Comparative transcriptome analysis on wild-simulated ginseng of different age revealed possible mechanism of ginsenoside accumulation.

Panax ginseng is one of the most famous pharmaceutical plants in Asia. Ginseng plants grown in mountain have longer longevity which ensures higher accumulation of ginsenoside components than those grown in farms. However, wild-simulated ginseng over certain age cannot be easily distinguished in morphology. To identify transcriptomic mechanism of ginsenoside accumulation in older wild-simulated ginseng without large phenotype change, we performed comparative transcriptome analysis for leaf, shoot, and root tissues of 7-yr-old and 13yr-old wild-simulated ginseng. Of 559 differentially expressed genes (DEGs) in comparison between 7-yr-old and 13yr-old wild-simulated ginseng, 280 leaf-, 103 shoot-, and 164 root-mainly expressing genes were found to be changed in transcript level according to age. Functional analysis revealed that pentose-phosphate shunt and abscisic acid responsive genes were up-regulated in leaf tissues of 7-yr-old ginseng while defense responsive genes were up-regulated in root tissues of 13-yr-old ginseng. Quantitative real-time PCR revealed that jasmonic acid responsive genes, ERDL6, and some UGTs were up-regulated in 13-yr-old ginseng in higher order lateral root tissues. These data suggest that bacterial stimulation in mountain region can enhance the expression of several genes which might support minor ginsenoside biosynthesis.

Key Glycosyltransferase Genes of Panax notoginseng: Identification and Engineering Yeast Construction of Rare Ginsenosides.

Panax notoginseng is one of the most famous valuable medical plants in China, and its broad application in clinical treatment has an inseparable relationship with the active molecules, ginsenosides. Ginsenosides are glycoside compounds that have varied structures for the diverse sugar chain. Although extensive work has been done, there are still unknown steps in the biosynthetic pathway of ginsenosides. Here, we screened candidate glycosyltransferase genes based on the previous genome and transcriptome data of P. notoginseng and cloned the full length of 27 UGT genes successfully. Among them, we found that PnUGT33 could catalyze different ginsenoside substrates to produce higher polarity rare ginsenosides by extending the sugar chain. We further analyzed the enzymatic kinetics and predicted the catalytic mechanism of PnUGT33 by simulating molecular docking. After that, we reconstructed the biosynthetic pathway of rare ginsenoside Rg3 and gypenoside LXXV in yeast. By combining the Golden Gate method and overexpressing the UDPG biosynthetic genes, we further improved the yield of engineering yeast strain. Finally, the shake-flask culture yield of Rg3 reached 51 mg/L and the fed-batch fermentation yield of gypenoside LXXV reached 94.5 mg/L, which was the first and highest record.

Molecular profiling of ginsenoside metabolites to identify estrogen receptor alpha activity.

20(S)-Protopanaxadiol (PPD) and 20(S)-Protopanaxatriol (PPT) are major metabolites of ginseng in humans and are considered to have estrogenic activity in cellular bioassays. In this study, we conducted in silico analyses to determine whether PPD and PPT interact with estrogen receptor alpha (ERα) and compared them with ERα agonists, partial agonists, and antagonists to identify their ERα activity. The transcriptome profile of 17ß-estradiol (E2), PPD, and PPT in MCF-7 cells expressing ERα was further compared to understand the ERα activity of ginsenoside metabolites. The results showed that PPD and PPT interacted with the 1ERE, 1GWR, and 3UUD ERα proteins in the E2 interaction model, the 3ERD protein in the diethylstilbestrol (DES) interaction model, and the 1X7R protein in the genistein (GEN) interaction model. Conversely, neither the 4PP6 protein of the interaction model with the antagonist resveratrol (RES) nor the 1ERR protein of the interaction model with the antagonist raloxifene (RAL) showed the conformation of amino acid residues. When E2, PPD, and PPT were exposed to MCF-7 cells, cell proliferation and gene expression were observed. The transcriptomic profiles of E2, PPD, and PPT were compared using a knowledge-based pathway. PPD-induced transcription profiling was similar to that of E2, and the neural transmission pathway was detected in both compounds. In contrast, PPT-induced transcription profiling displayed characteristics of gene expression associated with systemic lupus erythematosus. These results suggest that ginsenoside metabolites have ERα agonist activity and exhibit neuroprotective effects and anti-inflammatory actions. However, a meta-analysis using public microarray data showed that the mother compounds GRb1 and GRg1 of PPD and PPT showed metabolic functions in insulin signaling pathways, condensed DNA repair and cell cycle pathways, and immune response and synaptogenesis. These results suggest that the ginsenoside metabolites have potent ERα agonist activity; however, their gene expression profiles may differ from those of E2.

Identification of three groups of ginsenoside biosynthetic UDP-glycosyltransferases from Gynostemma pentaphyllum.

Ginsenosides are glycosylated dammarene-type triterpenes that have been identified in distantly related Panax ginseng and Gynostemma pentaphyllum. The phylogenetic relatedness of the ginsenoside biosynthetic genes in the two species was previously unknown. The final steps of ginsenoside biosynthesis are the glycosylations of hydroxylated triterpenes, protopanaxadiol (PPD) and protopanaxatriol (PPT), and their glycosylated forms by UDP-glycosyltransferases (UGTs). Ginsenoside biosynthetic UGTs have been identified in Panax but not in Gynostemma. Through a biochemical screening of Gynostemma UGTs (GpUGTs), we herein identified three groups of ginsenoside biosynthetic GpUGTs. These groups comprise: two GpUGTs that belong to the UGT71 family and glucosylate the C20-OH positions of PPD- and PPT-type ginsenosides; one GpUGT that belongs to the UGT74 family and glucosylates the C3-OH position of PPD-type ginsenosides; and two GpUGTs that belong to the UGT94 family and add a glucose to the C3-O-glucosides of PPD-type ginsenosides. These GpUGTs belong to the same UGT families as the ginsenoside biosynthetic Panax UGTs (PgUGTs). However, GpUGTs and PgUGTs belong to different subfamilies. Furthermore, cucumber UGTs orthologous to GpUGTs do not glucosylate ginsenosides. These results collectively suggest that, during evolution, P. ginseng and G. pentaphyllum independently opted to use the same UGT families to synthesize ginsenosides.

Ginsenoside Rh2 stimulates the production of mitochondrial reactive oxygen species and induces apoptosis of cervical cancer cells by inhibiting mitochondrial electron transfer chain complex.

Ginsenoside Rh2 (G­Rh2) is a monomeric compound that extracted from ginseng and possesses anti­cancer activities both in vitro and in vivo. Previously, we reported that G­Rh2 induces apoptosis in HeLa cervical cancer cells and that the process was related to reactive oxygen species (ROS) accumulation and mitochondrial dysfunction. However, the upstream mechanisms of G­Rh2, along with its cellular targets, remain to be elucidated. In the present study, the Cell Counting Kit­8 assay, flow cytometry and Hoechst staining revealed that G­Rh2 significantly inhibited cell viability and induced apoptosis of cervical cancer cells. However, G­Rh2 was demonstrated to be non­toxic to End1/e6e7 cells. JC­1, rhodamine 123 staining, oxidative phosphorylation and glycolysis capacity assays demonstrated that G­Rh2 exposure caused an immediate decrease in mitochondrial transmembrane potential due to its inhibition of mitochondrial oxidative phosphorylation, as well as glycolysis, both of which reduced cellular ATP production. Western blotting and electron transport chain (ETC) activity assays revealed that G­Rh2 significantly inhibited the activity of ETC complexes I, III and V. Overexpression of ETC complex III partially significantly restored mitochondrial ROS and inhibited the apoptosis of cervical cancer cells induced by G­Rh2. The predicted results of binding energy in molecular docking, confirmed that G­Rh2 was highly likely to induce mitochondrial ROS production and promote cell apoptosis by targeting the ETC complex, especially for ETC complex III. Taken together, the present results revealed the potential anti­cervical cancer activity of G­Rh2 and provide direct evidence for the contribution of impaired ETC complex activity to cervical cancer cell death.

Characteristics of RNA alternative splicing and its potential roles in ginsenoside biosynthesis in a single plant of ginseng, Panax ginseng C.A. Meyer.

RNA alternative splicing (AS) is prevalent in higher organisms and plays a paramount role in biology; therefore, it is crucial to have comprehensive knowledge on AS to understand biology. However, knowledge is limited about how AS activates in a single plant and functions in a biological process. Ginseng is one of the most widely used medicinal herbs that is abundant in a number of medicinal bioactive components, especially ginsenosides. In this study, we sequenced the transcripts of 14 organs from a 4-year-old ginseng plant and quantified their ginsenoside contents. We identified AS genes by analyzing their transcripts with the ginseng genome and verified their AS events by PCR. The plant had a total of 13,863 AS genes subjected to 30,801 AS events with five mechanisms: skipped exon, retained intron, alternative 5'splice site, alternative 3' splice site, and mutually exclusive exon. The genes that were more conserved, had more exons, and/or expressed across organs were more likely to be subjected to AS. AS genes were enriched in over 500 GO terms in the plant even though the number of AS gene-enriched GO terms varied across organs. At least 24 AS genes were found to be involved in ginsenoside biosynthesis. These AS genes were significantly up-enriched and more likely to form a co-expression network, thus suggesting the functions of AS and correlations of the AS genes in the process. This study provides comprehensive insights into the molecular characteristics and biological functions of AS in a single plant; thus, helping better understand biology.

Integrative transcriptome analysis identifies new oxidosqualene cyclase genes involved in ginsenoside biosynthesis in Jilin ginseng.

BACKGROUND: Jilin ginseng, Panax ginseng, is a valuable medicinal herb whose ginsenosides are its major bioactive components. The ginseng oxidosqualene cyclase (PgOSC) gene family is known to play important roles in ginsenoside biosynthesis, but few members of the gene family have been functionally studied. METHODS: The PgOSC gene family has been studied by an integrated analysis of gene expression-ginsenoside content correlation, gene mutation-ginsenoside content association and gene co-expression network, followed by functional analysis through gene regulation. RESULTS: We found that five of the genes in the PgOSC gene family, including two published ginsenoside biosynthesis genes and three new genes, were involved in ginsenoside biosynthesis. Not only were the expressions of these genes significantly correlated with ginsenoside contents, but also their nucleotide mutations significantly influenced ginsenoside contents. These results were further verified by regulation analysis of the genes by methyl jasmonate (MeJA) in ginseng hairy roots. Four of these five PgOSC genes were mapped to the ginsenoside biosynthesis pathway. These PgOSC genes expressed differently across tissues, but relatively consistent across developmental stages. These PgOSC genes formed a single co-expression network with those published ginsenoside biosynthesis genes, further confirming their roles in ginsenoside biosynthesis. When the network varied, ginsenoside biosynthesis was significantly influenced, thus revealing the molecular mechanism of ginsenoside biosynthesis. CONCLUSION: At least five of the PgOSC genes, including the three newly identified and two published PgOSC genes, are involved in ginsenoside biosynthesis. These results provide gene resources and knowledge essential for enhanced research and applications of ginsenoside biosynthesis in ginseng.

The chromosome-level reference genome assembly for Panax notoginseng and insights into ginsenoside biosynthesis.

Panax notoginseng, a perennial herb of the genus Panax in the family Araliaceae, has played an important role in clinical treatment in China for thousands of years because of its extensive pharmacological effects. Here, we report a high-quality reference genome of P. notoginseng, with a genome size up to 2.66 Gb and a contig N50 of 1.12 Mb, produced with third-generation PacBio sequencing technology. This is the first chromosome-level genome assembly for the genus Panax. Through genome evolution analysis, we explored phylogenetic and whole-genome duplication events and examined their impact on saponin biosynthesis. We performed a detailed transcriptional analysis of P. notoginseng and explored gene-level mechanisms that regulate the formation of characteristic tubercles. Next, we studied the biosynthesis and regulation of saponins at temporal and spatial levels. We combined multi-omics data to identify genes that encode key enzymes in the P. notoginseng terpenoid biosynthetic pathway. Finally, we identified five glycosyltransferase genes whose products catalyzed the formation of different ginsenosides in P. notoginseng. The genetic information obtained in this study provides a resource for further exploration of the growth characteristics, cultivation, breeding, and saponin biosynthesis of P. notoginseng.

Ginseng Omics for Ginsenoside Biosynthesis.

Ginseng, also known as the king of herbs, has been regarded as an important traditional medicine for several millennia. Ginsenosides, a group of triterpenoid saponins, have been characterized as bioactive compounds of ginseng. The complexity of ginsenosides hindered ginseng research and development both in cultivation and clinical research. Therefore, deciphering the ginsenoside biosynthesis pathway has been a focus of interest for researchers worldwide. The new emergence of biological research tools consisting of omics and bioinformatic tools or computational biology tools are the research trend in the new century. Ginseng is one of the main subjects analyzed using these new quantification tools, including tools of genomics, transcriptomics, and proteomics. Here, we review the current progress of ginseng omics research and provide results for the ginsenoside biosynthesis pathway. Organization and expression of the entire pathway, including the upstream MVA pathway, the cyclization of ginsenoside precursors, and the glycosylation process, are illustrated. Regulatory gene families such as transcriptional factors and transporters are also discussed in this review.

SMRT- and Illumina-based RNA-seq analyses unveil the ginsinoside biosynthesis and transcriptomic complexity in Panax notoginseng.

Panax notoginseng is one of the most widely used traditional Chinese herbs with particularly valued roots. Triterpenoid saponins are mainly specialized secondary metabolites, which medically act as bioactive components. Knowledge of the ginsenoside biosynthesis in P. notoginseng, which is of great importance in the industrial biosynthesis and genetic breeding program, remains largely undetermined. Here we combined single molecular real time (SMRT) and Second-Generation Sequencing (SGS) technologies to generate a widespread transcriptome atlas of P. notoginseng. We mapped 2,383 full-length non-chimeric (FLNC) reads to adjacently annotated genes, corrected 1,925 mis-annotated genes and merged into 927 new genes. We identified 8,111 novel transcript isoforms that have improved the annotation of the current genome assembly, of which we found 2,664 novel lncRNAs. We characterized more alternative splicing (AS) events from SMRT reads (20,015 AS in 6,324 genes) than Illumina reads (18,498 AS in 9,550 genes), which contained a number of AS events associated with the ginsenoside biosynthesis. The comprehensive transcriptome landscape reveals that the ginsenoside biosynthesis predominantly occurs in flowers compared to leaves and roots, substantiated by levels of gene expression, which is supported by tissue-specific abundance of isoforms in flowers compared to roots and rhizomes. Comparative metabolic analyses further show that a total of 17 characteristic ginsenosides increasingly accumulated, and roots contained the most ginsenosides with variable contents, which are extraordinarily abundant in roots of the three-year old plants. We observed that roots were rich in protopanaxatriol- and protopanaxadiol-type saponins, whereas protopanaxadiol-type saponins predominated in aerial parts (leaves, stems and flowers). The obtained results will greatly enhance our understanding about the ginsenoside biosynthetic machinery in the genus Panax.

Enzymatic Biotransformation of Ginsenoside Rb2 into Rd by Recombinant α-L-Arabinopyranosidase from Blastococcus saxobsidens.

In this study, we used a novel α-L-arabinopyranosidase (AbpBs) obtained from ginsenoside-converting Blastococcus saxobsidens that was cloned and expressed in Escherichia coli BL21 (DE3), and then applied it in the biotransformation of ginsenoside Rb2 into Rd. The gene, termed AbpBs, consisting of 2,406 nucleotides (801 amino acid residues), and with a predicted translated protein molecular mass of 86.4 kDa, was cloned into a pGEX4T-1 vector. A BLAST search using the AbpBs amino acid sequence revealed significant homology with a family 2 glycoside hydrolase (GH2). The over-expressed recombinant AbpBs in Escherichia coli BL21 (DE3) catalyzed the hydrolysis of the arabinopyranose moiety attached to the C-20 position of ginsenoside Rb2 under optimal conditions (pH 7.0 and 40°;C). Kinetic parameters for α-Larabinopyranosidase showed apparent Km and Vmax values of 0.078 ± 0.0002 micrometer and 1.4 ± 0.1 µmol/min/mg of protein against p-nitrophenyl-α-L-arabinopyranoside. Using a purified AbpBs (1 µg/ml), 0.1% of ginsenoside Rb2 was completely converted to ginsenoside Rd within 1 h. The recombinant AbpBs could be useful for high-yield, rapid, and low-cost preparation of ginsenoside Rd from Rb2.

Comparative transcriptome analysis of rhizome nodes and internodes in Panax. japonicus var. major reveals candidate genes involved in the biosynthesis of triterpenoid saponins.

The rhizome of P. japonicus var. major, one of the important herbs in Traditional Chinese medicine (TCM), has been used as tonic and hemostatic drugs in Tujia and Miao ethnic groups of China for thousand years. In this study, comparative metabolite and transcriptome analysis of rhizome nodes and internodes of wild P. japonicus var. major was performed to reveal their different roles in the biosynthesis of triterpene saponins. The results showed that the node was the crucial section for the synthesis of ginsenosides in the rhizome. The content of oleanane-type ginsenosides in the node was much higher than those in the internode. Most isoprenoid biosynthesis-related genes were highly expressed in the node. And, candidate UDP-glycosyltransferase (UGT) genes were also found to be differentially expressed between node and internode. Our study will provide a better understanding of the metabolism of ginsenosides in the rhizome of P. japonicus var. major.

Biological Synthesis of Ginsenoside Rd Using Paenibacillus horti sp. nov. Isolated from Vegetable Garden.

A Gram-stain positive, aerobic, motile, rod-shaped, and ginsenoside Rd producing novel bacterial strain, designated as MAH-16T, was isolated from soil sample of a vegetable garden and was characterized by using a polyphasic approach. The colonies were beige color, smooth, circular, and 0.3-0.7 mm in diameter when grown on tryptone soya agar for 3 days. Strain MAH-16T can grow at 20-40 °C temperature, at pH 5.0-7.0 and at 0-1% NaCl. Cell growth occurs on nutrient agar, R2A agar, tryptone soya agar, and Luria-Bertani agar but not on MacConkey agar. The strain was positive for both catalase and oxidase test. The novel strain rapidly synthesized ginsenoside Rd from major ginsenoside Rb1. According to the 16S rRNA gene sequence comparisons, the isolate was identified as a member of the genus Paenibacillus and was most closely related to Paenibacillus barengoltzii SAFN-016T (97.1%), Paenibacillus faecis 656.84T (96.7%), and Paenibacillus konsidensis LBYT (96.2%). In DNA-DNA hybridization tests, the DNA relatedness between strain MAH-16T and its closest phylogenetic neighbor was below 45.0%. The genomic DNA G + C content of isolated strain was determined to be 52.0 mol% and the predominant isoprenoid quinine was menaquinone-7 (MK-7). The major fatty acids were identified as anteiso-C15:0. The genetic characteristics in combination with chemotaxonomic and physiological data demonstrated that strain MAH-16T represented a novel species within the genus Paenibacillus, for which the name Paenibacillus horti sp. nov. is proposed, with MAH-16T as the type strain (=KACC 19299T = CGMCC1.16487T).

Notoginsenoside R1 Promotes the Growth of Neonatal Rat Cortical Neurons via the Wnt/ß-catenin Signaling Pathway.

BACKGROUND & OBJECTIVE: Notoginsenoside R1 (NGR1) is one of the main effective components of Panax notoginseng. METHOD: Primary cortical neurons were harvested from neonatal rats and cultured to analyze the role of NGR1 in neuronal growth and the effects of NGR1 on the Wnt/ß-catenin signaling pathway. Following treatment with NGR1, immunocytochemistry was used to detect expression of Tuj1 and MAP2, and RT-qPCR was used to measure mRNA levels of key factors in the Wnt signaling pathway. RESULTS: Results showed that NGR1 promotes growth of cultured neurons and significantly upregulates mRNA levels of ß-catenin, Dishevelled, and Frizzled. To further confirm whether NGR1 promoted cortical neuron growth via the Wnt/ß-catenin signaling pathway, we knocked down ß- catenin mRNA by siRNA interference; following NGR1 treatment of ß-catenin-knockdown neurons, ß-catenin mRNA levels increased significantly. CONCLUSION: In conclusion, these results demonstrate that NGR1 promotes growth of cultured cortical neurons from the neonatal rat, possibly via the Wnt/ß-catenin signaling pathway.

[Expression of saponin biosynthesis related genes in different tissues of Panax quinquefolius].

The relationship between saponin content of Panax quinquefolius in different parts of the organization and expression of ginsenoside biosynthesis related gene was obtained by the correlation analysis between saponin content and gene expression. The 14 tissue parts of P. quinquefolius were studied, six saponins in P. quinquefolius. Samples (ginsenoside Rg1, Re, Rb1, Rc, Rb2 and Rd), group saponins and total saponins were determined by high performance liquid chromatography and vanillin-sulfuric acid colorimetric method. Simultaneously, the expression levels of 7 ginsenoside biosynthesis related genes (SQS, OSC, DS, ß-AS, SQE, P450 and FPS) in different tissues of P. quinquefolius were determined by Real-time fluorescence quantitative PCR. Although 7 kinds of ginsenoside biosynthesis related enzyme gene in the P. quinquefolius involved in ginsenoside synthesis, the expression of ß-AS and P450 genes had no significant effect on the content of monosodium saponins, grouping saponins and total saponins, FPS, SQS, OSC, DS and SQE had significant or extremely significant on the contents of single saponins Re, Rg1, Rb1, Rd, group saponin PPD and PPT, total saponin TMS and total saponin TS (P<0.05 or P<0.01). The biosynthesis of partial saponins, grouping saponins and total saponins in P. quinquefolius was affected by the interaction of multiple enzyme genes in the saponin synthesis pathway, the content of saponins in different tissues of P. quinquefolius was determined by the differences in the expression of key enzymes in the biosynthetic pathway. Therefore, this study further clarified that FPS, SQS, OSC, DS and SQE was the key enzyme to control the synthesis of saponins in P. quinquefolius by correlation analysis, the biosynthesis of ginsenosides in P. quinquefolius was regulated by these five kind of enzymes in cluster co-expression of interaction mode.

Enhanced expression of ginsenoside biosynthetic genes and in vitro ginsenoside production in elicited Panax sikkimensis (Ban) cell suspensions.

Dual metabolite, i.e., ginsenoside and anthocyanin, co-accumulating cell suspensions of Panax sikkimensis were subjected to elicitation with culture filtrates of Serratia marcescens (SD 21), Bacillus subtilis (FL11), Trichoderma atroviridae (TA), and T. harzianum (TH) at 1.25% and 2.5% v/v for 1- and 3-week duration. The fungal-derived elicitors (TA and TH) did not significantly affect biomass accumulation; however, bacterial elicitors (SD 21 and FL11), especially SD 21, led to comparable loss in biomass growth. In terms of ginsenoside content, differential responses were observed. A maximum of 3.2-fold increase (222.2 mg/L) in total ginsenoside content was observed with the use of 2.5% v/v TH culture filtrate for 1 week. Similar ginsenoside accumulation was observed with the use of 1-week treatment with 2.5% v/v SD 21 culture filtrate (189.3 mg/L) with a 10-fold increase in intracellular Rg2 biosynthesis (31 mg/L). Real-time PCR analysis of key ginsenoside biosynthesis genes, i.e., FPS, SQS, DDS, PPDS, and PPTS, revealed prominent upregulation of particularly PPTS expression (20-23-fold), accounting for the observed enhancement in protopanaxatriol ginsenosides. However, none of the elicitors led to successful enhancement in in vitro anthocyanin accumulation as compared to control values.

Panax ginseng genome examination for ginsenoside biosynthesis.

Ginseng, which contains ginsenosides as bioactive compounds, has been regarded as an important traditional medicine for several millennia. However, the genetic background of ginseng remains poorly understood, partly because of the plant's large and complex genome composition. We report the entire genome sequence of Panax ginseng using next-generation sequencing. The 3.5-Gb nucleotide sequence contains more than 60% repeats and encodes 42 006 predicted genes. Twenty-two transcriptome datasets and mass spectrometry images of ginseng roots were adopted to precisely quantify the functional genes. Thirty-one genes were identified to be involved in the mevalonic acid pathway. Eight of these genes were annotated as 3-hydroxy-3-methylglutaryl-CoA reductases, which displayed diverse structures and expression characteristics. A total of 225 UDP-glycosyltransferases (UGTs) were identified, and these UGTs accounted for one of the largest gene families of ginseng. Tandem repeats contributed to the duplication and divergence of UGTs. Molecular modeling of UGTs in the 71st, 74th, and 94th families revealed a regiospecific conserved motif located at the N-terminus. Molecular docking predicted that this motif captures ginsenoside precursors. The ginseng genome represents a valuable resource for understanding and improving the breeding, cultivation, and synthesis biology of this key herb.

Analysis of the Panax ginseng stem/leaf transcriptome and gene expression during the leaf expansion period.

Ginseng (Panax ginseng C.A Meyer) is a widely used herbal remedy, however, the majority of studies have focused on the roots, with less known about the aerial regions of the plant. As the stems and leaves are the primary aerial tissues, the present study characterized their transcriptional profiles using Illumina next­generation sequencing technology. The gene expression profiles and the functional genes of ginseng stems (GS) and leaves (GL) were analyzed during the leaf­expansion period. cDNA libraries of the GS and GL of 5­year­old ginseng plants were separately constructed. In the GS library, 38,000,000 sequencing reads were produced. These reads were assembled into 99,809 unique sequences with a mean size of 572 bp, and 57,371 sequences were identified based on similarity searches against known proteins. The assembled sequences were annotated using Gene Ontology terms, Clusters of Orthologous Groups classifications and Kyoto Encyclopedia of Genes and Genomes pathways. For GL, >118,000,000 sequencing reads were produced, which were assembled into 73,163 unique sequences, from which 50,523 sequences were identified. Additionally, several genes involved in the regulation of growth­related, stress­related, pathogenesis­related, and chlorophyll metabolism­associated proteins were found and expressed at high levels, with low expression levels of ginsenoside biosynthesis enzymes also found. The results of the present study provide a valuable useful sequence resource for ginseng in general, and specifically for further investigations of the functional genomics and molecular genetics of GS and GL during early growth.

Production of a bioactive unnatural ginsenoside by metabolically engineered yeasts based on a new UDP-glycosyltransferase from Bacillus subtilis.

Ginsenosides are the main bioactive constituents of Panax species, which are biosynthesized by glycosylation at C3-OH and/or C20-OH of protopanaxadiol (PPD), C6-OH and/or C20-OH of protopanaxatriol (PPT). The C12-glycosylated ginsenosides have scarcely been identified from Panax species. The C12-glycosylated ginsenosides produced from PPD by chemical semi-synthesis have been reported to exhibit higher cytotoxicity than the natural ginsenosides. However, the chemical semi-synthesis approach is not practical due to its complexity and high cost. In our study, a new UDP-glycosyltransferase UGT109A1 was identified from Bacillus subtilis. This enzyme transferred a glucose moiety to C3-OH and C20-OH of dammarenediol-II (DM), C3-OH and C12-OH of PPD and PPT respectively to produce the unnatural ginsenosides 3ß-O-Glc-DM, 3ß,20S-Di-O-Glc-DM, 3ß,12ß-Di-O-Glc-PPD and 3ß,12ß-Di-O-Glc-PPT. Among these unnatural ginsenosides, 3ß,12ß-Di-O-Glc-PPT is a new compound which has never been reported before. The anti-cancer activities of these unnatural ginsenosides were evaluated in vitro and in vivo. 3ß,12ß-Di-O-Glc-PPD exhibited higher anti-lung cancer activity than Rg3, which is the most active natural ginsenoside against lung cancer. Finally, we constructed metabolically engineered yeasts to produce 3ß,12ß-Di-O-Glc-PPD by introducing the genes encoding B. subtilis UGT109A1, Panax ginseng dammarenediol-II synthase (DS), P. ginseng cytochrome P450-type protopanaxadiol synthase (PPDS) together with Arabidopsis thaliana NADPH-cytochrome P450 reductase (ATR1) into Saccharomyces cerevisiae INVSc1. The yield of 3ß,12ß-Di-O-Glc-PPD was increased from 6.17mg/L to 9.05mg/L by overexpressing tHMG1. Thus, this study has established an alternative route to produce the unnatural ginsenoside 3ß,12ß-Di-O-Glc-PPD by synthetic biology strategies, which provides a promising candidate for anti-cancer drug discovery.

Biosynthesis of plant-derived ginsenoside Rh2 in yeast via repurposing a key promiscuous microbial enzyme.

Ginsenoside Rh2 is a potential anticancer drug isolated from medicinal plant ginseng. Fermentative production of ginsenoside Rh2 in yeast has recently been investigated as an alternative strategy compared to extraction from plants. However, the titer was quite low due to low catalytic capability of the key ginseng glycosyltransferase in microorganisms. Herein, we have demonstrated high-level production of ginsenoside Rh2 in Saccharomyces cerevisiae via repurposing an inherently promiscuous glycosyltransferase, UGT51. The semi-rationally designed UGT51 presented an ~1800-fold enhanced catalytic efficiency (kcat/Km) for converting protopanaxadiol to ginsenoside Rh2 in vitro. Introducing the mutant glycosyltransferase gene into yeast increased Rh2 production from 0.0032 to 0.39mg/g dry cell weight (DCW). Further metabolic engineering, including preventing Rh2 degradation and increasing UDP-glucose precursor supply, increased Rh2 production to 2.90mg/g DCW, which was more than 900-fold higher than the starting strain. Finally, fed-batch fermentation in a 5-L bioreactor led to production of ~300mg/L Rh2, which was the highest titer reported.