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

ABSTRACT: 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 P5βRs 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 P5βRs genes in the secoiridoid synthesis pathway and provides candidate genes for genetically improving S. mussotii by enhancing secondary metabolite production.

SUBMITTER: Xiang B

PROVIDER: S-EPMC6152284 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Swertia mussotii

Project description:Swertia mussotii Genome sequencing

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Introgression of Swertia mussotii gene into Bupleurum scorzonerifolium via somatic hybridization.

Project description:BackgroundThe wild herb Swertia mussotii is a source of the anti-hepatitis compounds swertiamarin, mangiferin and gentiopicroside. Its over-exploitation has raised the priority of producing these compounds heterologously. Somatic hybridization represents a novel approach for introgressing Swertia mussotii genes into a less endangered species.ResultsProtoplasts derived from calli of Bupleurum scorzonerifolium and S. mussotii were fused to produce 194 putative hybrid cell lines, of which three (all derived from fusions where the S. mussotii protoplasts were pre-treated for 30 s with UV light) later differentiated into green plants. The hybridity of the calli was confirmed by a combination of isozyme, RAPD and chromosomal analysis. The hybrid calli genomes were predominantly B. scorzonerifolium. GISH analysis of mitotic chromosomes confirmed that the irradiation of donor protoplasts increased the frequency of chromosome elimination and fragmentation. RFLP analysis of organellar DNA revealed that mitochondrial and chloroplast DNA of both parents coexisted and recombined in some hybrid cell lines. Some of the hybrid calli contained SmG10H from donor, and produced swertiamarin, mangiferin and certain volatile compounds characteristic of S. mussotii. The expression of SmG10H (geraniol 10-hydroxylase) was associated with the heterologous accumulation of swertiamarin.ConclusionsSomatic hybrids between B. scorzonerifolium and S. mussotii were obtained, hybrids selected all contained introgressed nuclear and cytoplasmic DNA from S. mussotii; and some produced more mangiferin than the donor itself. The introgression of SmG10H was necessary for the accumulation of swertiamarin.

| S-EPMC3098146 | biostudies-literature

Swertianlarin, isolated from Swertia mussotii Franch, increases detoxification enzymes and efflux transporters expression in rats.

Project description:Swertianlarin, isolated from Swertia mussotii Franch and Enicostemma axillare, has hepatoprotective effects against cholestasis in rat models of hepatotoxicity. However, the underlying molecular mechanism is not clear. We then treated rats with swertianlarin for 7 d and then measured serum liver injury markers, lipids, and bile salts, as well as the expression of bile acid synthesis and detoxification enzymes (e.g. Cyp7a1 and Cyp3a), membrane influx and efflux transporters (e.g. Ntcp and Mrp3), nuclear receptors (e.g. Pxr and Fxr/Shp) and transcriptional factors (e.g. Nrf2 and Hnf3?) in the liver. We found a significant induction of the expression of the basolateral efflux transporters Mrp3 and Mrp4 and canalicular transporter Mdr1 in rats treated with swertianlarin, compared with the controls (1.9-fold and 2.2-fold, P < 0.005, and 3.4-fold, P < 0.05, respectively). The expression of detoxification enzymes Cyp3a, Ugt2b, Sult2a1 and Gsta1 in rats treated with swertianlarin was significantly higher than that in controls (3.7-fold, 2.8-fold, 2.1-fold, and 1.7-fold, respectively, all P < 0.05). Expression of the synthetic enzyme, Cyp8b1, was higher in rats treated with swertianlarin than that in controls (1.8-fold at mRNA level and 3.4-flod at protein level, P < 0.05). Elevated serum levels of the conjugated bile acids, taurocholic acid and taurodeoxycholic acid, and a reduction in levels of serum ALP, unconjugated bile acid ?MCA, and TG were observed (all P < 0.05). In conclusion, swertianlarin significantly up-regulates hepatic bile acid detoxification enzymes and efflux transporters in rats, which can increase the water solubility of hydrophobic bile acids and elimination of conjugated bile acids.

| S-EPMC4348896 | biostudies-literature

The Complete Chloroplast Genome Sequence of the Medicinal Plant Swertia mussotii Using the PacBio RS II Platform.

Project description:Swertia mussotii is an important medicinal plant that has great economic and medicinal value and is found on the Qinghai Tibetan Plateau. The complete chloroplast (cp) genome of S. mussotii is 153,431 bp in size, with a pair of inverted repeat (IR) regions of 25,761 bp each that separate an large single-copy (LSC) region of 83,567 bp and an a small single-copy (SSC) region of 18,342 bp. The S. mussotii cp genome encodes 84 protein-coding genes, 37 transfer RNA (tRNA) genes, and eight ribosomal RNA (rRNA) genes. The identity, number, and GC content of S. mussotii cp genes were similar to those in the genomes of other Gentianales species. Via analysis of the repeat structure, 11 forward repeats, eight palindromic repeats, and one reverse repeat were detected in the S. mussotii cp genome. There are 45 SSRs in the S. mussotii cp genome, the majority of which are mononucleotides found in all other Gentianales species. An entire cp genome comparison study of S. mussotii and two other species in Gentianaceae was conducted. The complete cp genome sequence provides intragenic information for the cp genetic engineering of this medicinal plant.

| S-EPMC6274542 | biostudies-literature

Deep sequencing and transcriptome analyses to identify genes involved in secoiridoid biosynthesis in the Tibetan medicinal plant Swertia mussotii.

Project description:Swertia mussotii Franch. is an important traditional Tibetan medicinal plant with pharmacological properties effective in the treatment of various ailments including hepatitis. Secoiridoids are the major bioactive compounds in S. mussotii. To better understand the secoiridoid biosynthesis pathway, we generated transcriptome sequences from the root, leaf, stem, and flower tissues, and performed de novo sequence assembly, yielding 98,613 unique transcripts with an N50 of 1,085 bp. Putative functions could be assigned to 35,029 transcripts (35.52%) based on BLAST searches against annotation databases including GO and KEGG. The expression profiles of 39 candidate transcripts encoding the key enzymes for secoiridoid biosynthesis were examined in different S. mussotii tissues, validated by qRT-PCR, and compared with the homologous genes from S. japonica, a species in the same family, unveiling the gene expression, regulation, and conservation of the pathway. The examination of the accumulated levels of three bioactive compounds, sweroside, swertiamarin, and gentiopicroside, revealed their considerable variations in different tissues, with no significant correlation with the expression profiles of key genes in the pathway, suggesting complex biological behaviours in the coordination of metabolite biosynthesis and accumulation. The genomic dataset and analyses presented here lay the foundation for further research on this important medicinal plant.

| S-EPMC5320516 | biostudies-literature

Inverted stereocontrol of iridoid synthase in snapdragon.

Project description:The natural product class of iridoids, found in various species of flowering plants, harbors astonishing chemical complexity. The discovery of iridoid biosynthetic genes in the medicinal plant Catharanthus roseus has provided insight into the biosynthetic origins of this class of natural product. However, not all iridoids share the exact five- to six-bicyclic ring scaffold of the Catharanthus iridoids. For instance, iridoids in the ornamental flower snapdragon (Antirrhinum majus, Plantaginaceae family) are derived from the C7 epimer of this scaffold. Here we have cloned and characterized the iridoid synthase enzyme from A. majus (AmISY), the enzyme that is responsible for converting 8-oxogeranial into the bicyclic iridoid scaffold in a two-step reduction-cyclization sequence. Chiral analysis of the reaction products reveals that AmISY reduces C7 to generate the opposite stereoconfiguration in comparison with the Catharanthus homologue CrISY. The catalytic activity of AmISY thus explains the biosynthesis of 7-epi-iridoids in Antirrhinum and related genera. However, although the stereoselectivity of the reduction step catalyzed by AmISY is clear, in both AmISY and CrISY, the cyclization step produces a diastereomeric mixture. Although the reduction of 8-oxogeranial is clearly enzymatically catalyzed, the cyclization step appears to be subject to less stringent enzyme control.

| S-EPMC5582856 | biostudies-literature

Oral administration of oleanolic acid, isolated from Swertia mussotii Franch, attenuates liver injury, inflammation, and cholestasis in bile duct-ligated rats.

Project description:BACKGROUND & AIMS:Oleanolic acid is abundantly distributed in Swertia mussotii Franch, a Chinese traditional herb for the treatment of jaundice. However, the hepatoprotective role of oleanolic acid in obstructive cholestasis and its underlying molecular mechanism are unclear. METHODS:Normal rats and bile duct-ligated (BDL) rats were given oleanolic acid and serum biochemistry, bile salts, and pro-inflammatory factors were measured, as well as the expression levels of liver bile acid synthesis and detoxification enzymes, membrane transporters, nuclear receptors, and transcriptional factors. RESULTS:Oral administration of oleanolic acid at 100 mg/kg did not cause rat liver injury. However, it significantly reduced the serum levels of alanine aminotransferase (ALT) on days 7 and 14, aspartate aminotransferase (AST) and TNF-? on day 14, and alkaline phosphatase (ALP) and IL-1? on days 3, 7, and 14 in the BDL rats. Furthermore, the serum levels of total bile acid (TBA) and bile acids, including CDCA, CA, DCA, and T?/?MCA were significantly reduced by oleanolic acid on day 3 in the BDL rats. In addition, the expression levels of detoxification enzymes Cyp3a, Ugt2b, Sult2a1, Gsta1-2, and Gstm1-3, membrane transporters Mrp3, Mrp4, Ost?, Mdr1, Mdr2, and Bsep, nuclear receptors Pxr, Vdr, Hnf4?, Rxr?, Rar?, Lxr, and Lrh-1, and transcriptional factors Nrf2, Hnf3?, and Ahr were significantly increased in oleanolic acid-treated rats. CONCLUSION:We demonstrated that the oral administration of oleanolic acid attenuates liver injury, inflammation, and cholestasis in BDL rats. The anti-cholestatic effect may be associated with the induction of hepatic detoxification enzymes and efflux transporters mediated by nuclear receptors and transcriptional factors.

| S-EPMC4402745 | biostudies-literature

Transcriptome-based identification and functional characterization of iridoid synthase involved in monotropein biosynthesis in blueberry.

Project description:Blueberries (Vaccinium spp.) are well known for their nutritional quality, and recent work has shown that Vaccinium spp. also produce iridoids, which are specialized metabolites with potent health-promoting benefits. The iridoid glycoside monotropein, which has anti-inflammatory and antinociceptive activities, has been detected in several wild blueberry species but in only a few cultivated highbush blueberry cultivars. How monotropein is produced in blueberry and the genes involved in its biosynthesis remain to be elucidated. Using a monotropein-positive (M+) and monotropein-negative (M-) cultivar of blueberry, we employed transcriptomics and comparative genomics to identify candidate genes in the blueberry iridoid biosynthetic pathway. Orthology analysis was completed using de novo transcript assemblies for both the M+ and M- blueberry cultivars along with the known iridoid-producing plant species Catharanthus roseus to identify putative genes involved in key steps in the early iridoid biosynthetic pathway. From the identified orthologs, we functionally characterized iridoid synthase (ISY), a key enzyme involved in formation of the iridoid scaffold, from both the M+ and M- cultivars. Detection of nepetalactol suggests that ISY from both the M+ and M- cultivars produce functional enzymes that catalyze the formation of iridoids. Transcript accumulation of the putative ISY gene did not correlate with monotropein production, suggesting other genes in the monotropein biosynthetic pathway may be more directly responsible for differential accumulation of the metabolite in blueberry. Mutual rank analysis revealed that ISY is co-expressed with UDP-glucuronosyltransferase, which encodes an enzyme downstream of the ISY step. Results from this study contribute new knowledge in our understanding of iridoid biosynthesis in blueberry and could lead to development of new cultivars with increased human health benefits.

| S-EPMC10333835 | biostudies-literature

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