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Transcriptomic profiling reveals MEP pathway contributing to ginsenoside biosynthesis in Panax ginseng.

ABSTRACT: BACKGROUND:Panax 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. RESULTS:We 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. CONCLUSIONS:At 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.

SUBMITTER: Xue L

PROVIDER: S-EPMC6524269 | biostudies-literature | 2019 May

REPOSITORIES: biostudies-literature

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Transcriptomic profiling reveals MEP pathway contributing to ginsenoside biosynthesis in Panax ginseng.

Xue Le L He Zilong Z Bi Xiaochun X Xu Wei W Wei Ting T Wu Shuangxiu S Hu Songnian S

BMC genomics 20190517 1

<h4>Background</h4>Panax 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 inhibitor ...[more]

PMID: 31101014

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Project description:Panax ginseng C.A. Meyer is a shade plant, and its leaves are an important medicinal part of P. ginseng. Light intensity plays a crucial role in physiological activities and metabolite accumulation in P. ginseng. Currently, little is known about the molecular mechanisms underlying physiological changes and quality under different light intensities in P. ginseng leaves. Therefore, we investigated the changes in photosynthetic physiology, secondary metabolism, transcriptomics, and metabolomics of P. ginseng leaves under different light intensities [T20 (20 µmol m-2·s-1), T50 (50 µmol m-2·s-1), T100 (100 μmol m-2·s-1)]]. Higher light intensity positively influenced the yield, photosynthesis, and accumulation of polysaccharides, soluble sugars, terpenoids, and ginsenosides in P. ginseng leaves. The T100 treatment notably promoted the accumulation of ginsenosides in the leaves, resulting in a 68.32% and 45.55% increase in total ginsenosides compared to the T20 and T50 treatments, respectively. Ginsenosides Rg1, Re, Rb1, Rc, Rg2, Rb2, Rb3, and Rd were 1.28-, 1.47-, 2.32-, 1.64-, 1.28-, 2.59-, 1.66-, and 2.28-times higher than in the T20 treatment. Furthermore, 285 differentially accumulated metabolites (DAMs) and 4218 differentially expressed genes (DEGs) in the metabolome and transcriptome of P. ginseng leaves, respectively, were identified. 13 triterpenoid saponins were significantly upregulated, and three were downregulated. The expression of genes encoding photosystem II reaction center proteins was upregulated under the T100 treatment, thereby increasing photosynthetic activity. The T100 treatment enhanced the expression of genes involved in photosynthetic carbon and energy metabolism in P. ginseng. The expression of antenna protein synthesis genes was upregulated under the T20, which increased the ability to capture light in P. ginseng leaves. T100 upregulated the expression of HMGR, SS, CYP716A53v2, UGT74AE, PgUGT1, and UGTPg45, thereby promoting terpene and ginsenoside synthesis. In summary, 100 µmol m-2·s-1 was conducive to quality formation of P. ginseng leaves. This study elucidates molecular mechanisms underlying the photosynthetic physiology and ginsenoside synthesis in P. ginseng under varying light intensities and provides a theoretical basis for the P. ginseng cultivation and its industrial production of secondary metabolites.

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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Transcriptomic profiling reveals MEP pathway contributing to ginsenoside biosynthesis in Panax ginseng.

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Transcriptomic profiling reveals MEP pathway contributing to ginsenoside biosynthesis in Panax ginseng.

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