[Cloning and expression of SmDXS2 gene in Swertia mussotii].

1-deoxy-D-xylulose-5-phosphate synthase2(DXS2) is the first key enzyme of the MEP pathway,which plays an important role in terpene biosynthesis of plants. According to the data of Swertia mussotii transcriptome, DXS2 gene(Gen Bank number MH535905) was cloned and named as Sm DXS2. The bioinformatics results showed that Sm DXS2 has no intron,with a 2 145 bp open reading frame encoding a polypeptide of 714 amino acids. They are belonging to 20 kinds of amino acids,and the most abundant amino acids include Ala,Gly and Trp. The predicted protein molecular weight was 76. 91 k Da and its theoretical isoelectric point(p I) was6. 5,which belonging to a hydrophilic protein. α-Helix and loop were the major motifs of predicted secondary structure of DXS2. The three function domains are TPP＿superfamily,Transket＿pyr＿ superfamily and Transketolase＿C superfamily,respectively. The Sm DXS2 protein shared high identity with other DXS2 proteins of plants. Phylogenetic analysis showed that Sm DXS2 protein is grouped with the gentian DXS2 protein. The recombinant protein of Sm DXS2 gene in Escherichia coli was approximately 92. 00 k Da(containing sumo-His tag protein 13 k Da),which was consistent with the anticipated size.This work will provide a foundation for further functional research of Sm DXS2 protein and increasing the product of iridoid compound by genetic engineering in S. mussotii.

Cloning and Characterization of Two Iridoid Synthase Homologs from Swertia Mussotii.

Swertia mussotii is an important medicinal plant found on the Qinghai Tibetan Plateau that has great economic and medicinal value. This plant has enjoyed a long history of use as a curative for hepatitis. The biological activity of secoiridoids, including gentiopicroside and swertiamarin, has been mainly tested for its anti-hepatitis effects. Here, we identify two candidate genes (SmIS1 and SmIS2) that are homologues of iridoid synthase and that are components of the secoiridoid pathway in S. mussotii. Using sequencing and phylogenetic analyses, we confirm that SmIS1 and SmIS2 contain six conserved short-chain dehydrogenases/reductase (SDR) motifs and thus belong to the P5ßRs group. The two purified Escherichia coli-expressed proteins reduced 8-oxogeranial to both nepetalactol and iridodials. A comparison of the kinetic parameters of SmIS1 and SmIS2 recombinant proteins revealed that SmIS2 has a lower affinity than SmIS1 for 8-oxogeranial. Transcript levels of the two genes were analysed in three different tissues of S. mussotii using semi-quantitative RT-PCR and RT-qPCR. SmIS1 and SmIS2 expression levels were more abundant in leaves and stems. This investigation adds to our knowledge of P5ßRs genes in the secoiridoid synthesis pathway and provides candidate genes for genetically improving S. mussotii by enhancing secondary metabolite production.

Cloning and functional analysis of geraniol 10-hydroxylase, a cytochrome P450 from Swertia mussotii Franch.

Swertia mussotii Franch has anti-hepatitis activity and contains a high level of iridoid monoterpenoids. The cytochrome P450 monooxygenase (CYP) geraniol 10-hydroxylase (G10H) is thought to play an important role in iridoid monoterpenoid and indole alkaloid biosynthesis. Here we report the isolation of a full-length cDNA clone of S. mussotii G10H (SmG10H). The predicted gene product was a 496 residue protein designated CYP76B10, the sequence of which was highly similar to that of the CYP76 family, particularly to Catharanthus roseus G10H (80.2% homology). SmG10H transcripts were much more abundant in the leaves than in either the root or the stem, and were derived from a single copy gene. SmG10H expression was upregulated by treatment with methyljasmonate (MeJA) over a period from 6 h to 36 h after treatment. Accumulation of swertiamarin increased after elicitation by MeJA. SmG10H was heterologously expressed in both Escherichia coli and Pichia pastoris (yeast), forming a 55.5-kDa protein. Based on analysis in vitro, SmG10H was found to have catalytic activity hydroxylating geraniol. In the SmG10H overexpression plants, the level of SmG10H transcript and the contents of 10-hydroxygeraniol and swertiamarin increased simultaneously.

Regulation of hazardous exposure by protective exposure: modulation of phase II detoxification and lipid peroxidation by Camellia sinensis and Swertia chirata.

Many natural compounds are now known to have a modulatory role on physiological functions and biotransformation reactions involved in the detoxification process, thereby affording protection from cytotoxic, genotoxic, and metabolic actions of environmental toxicants. As part of a programme on evaluation of food, beverage, and traditional medicinal plants for their anticarcinogenic activity, their effects on detoxification enzymes were also studied. The present report deals with Camellia sinensis and Swertia chirata. The effect of water infusions as well as crude and purified components of these plants on glutathione-S-transferase (GST), glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase (CAT) was analyzed in mice that were exposed to the chemical carcinogen DMBA. All the four enzymes were found to be activated in different degrees following treatment. The effect of Theaflavin, a component of black tea, was highly significant. The activation of the enzymes was accompanied by significant reduction in lipid peroxidation. The observation suggest the chemopreventive potential of both Camellia sinensis and Swertia chirata.