphyllum mainly serve as the active site of gypenoside synthesis. Methyl jasmonate (MeJA) treatment upregulated GpSE1 expression in both the young and mature leaves of G. pentaphyllum, with greater upregulation in young leaves than in mature leaves. However, the expression of GpSE1 was not enhanced continually with the increase in MeJA concentration. Moreover, the GpSE1 expression was maximally regulated in response to 50 μM MeJA but not to 100 μM MeJA. This result indicates that MeJA exerts a concentration-dependent effect on GpSE1 expression.
authors.affiliation: College of Biological Sciences and Biotechnology, National Engineering Laboratory for Tree Breeding, Beijing Forestry University, Beijing 100083, China. Electronic address: guohh@bjfu.edu.cn.
authors.forename: Huihong
authors.initials: H
authors.lastname: Guo
authors.affiliation: College of Biological Sciences and Biotechnology, National Engineering Laboratory for Tree Breeding, Beijing Forestry University, Beijing 100083, China. Electronic address: lirf13@163.com.
authors.forename: Rufang
authors.initials: R
authors.lastname: Li
authors.affiliation: College of Biology and Environmental Sciences, Jishou University, Jishou 416000, China. Electronic address: liushibiao_1@163.com.
authors.forename: Shibiao
authors.initials: S
authors.lastname: Liu
authors.affiliation: College of Biological Sciences and Biotechnology, National Engineering Laboratory for Tree Breeding, Beijing Forestry University, Beijing 100083, China. Electronic address: momozhaona@163.com.
authors.forename: Na
authors.initials: N
authors.lastname: Zhao
authors.affiliation: College of Biological Sciences and Biotechnology, National Engineering Laboratory for Tree Breeding, Beijing Forestry University, Beijing 100083, China. Electronic address: hanhan@bjfu.edu.cn.
authors.forename: Shuo
authors.initials: S
authors.lastname: Han
authors.affiliation: College of Biological Sciences and Biotechnology, National Engineering Laboratory for Tree Breeding, Beijing Forestry University, Beijing 100083, China. Electronic address: lemon@bjfu.edu.cn.
authors.forename: Mengmeng
authors.initials: M
authors.lastname: Lu
authors.affiliation: College of Biological Sciences and Biotechnology, National Engineering Laboratory for Tree Breeding, Beijing Forestry University, Beijing 100083, China. Electronic address: liuxiaomin04@163.com.
authors.forename: Xiaomin
authors.initials: X
authors.lastname: Liu
authors.affiliation: College of Biological Sciences and Biotechnology, National Engineering Laboratory for Tree Breeding, Beijing Forestry University, Beijing 100083, China.
authors.forename: Xinli
authors.initials: X
authors.lastname: Xia
mesh_terms: D000085:Acetates / Q000494:pharmacology; D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D003517:Cyclopentanes / Q000494:pharmacology; D004926:Escherichia coli / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D029774:Gynostemma / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics*; D054883:Oxylipins / Q000494:pharmacology; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D010946:Plants, Medicinal / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D050603:Squalene Monooxygenase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*
chemical_list: D000085:Acetates; D003517:Cyclopentanes; D054883:Oxylipins; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; C072239:methyl jasmonate; D050603:Squalene Monooxygenase
keywords: Expression regulation; Gene expression; Gynostemma pentaphyllum; Immunofluorescence; Methyl jasmonate; Squalene epoxidase