Enhanced triterpene accumulation in Panax ginseng hairy roots overexpressing mevalonate-5-pyrophosphate decarboxylase and farnesyl pyrophosphate synthase

Transcription factor PgNAC72 activates DAMMARENEDIOL SYNTHASE expression to promote ginseng saponin biosynthesis

Ginsenosides, the primary bioactive constituents in ginseng (Panax ginseng), possess substantial pharmacological potential and are in high demand in the market. The plant hormone methyl jasmonate (MeJA) effectively elicits ginsenoside biosynthesis in P. ginseng, though the regulatory mechanism remains largely unexplored. NAC transcription factors are critical in intricate plant regulatory networks and participate in numerous plant physiological activities. In this study, we identified a MeJA-responsive NAC transcription factor gene, PgNAC72, from a transcriptome library produced from MeJA-treated P. ginseng callus. Predominantly expressed in P. ginseng flowers, PgNAC72 localizes to the nucleus. Overexpressing PgNAC72 (OE-PgNAC72) in P. ginseng callus notably elevated total saponin levels, particularly dammarane-type ginsenosides, by upregulating dammarenediol synthase (PgDDS), encoding a key enzyme in the ginsenoside biosynthesis pathway. Electrophoretic mobility shift assays and dual-luciferase assays confirmed that PgNAC72 binds to the NAC-binding elements in the PgDDS promoter, thereby activating its transcription. Further RNA-seq and terpenoid metabolomic data in the OE-PgNAC72 line confirmed that PgNAC72 enhances ginsenoside biosynthesis. These findings uncover a regulatory role of PgNAC72 in MeJA-mediated ginsenoside biosynthesis, providing insights into the ginsenoside regulatory network and presenting a valuable target gene for metabolic engineering.

Strategies, Achievements, and Potential Challenges of Plant and Microbial Chassis in the Biosynthesis of Plant Secondary Metabolites

Diverse secondary metabolites in plants, with their rich biological activities, have long been important sources for human medicine, food additives, pesticides, etc. However, the large-scale cultivation of host plants consumes land resources and is susceptible to pest and disease problems. Additionally, the multi-step and demanding nature of chemical synthesis adds to production costs, limiting their widespread application. In vitro cultivation and the metabolic engineering of plants have significantly enhanced the synthesis of secondary metabolites with successful industrial production cases. As synthetic biology advances, more research is focusing on heterologous synthesis using microorganisms. This review provides a comprehensive comparison between these two chassis, evaluating their performance in the synthesis of various types of secondary metabolites from the perspectives of yield and strategies. It also discusses the challenges they face and offers insights into future efforts and directions.

Genome-wide characterization of the bHLH gene family in Gynostemma pentaphyllum reveals its potential role in the regulation of gypenoside biosynthesis

BACKGROUND

Gynostemma pentaphyllum, an ancient Chinese herbal medicine, serves as a natural source of gypenosides with significant medicinal properties. Basic helix-loop-helix (bHLH) transcription factors play pivotal roles in numerous biological processes, especially in the regulation of secondary metabolism in plants. However, the characteristics and functions of the bHLH genes in G. pentaphyllum remain unexplored, and their regulatory role in gypenoside biosynthesis remains poorly elucidated.

RESULTS

This study identified a total of 111 bHLH members in G. pentaphyllum (GpbHLHs), categorizing them into 26 subgroups based on shared conserved motif compositions and gene structures. Collinearity analysis illustrated that segmental duplications predominately lead to the evolution of GpbHLHs, with most duplicated GpbHLH gene pairs undergoing purifying selection. Among the nine gypenoside-related GpbHLH genes, two GpbHLHs (GpbHLH15 and GpbHLH58) were selected for further investigation based on co-expression analysis and functional prediction. The expression of these two selected GpbHLHs was dramatically induced by methyl jasmonate, and their nuclear localization was confirmed. Furthermore, yeast one-hybrid and dual-luciferase assays demonstrated that GpbHLH15 and GpbHLH58 could bind to the promoters of the gypenoside biosynthesis pathway genes, such as GpFPS1, GpSS1, and GpOSC1, and activate their promoter activity to varying degrees.

CONCLUSIONS

In conclusion, our findings provide a detailed analysis of the bHLH family and valuable insights into the potential use of GpbHLHs to enhance the accumulation of gypenosides in G. pentaphyllum.

Transcriptome-Wide Identification and Integrated Analysis of a UGT Gene Involved in Ginsenoside Ro Biosynthesis in Panax ginseng

Panax ginseng as a traditional medicinal plant with a long history of medicinal use. Ginsenoside Ro is the only oleanane-type ginsenoside in ginseng, and has various pharmacological activities, including anti-inflammatory, detoxification, and antithrombotic activities. UDP-dependent glycosyltransferase (UGT) plays a key role in the synthesis of ginsenoside, and the excavation of UGT genes involved in the biosynthesis of ginsenoside Ro has great significance in enriching ginsenoside genetic resources and further revealing the synthesis mechanism of ginsenoside. In this work, ginsenoside-Ro-synthesis-related genes were mined using the P. ginseng reference-free transcriptome database. Fourteen hub transcripts were identified by differential expression analysis and weighted gene co-expression network analysis. Phylogenetic and synteny block analyses of PgUGAT252645, a UGT transcript among the hub transcripts, showed that PgUGAT252645 belonged to the UGT73 subfamily and was relatively conserved in ginseng plants. Functional analysis showed that PgUGAT252645 encodes a glucuronosyltransferase that catalyzes the glucuronide modification of the C3 position of oleanolic acid using uridine diphosphate glucuronide as the substrate. Furthermore, the mutation at 622 bp of its open reading frame resulted in amino acid substitutions that may significantly affect the catalytic activity of the enzyme, and, as a consequence, affect the biosynthesis of ginsenoside Ro. Results of the in vitro enzyme activity assay of the heterologous expression product in E. coli of PgUGAT252645 verified the above analyses. The function of PgUGAT252645 was further verified by the result that its overexpression in ginseng adventitious roots significantly increased the content of ginsenoside Ro. The present work identified a new UGT gene involved in the biosynthesis of ginsenoside Ro, which not only enriches the functional genes in the ginsenoside synthesis pathway, but also provides the technical basis and theoretical basis for the in-depth excavation of ginsenoside-synthesis-related genes.

Carvacrol as a Stimulant of the Expression of Key Genes of the Ginsenoside Biosynthesis Pathway and Its Effect on the Production of Ginseng Saponins in Panax quinquefolium Hairy Root Cultures

The accumulation of ginsenosides (triterpenic saponins) was determined in Panax quinquefolium hairy root cultures subjected to an elicitation process using carvacrol at 5, 10, 25, 50, 100, 250, and 500 μM concentrations during 24 and 72 h exposure. This study was the first one in which carvacrol was applied as an elicitor. The content of eight ginsenosides, Rb1, Rb2, Rb3, Rc, Rd, Rg1, Rg2, and Re, was determined using HPLC analysis. Moreover, the quantitative RT-PCR method was applied to assess the relative expression level of farnesyl diphosphate synthase, squalene synthase, and dammarenediol synthase genes in the studied cultures. The addition of carvacrol (100 μM) was an effective approach to increase the production of ginsenosides. The highest content and productivity of all detected saponins were, respectively, 20.01 mg∙g-1 d.w. and 5.74 mg∙L-1∙day-1 after 72 h elicitation. The production profile of individual metabolites in P. quinquefolium cultures changed under the influence of carvacrol. The biosynthesis of most examined protopanaxadiol derivatives was reduced under carvacrol treatment. In contrast, the levels of ginsenosides belonging to the Rg group increased. The strongest effect of carvacrol was noticed for Re metabolites, achieving a 7.72-fold increase in comparison to the control. Saponin Rg2, not detected in untreated samples, was accumulated after carvacrol stimulation, reaching its maximum concentration after 72 h exposure to 10 μM elicitor.

Lessons learned from metabolic engineering in hairy roots: Transcriptome and metabolic profile changes caused by Rhizobium-mediated plant transformation in Cucurbitaceae species

Cucurbitaceae species are used in traditional medicine around the world. Cucurbitacins are highly oxygenated triterpenoids found in Cucurbitaceae species and exhibit potent anticancer activity alone and in combination with other existing chemotherapeutic drugs. Therefore, increasing production of these specialized metabolites is of great relevance. We recently showed that hairy roots of Cucurbita pepo can be used as a platform for metabolic engineering of cucurbitacins to modify their structure and increase their production. To study the changes in cucurbitacin accumulation upon formation of hairy roots, an empty vector (EV) control and Cucurbitacin inducing bHLH transcription factor 1 (CpCUCbH1)-overexpressing hairy roots of C. pepo were compared to untransformed (WT) roots. Whilst CpCUCbH1-overexpression increased production of cucurbitacins I and B by 5-fold, and cucurbitacin E by 3-fold when compared to EV lines, this increase was not significantly different when compared to WT roots. This indicated that Rhizobium rhizogenes transformation lowered the cucurbitacins levels in hairy roots, but that increasing expression of cucurbitacin biosynthetic genes by CpCUCbH1-overexpression restored cucurbitacin production to WT levels. Subsequent metabolomic and RNA-seq analysis indicated that the metabolic profile and transcriptome of hairy roots was significantly changed when compared to WT roots. Interestingly, it was observed that 11% of the differentially expressed genes were transcription factors. It was noteworthy that the majority of transcripts showing highest Pearson correlation coefficients to the Rhizobium rhizogenes genes rolB, rolC and ORF13a, were predicted to be transcription factors. In summary, hairy roots are an excellent platform for metabolic engineering of plant specialized metabolites, but these extensive transcriptome and metabolic profile changes should be considered in subsequent studies.

Genetic and molecular dissection of ginseng (Panax ginseng Mey.) germplasm using high-density genic SNP markers, secondary metabolites, and gene expressions

Genetic and molecular knowledge of a species is crucial to its gene discovery and enhanced breeding. Here, we report the genetic and molecular dissection of ginseng, an important herb for healthy food and medicine. A mini-core collection consisting of 344 cultivars and landraces was developed for ginseng that represents the genetic variation of ginseng existing in its origin and diversity center. We sequenced the transcriptomes of all 344 cultivars and landraces; identified over 1.5 million genic SNPs, thereby revealing the genic diversity of ginseng; and analyzed them with 26,600 high-quality genic SNPs or a selection of them. Ginseng had a wide molecular diversity and was clustered into three subpopulations. Analysis of 16 ginsenosides, the major bioactive components for healthy food and medicine, showed that ginseng had a wide variation in the contents of all 16 ginsenosides and an extensive correlation of their contents, suggesting that they are synthesized through a single or multiple correlated pathways. Furthermore, we pair-wisely examined the relationships between the cultivars and landraces, revealing their relationships in gene expression, gene variation, and ginsenoside biosynthesis. These results provide new knowledge and new genetic and genic resources for advanced research and breeding of ginseng and related species.

Transcriptome-Wide Integrated Analysis of the PgGT25-04 Gene in Controlling Ginsenoside Biosynthesis in Panax ginseng

Panax ginseng is a valuable medicinal herb of the Araliaceae family with various pharmacological activities. The Trihelix transcription factors family is involved in growth and secondary metabolic processes in plants, but no studies have been reported on the involvement of Trihelix genes in secondary metabolic processes in ginseng. In this study, weighted co-expression network analysis, correlation analysis between PgGTs and ginsenosides and key enzyme genes, and interaction network analysis between PgGTs and key enzyme genes were used to screen out the PgGT25-04 gene, which was negatively correlated with ginsenoside synthesis. Using ABA treatment of ginseng hair roots, PgGT genes were found to respond to ABA signals. Analysis of the sequence characteristics and expression pattern of the PgGT25-04 gene in ginseng revealed that its expression is spatiotemporally specific. The interfering vector pBI121-PgGT25-04 containing the PgGT25-04 gene was constructed, and the ginseng adventitious roots were transformed using the Agrobacterium-mediated method to obtain the pBI121-PgGT25-04 positive hairy root monocot line. The saponin contents of positive ginseng hair roots were measured by HPLC, and the changes in PgGT25-04 and key enzyme genes in positive ginseng hair roots were detected via fluorescence quantitative RT-PCR. These results preliminarily identified the role of the PgGT25-04 gene in the secondary metabolism of ginseng in Jilin to provide a theoretical basis for the study of Trihelix transcription factors in Panax ginseng.

Genes and Regulatory Mechanisms for Ginsenoside Biosynthesis

Panax ginseng is a medicinal plant belonging to the Araliaceae family. Ginseng is known as the king of oriental medicine, which has been practiced since ancient times in East Asian countries and globally in the modern era. Ginseng is used as an adaptogen, and research shows that it has several pharmacological benefits for various ailments such as cancer, inflammation, diabetes, and neurological symptoms. The pharmacological benefits of ginseng are attributed to the triterpenoid saponin ginsenosides found throughout the Panax ginseng species, which are abundant in its root and are found exclusively in P. ginseng and Panax quinquefolius. Recently, with the completion of the entire ginseng genome sequencing and the construction of the ginseng genome database, it has become possible to access information about many genes newly predicted to be involved in ginsenoside biosynthesis. This review briefly summarizes the current progress in ginseng genome analysis and genes involved in ginsenoside biosynthesis, proposing directions for functional studies of the predicted genes related to ginsenoside production and its regulation.

Transcriptomics-metabolomics joint analysis: New highlight into the triterpenoid saponin biosynthesis in quinoa (Chenopodium quinoa Willd.)

Quinoa (Chenopodium quinoa Willd.) contains various physiologically active substances, including vitamins, polyphenols, flavonoids, phytosterols, and saponins. Research showed that saponins were the protective substances in the outer layer of quinoa seeds to defend against microbes, herbivores, and insects. Because the aglycones of quinoa saponins are triterpenoids, they are called triterpenoid saponins (TSs). In addition, the presence of TS imparted bitterness in quinoa and resulted in anticancer and anti-inflammatory effects. In this study, the seeds of low-saponin quinoa, NT376-2 (N), and high-saponin quinoa, B-12071(B), at 30 and 60 days after flowering (DAF) were used to measure the TS content and evaluated for their transcriptomic and metabolomic profiles. The amounts of TS were found to significantly differ between all possible comparisons: N and B at 30 DAF (N1_vs_B1), N and B at 60 DAF (N2_vs_B2), N at 30 DAF and 60 DAF (N1_vs_N2), and B at 30 DAF and 60 DAF (B1_vs_B2). RNA sequencing (RNA-seq) was used to screen differentially expressed genes (DEGs) and revealed 14,703 upregulated DEGs and 26,267 downregulated DEGs in the four comparison groups. The 311 overlapping DEGs found in the four comparisons were used for Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses to screen for DEGs related to TS biosynthesis in quinoa. Metabolomics analysis identified acetyl-CoA, 1-hydroxy-2-methyl-2-butenyl-4-diphosphate, farnesal, and (S)-2,3-epoxysqualene as the key differentially accumulated metabolites (DAMs). Transcriptomics-metabolomics joint analysis showed that triterpenoid biosynthesis and terpenoid backbone biosynthesis were the enriched pathways of TS biosynthesis; farnesal were the key DAMs shared in the four comparison groups and associated with 10 key candidate DEGs related to TS biosynthesis in quinoa. These results provided important references for in-depth research on the metabolic mechanism of TS in quinoa.

Natural products of medicinal plants: biosynthesis and bioengineering in post-genomic era

Globally, medicinal plant natural products (PNPs) are a major source of substances used in traditional and modern medicine. As we human race face the tremendous public health challenge posed by emerging infectious diseases, antibiotic resistance and surging drug prices etc., harnessing the healing power of medicinal plants gifted from mother nature is more urgent than ever in helping us survive future challenge in a sustainable way. PNP research efforts in the pre-genomic era focus on discovering bioactive molecules with pharmaceutical activities, and identifying individual genes responsible for biosynthesis. Critically, systemic biological, multi- and inter-disciplinary approaches integrating and interrogating all accessible data from genomics, metabolomics, structural biology, and chemical informatics are necessary to accelerate the full characterization of biosynthetic and regulatory circuitry for producing PNPs in medicinal plants. In this review, we attempt to provide a brief update on the current research of PNPs in medicinal plants by focusing on how different state-of-the-art biotechnologies facilitate their discovery, the molecular basis of their biosynthesis, as well as synthetic biology. Finally, we humbly provide a foresight of the research trend for understanding the biology of medicinal plants in the coming decades.

Content of sterols in in vitro propagated Chamerion angustifolium (L.) Holub plants

Introduction: Chamerion angustifolium (L.) Holub (syn. Epilobium angustifolium L.) plants have been used in the treatment and alleviating symptoms of mild Benign Prostatic Hyperplasia (BPH). Plants are abundant in polyphenols, particularly ellagitannins, phenolic acids and flavonoids. Apart from polyphenols, herb of this species also contains steroids, triterpenes and fatty acids.

Objective: The aim of this study was to determine the content of campesterol, β-sitosterol and stigmasterol in C. angustifolium genotypes cultivated in vitro.

Methods: Plants grown in vitro and the plants harvested from field were subjected to the HPLC-DAD analysis.

Results: The investigated genotypes differed in sterol content. Stigmasterol (375.64–577.77 mg/100 g of dry weight – DW) was a predominant compound among the tested sterols. In contrast to in vitro cultures, plants harvested from field synthesized mainly β-sitosterol (103.05 mg/100 g DW), whereas campesterol and stigmasterol were less abundant.

Conclusions: C. angustifolium in vitro cultures are rich source of phytosterols, particularly stigmasterol. Genotype had a significant effect on phytosterol accumulation under in vitro conditions.

Binding proteins PnCOX11 and PnDCD strongly respond to GA and ABA in Panax notoginseng

Panax notoginseng saponins (PNS) are one of the main active ingredients of Panax notoginseng, a representative plant of the genus Panax. However, the detailed regulation mechanism of PNS biosynthesis remains elusive. Therefore, a sequence of upstream promoters of PnSS and PnSE were cloned and analyzed firstly. GUS quantitative results showed that the upstream promoters could specifically and significantly respond to exogenous GA and ABA signals. To further identify the binding proteins that respond to peripheral hormones, PnCOX11 and PnDCD were screened and identified from the P. notoginseng cDNA library. The Y1H experiment verified the interaction between the above two binding proteins and the promoters. Several online software was used to analyze the domains, secondary structures, three-dimensional structures, and phylogenetic trees of the two binding proteins. Subcellular localization analysis exhibited that PnCOX11 was mainly located in the chloroplast, while PnDCD was located in the cytoplasm and nucleus. Prokaryotic expression demonstrated that the recombinant proteins had a high concentration under the induction of IPTG. This study can provide a fundamental date for the subsequent thorough investigation of the transcription regulatory mechanism of PNS biosynthesis.

Metabolic Modifications in Terpenoid and Steroid Pathways Triggered by Methyl Jasmonate in Taxus × media Hairy Roots

The in vitro cultures of Taxus spp. were one of the first plant in vitro systems proved to exert the positive effect of elicitation with methyl jasmonate (MeJA) on the biosynthesis of specialized metabolites. The main aim of the present study is to examine the effect of MeJA treatment on the steroid and triterpenoid content of two genetically different hairy root lines of Taxus × media, KT and ATMA. The results revealed that the two lines differed in the total content of steroids and triterpenoids (in the ATMA root line, their amounts were lower than those in the KT line by 43% and 30%, respectively), but not in the composition of these compounds. The metabolic response to elicitation with MeJA was different: in the KT root line, the content of steroids decreased by 18%, whereas it increased by 38% in the ATMA line. Several metabolic features were common, including the characteristic changes in the ratio of sitosterol to stigmasterol content, caused by the very sharp boost in stigmasterol levels, the increase in the amount of glycoside forms of sterols, as well as in triterpenoid and total phenolic content. It is the first report on modifications of the terpenoid biosynthetic pathway in Taxus hairy root cultures triggered by MeJA, concerning steroids and triterpenoids.

Genome-Wide Identification of R2R3-MYB Transcription Factors: Discovery of a "Dual-Function" Regulator of Gypenoside and Flavonol Biosynthesis in Gynostemma pentaphyllum

The R2R3-MYB gene family participates in several plant physiological processes, especially the regulation of the biosynthesis of secondary metabolites. However, little is known about the functions of R2R3-MYB genes in Gynostemma pentaphyllum (G. pentaphyllum), a traditional Chinese medicinal herb that is an excellent source of gypenosides (a class of triterpenoid saponins) and flavonoids. In this study, a systematic genome-wide analysis of the R2R3-MYB gene family was performed using the recently sequenced G. pentaphyllum genome. In total, 87 R2R3-GpMYB genes were identified and subsequently divided into 32 subgroups based on phylogenetic analysis. The analysis was based on conserved exon-intron structures and motif compositions within the same subgroup. Collinearity analysis demonstrated that segmental duplication events were majorly responsible for the expansion of the R2R3-GpMYB gene family, and Ka/Ks analysis indicated that the majority of the duplicated R2R3-GpMYB genes underwent purifying selection. A combination of transcriptome analysis and quantitative reverse transcriptase-PCR (qRT-PCR) confirmed that Gynostemma pentaphyllum myeloblastosis 81 (GpMYB81) along with genes encoding gypenoside and flavonol biosynthetic enzymes exhibited similar expression patterns in different tissues and responses to methyl jasmonate (MeJA). Moreover, GpMYB81 could bind to the promoters of Gynostemma pentaphyllum farnesyl pyrophosphate synthase 1 (GpFPS1) and Gynostemma pentaphyllum chalcone synthase (GpCHS), the key structural genes of gypenoside and flavonol biosynthesis, respectively, and activate their expression. Altogether, this study highlights a novel transcriptional regulatory mechanism that suggests that GpMYB81 acts as a "dual-function" regulator of gypenoside and flavonol biosynthesis in G. pentaphyllum.

Activity and function studies of the promoter cis-acting elements of the key enzymes in saponins biosynthesis of DS from Panax notoginseng

Panax notoginseng is a traditional Chinese medicine for the treatment of blood diseases, in which saponins were the main active components. Dammarenediol synthase (DS) is a key enzyme in the saponin synthesis pathway of P. notoginseng. The promoter is an important region to regulate gene expression, and the study of the promoter sequence provides important evidence for revealing the mechanism of gene expression regulation. However, there was still little research on the promoter function of P. notoginseng. In this study, the 1382 bp promoter upstream of DS from P. notoginseng was cloned and sequenced. The promoter sequence was analyzed by online databases. The plant expression vector fused with the β-glucuronidase gene was constructed and transferred into Agrobacterium tumefaciens. Then tobacco was injected, and its response to exogenous hormones (gibberellin and abscisic acid) was studied by transient expression to verify its unique action elements. The results showed that the tobacco leaves transferred with DS promoter had significantly increased GUS protease activity after spraying GA and ABA, indicating that both DS promoter can specifically and significantly respond to exogenous GA and ABA signal. These findings will help us to better understand the regulatory mechanisms of the upstream region of the DS gene and provide a basis for future research on the interaction of cis-acting elements of promoters with related transcription factors.

In silico/computational analysis of mevalonate pyrophosphate decarboxylase gene families in Campanulids

Mevalonate pyrophosphate decarboxylase (MPD) is a key enzyme in terpenoid biosynthesis. MPD plays an important role in the upstream regulation of secondary plant metabolism. However, studies on the MPD gene are relatively very few despite its importance in plant metabolism. Currently, no systematic analysis has been conducted on the MPD gene in plants under the order Apiales, which comprises important medicinal plants such as Panax ginseng and Panax notoginseng. This study sought to explore the structural characteristics of the MPD gene and the effect of adaptive evolution on the gene by comparing and analyzing MPD gene sequences of different campanulids species. For that, phylogenetic and adaptive evolution analyses were carried out using sequences for 11 Campanulids species. MPD sequence characteristics of each species were then analyzed, and the collinearity analysis of the genes was performed. As a result, a total of 21 MPD proteins were identified in 11 Campanulids species through BLAST analysis. Phylogenetic analysis, physical and chemical properties prediction, gene family analysis, and gene structure prediction showed that the MPD gene has undergone purifying selection and exhibited highly conserved structure. Analysis of physicochemical properties further showed that the MPD protein was a hydrophilic protein without a transmembrane region. Moreover, collinearity analysis in Apiales showed that MPD gene on chromosome 2 of D. carota and chromosome 1 of C. sativum were collinear. The findings showed that MPD gene is highly conserved. This may be a common characteristic of all essential enzymes in the biosynthesis pathways of medicinal plants. Notably, MPD gene is significantly affected by environmental factors which subsequently modulate its expression. The current study’s findings provide a basis for follow-up studies on MPD gene and key enzymes in other medicinal plants.

Enhancement of Phytosterol and Triterpenoid Production in Plant Hairy Root Cultures-Simultaneous Stimulation or Competition?

Plant in vitro cultures, including hairy roots, can be applied for controlled production of valuable natural products, such as triterpenoids and sterols. These compounds originate from the common precursor squalene. Sterols and triterpenoids distinctly differ in their functions, and the 2,3-oxidosqualene cyclization step is often regarded as a branch point between primary and secondary (more aptly: general and specialized) metabolism. Considering the crucial role of phytosterols as membrane constituents, it has been postulated that unconstrained biosynthesis of triterpenoids can occur when sterol formation is already satisfied, and these compounds are no longer needed for cell growth and division. This hypothesis seems to follow directly the growth-defense trade-off plant dilemma. In this review, we present some examples illustrating the specific interplay between the two divergent pathways for sterol and triterpenoid biosynthesis appearing in root cultures. These studies were significant for revealing the steps of the biosynthetic pathway, understanding the role of particular enzymes, and discovering the possibility of gene regulation. Currently, hairy roots of many plant species can be considered not only as an efficient tool for production of phytochemicals, but also as suitable experimental models for investigations on regulatory mechanisms of plant metabolism.

Chromosome-level genome assembly of Gynostemma pentaphyllum provides insights into gypenoside biosynthesis

Gynostemma pentaphyllum (Thunb.) Makino is an economically valuable medicinal plant belonging to the Cucurbitaceae family that produces the bioactive compound gypenoside. Despite several transcriptomes having been generated for G. pentaphyllum, a reference genome is still unavailable, which has limited the understanding of the gypenoside biosynthesis and regulatory mechanism. Here, we report a high-quality G. pentaphyllum genome with a total length of 582 Mb comprising 1,232 contigs and a scaffold N50 of 50.78 Mb. The G. pentaphyllum genome comprised 59.14% repetitive sequences and 25,285 protein-coding genes. Comparative genome analysis revealed that G. pentaphyllum was related to Siraitia grosvenorii, with an estimated divergence time dating to the Paleogene (∼48 million years ago). By combining transcriptome data from seven tissues, we reconstructed the gypenoside biosynthetic pathway and potential regulatory network using tissue-specific gene co-expression network analysis. Four UDP-glucuronosyltransferases (UGTs), belonging to the UGT85 subfamily and forming a gene cluster, were involved in catalyzing glycosylation in leaf-specific gypenoside biosynthesis. Furthermore, candidate biosynthetic genes and transcription factors involved in the gypenoside regulatory network were identified. The genetic information obtained in this study provides insights into gypenoside biosynthesis and lays the foundation for further exploration of the gypenoside regulatory mechanism.

Ginsenosides in Panax genus and their biosynthesis

Ginsenosides are a series of glycosylated triterpenoids which belong to protopanaxadiol (PPD)-, protopanaxatriol (PPT)-, ocotillol (OCT)- and oleanane (OA)-type saponins known as active compounds of Panax genus. They are accumulated in plant roots, stems, leaves, and flowers. The content and composition of ginsenosides are varied in different ginseng species, and in different parts of a certain plant. In this review, we summarized the representative saponins structures, their distributions and the contents in nearly 20 Panax species, and updated the biosynthetic pathways of ginsenosides focusing on enzymes responsible for structural diversified ginsenoside biosynthesis. We also emphasized the transcription factors in ginsenoside biosynthesis and non-coding RNAs in the growth of Panax genus plants, and highlighted the current three major biotechnological applications for ginsenosides production. This review covered advances in the past four decades, providing more clues for chemical discrimination and assessment on certain ginseng plants, new perspectives for rational evaluation and utilization of ginseng resource, and potential strategies for production of specific ginsenosides.

The dehiscence process in Panax ginseng seeds and the stigmasterol biosynthesis pathway in terms of metabolomics

Background

Ginseng, officially known as Panax ginseng Meyer, has been traditionally used as a medicinal herb, particularly in Asia. Ginseng is propagated from seeds; however, seed germination is challenging, especially in its natural environment on farms. The seeds typically exhibit morphophysiological dormancy and require release from both morphological and physiological dormancy before germination. Although some studies have proposed methods for increasing seed germination rates, the underlying mechanisms of its dormancy release process remain unclear. Here, we investigated metabolic alterations during dehiscence in P. ginseng to determine their potential roles in dormancy release.

Methods

We compared the ginseng seed metabolome before and after dehiscence and the ginsenoside and phytosterol compositions of the seeds in both periods in the presence of related enzymes.

Results

After seed dehiscence, the sugar, amino acid, and squalene concentrations were significantly altered, phytosterols associated with the stigmasterol biosynthesis pathway were increased, while ginsenoside and brassinosteroid levels were not significantly altered. In addition, squalene epoxidase, cycloartenol synthase, 24-methylenesterol C-methyltransferase, and the stigmasterol biosynthesis pathway were activated.

Conclusion

Overall, our findings suggest that morphological activities that facilitate ginseng seed growth are the primary phenomena occurring during the dehiscence process. This study improves the understanding of P. ginseng germination processes and promotes further research of its germination and cultivation.

Structure and Location Studies on Key Enzymes in Saponins Biosynthesis of Panax notoginseng

Panax notoginseng is one of the most widely used traditional herbs for the treatment of various diseases, in which saponins were the main active components. At present, the research of P. notoginseng mainly focused on the discovery of new compounds and pharmacology. However, there were few studies on the molecular mechanism of the synthesis of secondary metabolites of P. notoginseng. In our study, four coding sequences (CDS) encoding the key enzymes involved in saponin biosynthesis were cloned, namely farnesyl diphosphate synthase (FPS), squalene synthase (SS), squalene epoxidase (SE), and dammarenediol-II synthase (DS), which contained open reading frame (ORF) of 1029 bp, 1248 bp, 1614 bp, and 2310 bp, and coded 342, 415, 537, and 769 amino acids, respectively. At the same time, their domains, secondary structures, three-dimensional structures, and phylogenetics trees were analyzed by kinds of bioinformatics tools. Their phylogenetics relationships were also analyzed. In addition, GFP (Green fluorescent protein) fusion genes were constructed by the plasmid transformation system to determine the subcellular localization. The results of subcellular localization showed that FPS, SE, and DS were mainly located in cytomembrane and its surrounding, while SS was located both in cytoplasm and cytomembrane. Our findings provided data demonstrating the expression patterns of genes involved in saponin biosynthesis and would facilitate efforts to further elucidate the biosynthesis of the bioactive components in P. notoginseng.

Identification of key genes involved in the biosynthesis of triterpenic acids in the mint family

Triterpenic acids (TAs), a large group of natural compounds with diverse biological activity, are produced by several plant taxa. Betulinic, oleanolic, and ursolic acids are the most medicinally important TAs and are mainly found in plants of the mint family. Metabolic engineering is strongly dependent on identifying the key genes in biosynthetic pathways toward the products of interest. In this study, gene expression tracking was performed by transcriptome mining, co-expression network analysis, and tissue-specific metabolite-expression analysis in order to identify possible key genes involved in TAs biosynthetic pathways. To this end, taxa-specific degenerate primers of six important genes were designed using an effective method based on the MEME algorithm in a phylogenetically related group of sequences and successfully applied in three members of the Lamiaceae (Rosmarinus officinalis, Salvia officinalis, and Thymus persicus). Based on the results of in-depth data analysis, genes encoding squalene epoxidase and oxido squalene cyclases are proposed as targets for boosting triterpene production. The results emphasize the importance of identifying key genes in triterpene biosynthesis, which may facilitate genetic manipulation or overexpression of target genes.

Metabolomic understanding of intrinsic physiology in Panax ginseng during whole growing seasons

BACKGROUND

Panax ginseng Meyer has widely been used as a traditional herbal medicine because of its diverse health benefits. Amounts of ginseng compounds, mainly ginsenosides, vary according to seasons, varieties, geographical regions, and age of ginseng plants. However, no study has comprehensively determined perturbations of various metabolites in ginseng plants including roots and leaves as they grow.

METHODS

Nuclear magnetic resonance (1H NMR)-based metabolomics was applied to better understand the metabolic physiology of ginseng plants and their association with climate through global profiling of ginseng metabolites in roots and leaves during whole growing periods.

RESULTS

The results revealed that all metabolites including carbohydrates, amino acids, organic acids, and ginsenosides in ginseng roots and leaves were clearly dependent on growing seasons from March to October. In particular, ginsenosides, arginine, sterols, fatty acids, and uracil diphosphate glucose-sugars were markedly synthesized from March until May, together with accelerated sucrose catabolism, possibly associated with climatic changes such as sun exposure time and rainfall.

CONCLUSION

This study highlights the intrinsic metabolic characteristics of ginseng plants and their associations with climate changes during their growth. It provides important information not only for better understanding of the metabolic phenotype of ginseng but also for quality improvement of ginseng through modification of cultivation.

Biogenic Synthesis and Spatial Distribution of Endogenous Phytohormones and Ginsenosides Provide Insights on Their Intrinsic Relevance in Panax ginseng

Ginseng, the root and rhizome of Panax ginseng C. A. Mey., is a well-known and valuable traditional Chinese medicine. The pharmacological activities of ginseng are mainly attributed to the presence of ginsenosides, which are considered to be critical biomarkers for evaluating ginseng quality. The biosynthesis of triterpenes, which serve defensive functions in plants, is regulated by endogenous phytohormones that play key roles in growth and defense of plant populations. However, the role of major hormones that are closely related to secondary metabolism pathways in P. ginseng is poorly understood. To gain insight into their potential correlation, we performed a spatial synthesis analysis and studied the distribution of endogenous phytohormones and ginsenosides in different tissue regions of the entire P. ginseng plant. Gibberellins are growth hormones that accumulate in the fiber root. In contrast, abscisic acid (ABA), salicylic acid (SA), and jasmonic acid (JA), which are considered stress hormones, were predominantly found in the leaf and leaf peduncle. We observed a tissue-specific distribution of phytohormones consistent with the expression of genes involved in hormone biosynthesis that influenced ginsenoside synthesis and distribution. The aim of this study was to investigate the role of different endogenous phytohormones on triterpene metabolites in ginseng innate immunity.

The Effects of Environmental Factors on Ginsenoside Biosynthetic Enzyme Gene Expression and Saponin Abundance

Panax ginseng C.A. Meyer is one of the most important medicinal plants in Northeast China, and ginsenosides are the main active ingredients found in medicinal ginseng. The biosynthesis of ginsenosides is regulated by environmental factors and the expression of key enzyme genes. Therefore, in this experiment, ginseng in the leaf opened stage, the green fruit stage, the red fruit stage, and the root growth stage was used as the test material, and nine individual ginsenosides and total saponins (the sum of the individual saponins) were detected by HPLC (High Performance Liquid Chromatography). There was a trend of synergistic increase and decrease, and saponin accumulation and transfer in different tissues. The expression of key enzyme genes in nine synthetic pathways was detected by real-time PCR, and the correlation between saponin content, gene expression, and ecological factors was analyzed. Correlation analysis showed that in root tissue, PAR (Photosynthetically Active Radiation) and soil water potential had a greater impact on ginsenoside accumulation, while in leaf tissue, temperature and relative humidity had a greater impact on ginsenoside accumulation. The results provide a theoretical basis for elucidating the relationship between ecological factors and genetic factors and their impact on the quality of medicinal materials. The results also have guiding significance for realizing the quality of medicinal materials.

Molecular characterization of anthocyanin and betulinic acid biosynthesis in red and white mulberry fruits using high-throughput sequencing

To better understand the molecular mechanism of color formation in different varieties of the mulberry fruit, we investigated the functional genes related to anthocyanin and betulinic acid biosynthesis using high-throughput transcriptome sequencing and detected the primary and secondary metabolites in the white (Morus alba L. cv. 'Turkey') and red (Morus alba L. cv. 'Cheongil') mulberry cultivars. We obtained 171,702,058 high-quality reads with an average read length of 125 bp. These reads were assembled into 51,272 and 51,159 unigenes in Turkey and Cheongil, respectively. We also identified the genes related to anthocyanin and triterpene biosynthesis and investigated their expression and metabolite profiles. Overall, our transcriptome sequencing provides valuable information that could be used in gene discovery, marker-assisted selection, and investigation of metabolic pathways in mulberry. Additionally, gene expression and metabolite profiles provide new insights into the underlying mechanism of anthocyanin and betulinic acid biosynthesis and relationship between primary and secondary metabolites.

Co-expression of squalene epoxidases with triterpene cyclases boosts production of triterpenoids in plants and yeast

Triterpene cyclases catalyze the first committed step in triterpene biosynthesis, by forming mono- to pentacyclic backbone structures from oxygenated C30 isoprenoid precursors. Squalene epoxidase precedes this cyclization by providing the oxygenated and activated substrate for triterpene biosynthesis. Three squalene epoxidases from Cucurbita pepo (CpSEs) were isolated and shown to have evolved under purifying selection with signs of sites under positive selection in their N- and C-termini. They all localize to the Endoplasmic Reticulum (ER) and produce 2,3-oxidosqualene and 2,3:22,23-dioxidosqualene when expressed in a yeast erg1 (squalene epoxidase) erg7 (lanosterol synthase) double mutant. Co-expression of the CpSEs with four different triterpene cyclases, either transiently in Nicotiana benthamiana or constitutively in yeast, showed that CpSEs boost triterpene production. CpSE2 was the best performing in this regard, which could reflect either increased substrate production or superior channeling of the substrate to the triterpene cyclases. Fluorescence Lifetime Imaging Microscopy (FLIM) analysis with C. pepo cucurbitadienol synthase (CpCPQ) revealed a specific interaction with CpSE2 but not with the other CpSEs. When CpSE2 was transformed into C. pepo hairy root lines, cucurbitacin E production was increased two folds compared to empty vector control lines. This study provides new insight into the importance of SEs in triterpene biosynthesis, suggesting that they may facilitate substrate channeling, and demonstrates that SE overexpression is a new tool for increasing triterpene production in plants and yeast.

Integrated metabolomic and transcriptomic analyses revealed the distribution of saponins in Panax notoginseng

Panax notoginseng is famous for its important therapeutic effects. Saponins are bioactive compounds found in different parts and developmental stages of P. notoginseng plants. Thus, it is urgently to study saponins distribution in different parts and growth ages of P. notoginseng plants. In this study, potential biomarkers were found, and their chemical characteristic differences were revealed through metabolomic analysis. High-performance liquid chromatography data indicated the higher content of saponins (i.e., Rg1, Re, Rd, and Rb1) in the underground parts than that in the aerial parts. 20(S)-Protopanaxadiol saponins were mainly distributed in the aerial parts. Additionally, the total saponin content in the 3-year-old P. notoginseng plant (188.0 mg/g) was 1.4-fold higher than that in 2-year-old plant (130.5 mg/g). The transcriptomic analysis indicated the tissue-specific transcription expression of genes, namely, PnFPS, PnSS, PnSE1, PnSE2, and PnDS, which encoded critical synthases in saponin biosyntheses. These genes showed similar expression patterns among the parts of P. notoginseng plants. The expression levels of these genes in the flowers and leaves were 5.2fold higher than that in the roots and fibrils. These results suggested that saponins might be actively synthesized in the aerial parts and transformed to the underground parts. This study provides insights into the chemical and genetic characteristics of P. notoginseng to facilitate the synthesis of its secondary metabolites and a scientific basis for appropriate collection and rational use of this plant.

Progress on the Studies of the Key Enzymes of Ginsenoside Biosynthesis

As the main bioactive constituents of Panax species, ginsenosides possess a wide range of notable medicinal effects such as anti-cancer, anti-oxidative, antiaging, anti-inflammatory, anti-apoptotic and neuroprotective activities. However, the increasing medical demand for ginsenosides cannot be met due to the limited resource of Panax species and the low contents of ginsenosides. In recent years, biotechnological approaches have been utilized to increase the production of ginsenosides by regulating the key enzymes of ginsenoside biosynthesis, while synthetic biology strategies have been adopted to produce ginsenosides by introducing these genes into yeast. This review summarizes the latest research progress on cloning and functional characterization of key genes dedicated to the production of ginsenosides, which not only lays the foundation for their application in plant engineering, but also provides the building blocks for the production of ginsenosides by synthetic biology.

Study of artemisinin and sugar accumulation in Artemisia vulgaris and Artemisia dracunculus "hairy" root cultures

We studied the effect of genetic transformation on biologically active compound (artemisinin and its co-products (ART) as well as sugars) accumulation in Artemisia vulgaris and Artemisia dracunculus "hairy" root cultures. Glucose, fructose, sucrose, and mannitol were accumulated in A. vulgaris and A. dracunculus "hairy" root lines. Genetic transformation has led in some cases to the sugar content increasing or appearing of nonrelevant for the control plant carbohydrates. Sucrose content was 1.6 times higher in A. vulgaris "hairy" root lines. Fructose content was found to be 3.4 times higher in A. dracunculus "hairy" root cultures than in the control roots. The accumulation of mannitol was a special feature of the leaves of A. vulgaris and A. dracunculus control roots. A. vulgaris "hairy" root lines differed also in ART accumulation level. The increase of ART content up to 1.02 mg/g DW in comparison with the nontransformed roots (up to 0.687 mg/g DW) was observed. Thus, Agrobacterium rhizogenes-mediated genetic transformation can be used for obtaining of A. vulgaris and A. dracunculus "hairy" root culture produced ART and sugars in a higher amount than mother plants.

A literature update elucidating production of Panax ginsenosides with a special focus on strategies enriching the anti-neoplastic minor ginsenosides in ginseng preparations

Ginseng, an oriental gift to the world of healthcare and preventive medicine, is among the top ten medicinal herbs globally. The constitutive triterpene saponins, ginsenosides, or panaxosides are attributed to ginseng's miraculous efficacy towards anti-aging, rejuvenating, and immune-potentiating benefits. The major ginsenosides such as Rb1, Rb2, Rc, Rd., Re, and Rg1, formed after extensive glycosylations of the aglycone "dammaranediol," dominate the chemical profile of this genus in vivo and in vitro. Elicitations have successfully led to appreciable enhancements in the production of these major ginsenosides. However, current research on ginseng biotechnology has been focusing on the enrichment or production of the minor ginsenosides (the less glycosylated precursors of the major ginsenosides) in ginseng preparations, which are either absent or are produced in very low amounts in nature or via cell cultures. The minor ginsenosides under current scientific scrutiny include diol ginsenosides such as Rg3, Rh2, compound K, and triol ginsenosides Rg2 and Rh1, which are being touted as the next "anti-neoplastic pharmacophores," with better bioavailability and potency as compared to the major ginsenosides. This review aims at describing the strategies for ginsenoside production with special attention towards production of the minor ginsenosides from the major ginsenosides via microbial biotransformation, elicitations, and from heterologous expression systems.

Strengthening Triterpene Saponins Biosynthesis by Over-Expression of Farnesyl Pyrophosphate Synthase Gene and RNA Interference of Cycloartenol Synthase Gene in Panax notoginseng Cells

To conform to the multiple regulations of triterpene biosynthesis, the gene encoding farnesyl pyrophosphate synthase (FPS) was transformed into Panax notoginseng (P. notoginseng) cells in which RNA interference (RNAi) of the cycloartenol synthase (CAS) gene had been accomplished. Transgenic cell lines showed both higher expression levels of FPS and lower expression levels of CAS compared to the wild-type (WT) cells. In the triterpene and phytosterol analysis, transgenic cell lines provided a higher accumulation of total triterpene saponins, and a lower amount of phytosterols in comparison with the WT cells. Compared with the cells in which RNAi of the CAS gene was achieved, the cells with simultaneously over-expressed FPS and silenced CAS showed higher triterpene contents. These results demonstrate that over-expression of FPS can break the rate-limiting reaction catalyzed by FPS in the triterpene saponins biosynthetic pathway; and inhibition of CAS expression can decrease the synthesis metabolic flux of the phytosterol branch. Thus, more precursors flow in the direction of triterpene synthesis, and ultimately promote the accumulation of P. notoginseng saponins. Meanwhile, silencing and over-expressing key enzyme genes simultaneously is more effective than just manipulating one gene in the regulation of saponin biosynthesis.

Comparison of Different Strains of Agrobacterium rhizogenes for Hairy Root Induction and Betulin and Betulinic Acid Production in Morus alba

Three Agrobacterium rhizogenes strains were tested for their ability to transform the plant Morus alba L. and to induce production of the secondary metabolites betulin and betulinic acid. All the tested strains of A. rhizogenes (R1601, LBA9402 and R1000) were able to induce hairy root formation in leaf tissue explants. Strain LBA9402 had the highest rate of infection (92.7% ± 8.8%), whereas strain R1601 had the lowest rate (87.4% ± 9.3%). The highest number of hairy roots per explant (5.6 ± 0.5) and the greatest root length (2.4 ± 0.2 mm) were obtained with strain LBA9402. We also evaluated dry weight (a measure of growth) and betulin and betulinic acid production in hairy roots and found that the highest growth (167.8 ± 14.5 mg/flask) occurred after infection with strain LBA9402. Furthermore the highest production of betulin (5.4 ± 0.4 mg/g dry weight) and betulinic acid (2.3 ± 0.2 mg/g dry weight) was noted using strain LBA9402. Among three elicitors, yeast extract showed the highest induction of betulin production (8.7 ± 0.4 mg/g) and silver nitrate induced the highest yield of betulinic acid (4.1 ± 0.2 mg/g). Our study showed that A. rhizogenes strain LBA9402 was the most effective of the three tested strains for production of transformed root cultures and betulin and betulinic acid.

GC-MS Metabolomic Analysis to Reveal the Metabolites and Biological Pathways Involved in the Developmental Stages and Tissue Response of Panax ginseng

Ginsenosides, the major compounds present in ginseng, are known to have numerous physiological and pharmacological effects. The physiological processes, enzymes and genes involved in ginsenoside synthesis in P. ginseng have been well characterized. However, relatively little information is known about the dynamic metabolic changes that occur during ginsenoside accumulation in ginseng. To explore this topic, we isolated metabolites from different tissues at different growth stages, and identified and characterized them by using gas chromatography coupled with mass spectrometry (GC-MS). The results showed that a total of 30, 16, 20, 36 and 31 metabolites were identified and involved in different developmental stages in leaf, stem, petiole, lateral root and main root, respectively. To investigate the contribution of tissue to the biosynthesis of ginsenosides, we examined the metabolic changes of leaf, stem, petiole, lateral root and main root during five development stages: 1-, 2-, 3-, 4- and 5-years. The score plots of partial least squares-discriminate analysis (PLS-DA) showed clear discrimination between growth stages and tissue samples. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis in the same tissue at different growth stages indicated profound biochemical changes in several pathways, including carbohydrate metabolism and pentose phosphate metabolism, in addition, the tissues displayed significant variations in amino acid metabolism, sugar metabolism and energy metabolism. These results should facilitate further dissection of the metabolic flux regulation of ginsenoside accumulation in different developmental stages or different tissues of ginseng.

Functional regulation of ginsenoside biosynthesis by RNA interferences of a UDP-glycosyltransferase gene in Panax ginseng and Panax quinquefolius

Panax ginseng (Asian ginseng) and Panax quinquefolius (American ginseng) have been used as medicinal and functional herbal remedies worldwide. Different properties of P. ginseng and P. quinquefolius were confirmed not only in clinical findings, but also at cellular and molecular levels. The major pharmacological ingredients of P. ginseng and P. quinquefolius are the triterpene saponins known as ginsenosides. The P. ginseng roots contain a higher ratio of ginsenoside Rg1:Rb1 than that in P. quinquefolius. In ginseng plants, various ginsenosides are synthesized via three key reactions: cyclization, hydroxylation and glycosylation. To date, several genes including dammarenediol synthase (DS), protopanaxadiol synthase and protopanaxatriol synthase have been isolated in P. ginseng and P. quinquefolius. Although some glycosyltransferase genes have been isolated and identified association with ginsenoside synthesis in P. ginseng, little is known about the glycosylation mechanism in P. quinquefolius. In this paper, we cloned and identified a UDP-glycosyltransferase gene named Pq3-O-UGT2 from P. quinquefolius (GenBank accession No. KR106207). In vitro enzymatic activity experiments biochemically confirmed that Pq3-O-UGT2 catalyzed the glycosylation of Rh2 and F2 to produce Rg3 and Rd, and the chemical structure of the products were confirmed susing high performance liquid chromatography electrospray ionization mass spectrometry (HPLC/ESI-MS). High sequence similarity between Pq3-O-UGT2 and PgUGT94Q2 indicated a close evolutionary relationship between P. ginseng and P. quinquefolius. Moreover, we established both P. ginseng and P. quinquefolius RNAi transgenic roots lines. RNA interference of Pq3-O-UGT2 and PgUGT94Q2 led to reduce levels of ginsenoside Rd, protopanaxadiol-type and total ginsenosides. Expression of key genes including protopanaxadiol and protopanaxatriol synthases was up-regulated in RNAi lines, while expression of dammarenediol synthase gene was not obviously increased. These results revealed that P. quinquefolius was more sensitive to the RNAi of Pq3-O-UGT2 and PgUGT94Q2 when compared with P. ginseng.

Transcriptome Sequencing of Gynostemma pentaphyllum to Identify Genes and Enzymes Involved in Triterpenoid Biosynthesis

G. pentaphyllum (Gynostemma pentaphyllum), a creeping herbaceous perennial with many important medicinal properties, is widely distributed in Asia. Gypenosides (triterpenoid saponins), the main effective components of G. pentaphyllum, are well studied. FPS (farnesyl pyrophosphate synthase), SS (squalene synthase), and SE (squalene epoxidase) are the main enzymes involved in the synthesis of triterpenoid saponins. Considering the important medicinal functions of G. pentaphyllum, it is necessary to investigate the transcriptomic information of G. pentaphyllum to facilitate future studies of transcriptional regulation. After sequencing G. pentaphyllum, we obtained 50,654,708 unigenes. Next, we used RPKM (reads per kilobases per million reads) to calculate expression of the unigenes and we performed comparison of our data to that contained in five common databases to annotate different aspects of the unigenes. Finally, we noticed that FPS, SS, and SE showed differential expression of enzymes in DESeq. Leaves showed the highest expression of FPS, SS, and SE relative to the other two tissues. Our research provides transcriptomic information of G. pentaphyllum in its natural environment and we found consistency in unigene expression, enzymes expression (FPS, SS, and SE), and the distribution of gypenosides content in G. pentaphyllum. Our results will enable future related studies of G. pentaphyllum.

Bioactivity of Phytosterols and Their Production in Plant in Vitro Cultures

Phytosterols are a kind of plant metabolite belonging to the triterpene family. These compounds are essential biomolecules for human health, and so they must be taken from foods. β-Sitosterol, campesterol, and stigmasterol are the main phytosterols found in plants. Phytosterols have beneficial effects on human health since they are able to reduce plasma cholesterol levels and have antiinflammatory, antidiabetic, and anticancer activities. However, there are many difficulties in obtaining them, since the levels of these compounds produced from plant raw materials are low and their chemical synthesis is not economically profitable for commercial exploitation. A biotechnological alternative for their production is the use of plant cell and hairy root cultures. This review is focused on the biosynthesis of phytosterols and their function in both plants and humans as well as the different biotechnological strategies to increase phytosterol biosynthesis. Special attention is given to describing new methodologies based on the use of recombinant DNA technology to increase the levels of phytosterols.

Triterpenoid profiling and functional characterization of the initial genes involved in isoprenoid biosynthesis in neem (Azadirachta indica)

BACKGROUND

Neem tree (Azadirachta indica) is one of the richest sources of skeletally diverse triterpenoids and they are well-known for their broad-spectrum pharmacological and insecticidal properties. However, the abundance of Neem triterpenoids varies among the tissues. Here, we delineate quantitative profiling of fifteen major triterpenoids across various tissues including developmental stages of kernel and pericarp, flower, leaf, stem and bark using UPLC-ESI(+)-HRMS based profiling. Transcriptome analysis was used to identify the initial genes involved in isoprenoid biosynthesis. Based on transcriptome analysis, two short-chain prenyltransferases and squalene synthase (AiSQS) were cloned and functionally characterized.

RESULTS

Quantitative profiling revealed differential abundance of both total and individual triterpenoid content across various tissues. RNA from tissues with high triterpenoid content (fruit, flower and leaf) were pooled to generate 79.08 million paired-end reads using Illumina GA ΙΙ platform. 41,140 transcripts were generated by d e novo assembly. Transcriptome annotation led to the identification of the putative genes involved in isoprenoid biosynthesis. Two short-chain prenyltransferases, geranyl diphosphate synthase (AiGDS) and farnesyl diphosphate synthase (AiFDS) and squalene synthase (AiSQS) were cloned and functionally characterized using transcriptome data. RT-PCR studies indicated five-fold and ten-fold higher relative expression level of AiSQS in fruits as compared to leaves and flowers, respectively.

CONCLUSIONS

Triterpenoid profiling indicated that there is tissue specific variation in their abundance. The mature seed kernel and initial stages of pericarp were found to contain the highest amount of limonoids. Furthermore, a wide diversity of triterpenoids, especially C-seco triterpenoids were observed in kernel as compared to the other tissues. Pericarp, flower and leaf contained mainly ring-intact triterpenoids. The initial genes such as AiGDS, AiFDS and AiSQS involved in the isoprenoids biosynthesis have been functionally characterized. The expression levels of AiFDS and AiSQS were found to be in correlation with the total triterpenoid content in individual tissues.

Biosynthesis and biotechnological production of ginsenosides

Medicinal plants are essential for improving human health, and around 75% of the population in developing countries relies mainly on herb-based medicines for health care. As the king of herb plants, ginseng has been used for nearly 5,000 years in the oriental and recently in western medicines. Among the compounds studied in ginseng plants, ginsenosides have been shown to have multiple medical effects such as anti-oxidative, anti-aging, anti-cancer, adaptogenic and other health-improving activities. Ginsenosides belong to a group of triterpene saponins (also called ginseng saponins) that are found almost exclusively in Panax species and accumulated especially in the plant roots. In this review, we update the conserved and diversified pathway/enzyme biosynthesizing ginsenosides which have been presented. Particularly, we highlight recent milestone works on functional characterization of key genes dedicated to the production of ginsenosides, and their application in engineering plants and yeast cells for large-scale production of ginsenosides.