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PgLOX6 encoding a lipoxygenase contributes to jasmonic acid biosynthesis and ginsenoside production in Panax ginseng.

ABSTRACT: Ginsenosides, the valuable pharmaceutical compounds in Panax ginseng, are triterpene saponins that occur mainly in ginseng plants. It was shown that in vitro treatment with the phytohormone jasmonic acid (JA) is able to increase ginsenoside production in ginseng plants. To understand the molecular link between JA biosynthesis and ginsenoside biosynthesis, we identified a JA biosynthetic 13-lipoxygenase gene (PgLOX6) in P. ginseng that promotes ginsenoside production. The expression of PgLOX6 was high in vascular bundles, which corresponds with expression of ginsenoside biosynthetic genes. Consistent with the role of PgLOX6 in synthesizing JA and promoting ginsenoside synthesis, transgenic plants overexpressing PgLOX6 in Arabidopsis had increased amounts of JA and methyl jasmonate (MJ), increased expression of triterpene biosynthetic genes such as squalene synthase (AtSS1) and squalene epoxidase (AtSE1), and increased squalene content. Moreover, transgenic ginseng roots overexpressing PgLOX6 had around 1.4-fold increased ginsenoside content and upregulation of ginsenoside biosynthesis-related genes including PgSS1, PgSE1, and dammarenediol synthase (PgDDS), which is similar to that of treatment with MJ. However, MJ treatment of transgenic ginseng significantly enhanced JA and MJ, associated with a 2.8-fold increase of ginsenoside content compared with the non-treated, non-transgenic control plant, which was 1.4 times higher than the MJ treatment effect on non-transgenic plants. These results demonstrate that PgLOX6 is responsible for the biosynthesis of JA and promotion of the production of triterpenoid saponin through up-regulating the expression of ginsenoside biosynthetic genes. This work provides insight into the role of JA in biosynthesizing secondary metabolites and provides a molecular tool for increasing ginsenoside production.

SUBMITTER: Rahimi S

PROVIDER: S-EPMC5100016 | biostudies-literature | 2016 Nov

REPOSITORIES: biostudies-literature

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PgLOX6 encoding a lipoxygenase contributes to jasmonic acid biosynthesis and ginsenoside production in Panax ginseng.

Rahimi Shadi S Kim Yu-Jin YJ Sukweenadhi Johan J Zhang Dabing D Yang Deok-Chun DC

Journal of experimental botany 20161006 21

Ginsenosides, the valuable pharmaceutical compounds in Panax ginseng, are triterpene saponins that occur mainly in ginseng plants. It was shown that in vitro treatment with the phytohormone jasmonic acid (JA) is able to increase ginsenoside production in ginseng plants. To understand the molecular link between JA biosynthesis and ginsenoside biosynthesis, we identified a JA biosynthetic 13-lipoxygenase gene (PgLOX6) in P. ginseng that promotes ginsenoside production. The expression of PgLOX6 was ...[more]

PMID: 27811076

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Project description:BackgroundPanax ginseng C. A. Mey is one of famous medicinal herb plant species. Its major bioactive compounds are various ginsenosides in roots and rhizomes. It is commonly accepted that ginsenosides are synthesized from terpene precursors, IPP and DMAPP, through the cytoplasmic mevalonate (MVA) pathway. Another plastic 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway was proved also contributing to ginsenoside generation in the roots of P. ginseng by using specific chemical inhibitors recently. But their gene expression characteristics are still under reveal in P. ginseng. With the development of the high-throughput next generation sequencing (NGS) technologies, we have opportunities to discover more about the complex ginsenoside biosynthesis pathways in P. ginseng.ResultsWe carried out deep RNA sequencing and comprehensive analyses on the ginseng root samples of 1-5 years old and five different tissues of 5 years old ginseng plants. The de novo assembly totally generated 48,165 unigenes, including 380 genes related to ginsenoside biosynthesis and all the genes encoding the enzymes of the MEP pathway and the MVA pathway. We further illustrated the gene expression profiles related to ginsenoside biosynthesis among 1-5 year-old roots and different tissues of 5 year-old ginseng plants. Particularly for the first time, we revealed that the gene transcript abundances of the MEP pathway were similar to those of the MVA pathway in ginseng roots but higher in ginseng leaves. The IspD was predicated to be the rate-limiting enzyme in the MEP pathway through both co-expression network and gene expression profile analyses.ConclusionsAt the transcriptional level, the MEP pathway has similar contribution to ginsenoside biosynthesis in ginseng roots, but much higher in ginseng leaves, compared with the MVA pathway. The IspD might be the key enzyme for ginsenoside generation through the MEP pathway. These results provide new information for further synthetic biology study on ginsenoside metabolic regulation.

Project description:Panax ginseng C.A. Meyer is a precious Chinese herbal medicine belonging to the Araliaceae family. Because ginseng is extremely taboo, it seriously restricts the sustainable development of the ginseng industry. The allelopathic effect of triterpenoid saponins is one of the important incentives for continuous cropping disorders. However, there are few studies on the mechanism of allelopathic autotoxicity of triterpenoid ginsenosides. Therefore, this study took ginseng hairy roots as the research object, exogenously added ginsenoside Ro to regulate the growth of hairy roots, and measured the changes in its physiological and saponin content. It was found that ginseng hairy roots grew significantly under Ro-0.5 mg/L stress. Inhibition, the specificity of root tip cell injury was obvious, promoted the accumulation of endogenous hormones IAA and SA, and inhibited the accumulation of ABA and JA. The accumulation of ginsenosides was significantly inhibited (except Rg3) under Ro-0.5 mg/L stress. The mRNA analysis of the Ro-0.5 mg/L group and CK group showed that the differentially expressed genes were mostly concentrated in the hormone signal transduction pathway. The genes ARF7 and EFM were up-regulated, and XTH23 and ZOX1 were down-regulated, which can be used as important candidates for hormone-responsive continuous cropping disorders. Gene. 74 differentially expressed miRNAs were identified based on miRNA sequencing, of which 22 were up-regulated and 52 were down-regulated. The target genes of ptc-miR156k_L+1, mtr-miR156b-5p, gma-miR156a_R+1, and mtr-miR156e were all TRINITY_DN14567_c0_g4, TRINITY_DN14567_c0_g4 is a gene in the plant hormone signal transduction pathway, and the four miRNAs are all negatively correlated with mRNA, indicating that ptc-miR156k_L+1, mtr-miR156b-5p, gma-miR156a_R+1, and mtr-miR156e are very likely involved in ginseng Response to continuous cropping disorders and regulation of ginsenoside synthesis. Our findings will provide a useful platform for unraveling the continuous cropping barrier of ginseng and new insights into the genetic engineering of plant stress responses.

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PgLOX6 encoding a lipoxygenase contributes to jasmonic acid biosynthesis and ginsenoside production in Panax ginseng.

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PgLOX6 encoding a lipoxygenase contributes to jasmonic acid biosynthesis and ginsenoside production in Panax ginseng.

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