Biotic elicitation of ginsenoside metabolism of mutant adventitious root culture in Panax ginseng

Unleashing plant synthetic capacity: navigating regulatory mechanisms for enhanced bioproduction and secondary metabolite discovery

Plant natural products (PNPs) hold significant pharmaceutical importance. The sessile nature of plants has led to the evolution of chemical defense mechanisms over millions of years to combat environmental challenges, making it a crucial and essential defense weapon. Despite their importance, the abundance of these bioactive molecules in plants is typically low, and conventional methods are time-consuming for enhancing production. Moreover, there is a pressing need for novel drug leads, exemplified by the shortage of antibiotics and anticancer drugs. Understanding how plants respond to stress and regulate metabolism to produce these molecules presents an opportunity to explore new avenues for discovering compounds that are typically under the detection limit or not naturally produced. Additionally, this knowledge can contribute to the advancement of plant engineering, enabling the development of new chassis for the biomanufacturing of these valuable molecules. In this perspective, we explore the intricate regulation of PNP biosynthesis in plants, and discuss the biotechnology strategies that have been and can be utilized for the discovery and production enhancement of PNPs in plants.

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.

A systematic review of ginsenoside biosynthesis, spatiotemporal distribution, and response to biotic and abiotic factors in American ginseng

American ginseng (Panax quinquefolius) has gained recognition as a medicinal and functional food homologous product with several pharmaceutical, nutritional, and industrial applications. However, the key regulators involved in ginsenoside biosynthesis, the spatiotemporal distribution characteristics of ginsenosides, and factors influencing ginsenosides are largely unknown, which make it challenging to enhance the quality and chemical extraction processes of the cultivated American ginseng. This review presents an overview of the pharmacological effects, biosynthesis and spatiotemporal distribution of ginsenosides, with emphasis on the impacts of biotic and abiotic factors on ginsenosides in American ginseng. Modern pharmacological studies have demonstrated that American ginseng has neuroprotective, cardioprotective, antitumor, antidiabetic, and anti-obesity effects. Additionally, most genes involved in the upregulation of ginsenoside biosynthesis have been identified, while downstream regulators (OSCs, CYP450, and UGTs) require further investigation. Futhermore, limited knowledge exists regarding the molecular mechanisms of the impact of biotic and abiotic factors on ginsenosides. Notably, the nonmedicinal parts of American ginseng, particularly its flowers, fibrous roots, and leaves, exhibit higher ginsenoside content than its main roots and account for a considerable amount of weight in the whole plant, representing promising resources for ginsenosides. Herein, the prospects of molecular breeding and metabolic engineering based on multi-omics to improve the unstable quality of cultivated American ginseng and the shortage of ginsenosides are proposed. This review highlights the gaps in the current research on American ginseng and proposes solutions to address these limitations, providing a guide for future investigations into American ginseng ginsenosides.

Improving Flavonoid Accumulation of Bioreactor-Cultured Adventitious Roots in Oplopanax elatus Using Yeast Extract

Oplopanax elatus is an endangered medicinal plant, and adventitious root (AR) culture is an effective way to obtain its raw materials. Yeast extract (YE) is a lower-price elicitor and can efficiently promote metabolite synthesis. In this study, the bioreactor-cultured O. elatus ARs were treated with YE in a suspension culture system to investigate the elicitation effect of YE on flavonoid accumulation, serving for further industrial production. Among YE concentrations (25-250 mg/L), 100 mg/L YE was the most suitable for increasing the flavonoid accumulation. The ARs with various ages (35-, 40-, and 45-day-old) responded differently to YE stimulation, where the highest flavonoid accumulation was found when 35-day-old ARs were treated with 100 mg/L YE. After YE treatment, the flavonoid content increased, peaked at 4 days, and then decreased. By comparison, the flavonoid content and antioxidant activities in the YE group were obviously higher than those in the control. Subsequently, the flavonoids of ARs were extracted by flash extraction, where the optimized extraction process was: 63% ethanol, 69 s of extraction time, and a 57 mL/g liquid-material ratio. The findings provide a reference for the further industrial production of flavonoid-enriched O. elatus ARs, and the cultured ARs have potential application for the future production of products.

Engineering of triterpene metabolism and overexpression of the lignin biosynthesis gene PAL promotes ginsenoside Rg3 accumulation in ginseng plant chassis

The ginsenoside Rg₃ found in Panax species has extensive pharmacological properties, in particular anti-cancer effects. However, its natural yield in Panax plants is limited. Here, we report a multi-modular strategy to improve yields of Rg₃ in a Panax ginseng chassis, combining engineering of triterpene metabolism and overexpression of a lignin biosynthesis gene, phenylalanine ammonia lyase (PAL). We first performed semi-rational design and site mutagenesis to improve the enzymatic efficiency of Pq3-O-UGT2, a glycosyltransferase that directly catalyzes the biosynthesis of Rg₃ from Rh₂ . Next, we used clustered regularly interspaced palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) gene editing to knock down the branch pathway of protopanaxatriol-type ginsenoside biosynthesis to enhance the metabolic flux of the protopanaxadiol-type ginsenoside Rg₃ . Overexpression of PAL accelerated the formation of the xylem structure, significantly improving ginsenoside Rg₃ accumulation (to 6.19-fold higher than in the control). We combined overexpression of the ginsenoside aglycon synthetic genes squalene epoxidase, Pq3-O-UGT2, and PAL with CRISPR/Cas9-based knockdown of CYP716A53v2 to improve ginsenoside Rg₃ accumulation. Finally, we produced ginsenoside Rg₃ at a yield of 83.6 mg/L in a shake flask (7.0 mg/g dry weight, 21.12-fold higher than with wild-type cultures). The high-production system established in this study could be a potential platform to produce the ginsenoside Rg₃ commercially for pharmaceutical use.

Phytochemistry of ginsenosides: Recent advancements and emerging roles

Ginsenosides, a group of tetracyclic saponins, accounts for the nutraceutical and pharmaceutical relevance of the ginseng (Panax sp.) herb. Owing to the associated therapeutic potential of ginsenosides, their demand has been increased significantly in the last two decades. However, a slow growth cycle, low seed production, and long generation time of ginseng have created a gap between the demand and supply of ginsenosides. The biosynthesis of ginsenosides involves an intricate network of pathways with multiple oxidation and glycosylation reactions. However, the exact functions of some of the associated genes/proteins are still not completely deciphered. Moreover, ginsenoside estimation and extraction using analytical techniques are not feasible with high efficiency. The present review is a step forward in recapitulating the comprehensive aspects of ginsenosides including their distribution, structural diversity, biotransformation, and functional attributes in both plants and animals including humans. Moreover, ginsenoside biosynthesis in the potential plant sources and their metabolism in the human body along with major regulators and stimulators affecting ginsenoside biosynthesis have also been discussed. Furthermore, this review consolidates biotechnological interventions to enhance the biosynthesis of ginsenosides in their potential sources and advancements in the development of synthetic biosystems for efficient ginsenoside biosynthesis to meet their rising industrial demands.

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.

In vitro adventitious roots: a non-disruptive technology for the production of phytoconstituents on the industrial scale

The current trends of consumer-driven demands for natural therapeutics and the availability of evidence-based phytopharmaceuticals from traditional knowledge has once again brought the medicinal plants into forefront of health. In 2019, World Health Organization global report on traditional and complementary medicine has also substantiated the revival of herbal medicine including its convergence with conventional medicine for the management and prevention of diseases. It means these industries need plenty of plant materials to meet the unprecedented demands of herbal formulations. However, it is pertinent to mention here that around 70-80% medicinal plants are sourced from the wild and most of such highly acclaimed plants are listed under Rare, Endangered and Threatened species by IUCN. Additionally, over 30% traditional health formulations are based on underground plant parts, which lead to the uprooting of plants. Overharvesting from limited plant populations, meager conventional cultivation and a rising fondness for natural products exerting enormous pressure on natural habitats. Therefore, the nondestructive means of phytochemical production employing biotechnological tools could be used for sustainable production and consumption patterns. In recent years, a number of reports described the use of adventitious roots induced under in vitro conditions for the extraction of phytochemicals on a sustainable basis. In this article, efforts are made to review recent developments in this area as well as understand the induction mechanisms of adventitious roots, their in vitro cultivation, probable factors that affect the growth and metabolite production, and assess the possibility of industrial scale production to meet the rising demands of natural herbs.

Penicillium sp. YJM-2013 induces ginsenosides biosynthesis in Panax ginseng adventitious roots by inducing plant resistance responses

Objective

Fusarium oxysporum is a common pathogenic fungus in ginseng cultivation. Both pathogens and antagonistic fungi have been reported to induce plant resistance responses, thereby promoting the accumulation of secondary metabolites. The purpose of this experiment is to compare the advantages of one of the two fungi, in order to screen out more effective elicitors. The mechanism of fungal elicitor-induced plant resistance response is supplemented.

Methods

A gradient dilution and the dural culture were carried out to screen strains. The test strain was identified by morphology and 18 s rDNA. The effect of different concentrations (0, 50, 100, 200, 400 mg/L) of Penicillium sp. YJM-2013 and F. oxysporum on fresh weight and ginsenosides accumulation were tested. Signal molecules transduction, expression of transcription factors and functional genes were investigated to study the induction mechanism of fungal elicitors.

Results

Antagonistic fungi of F. oxysporum was identified as Penicillium sp. YJM-2013, which reduced root biomass. The total ginsenosides content of Panax ginseng adventitious roots reached the maximum (48.95 ± 0.97 mg/g) treated with Penicillium sp. YJM-2013 at 200 mg/L, higher than control by 2.59-fold, in which protopanoxadiol-type ginsenosides (PPD) were increased by 4.57 times. Moreover, Penicillium sp. YJM-2013 activated defense signaling molecules, up-regulated the expression of PgWRKY 1, 2, 3, 5, 7, 9 and functional genes in ginsenosides synthesis.

Conclusion

Compared with the pathogenic fungi F. oxysporum, antagonistic fungi Penicillium sp. YJM-2013 was more conducive to the accumulation of ginsenosides in P. ginseng adventitious roots. Penicillium sp. YJM-2013 promoted the accumulation of ginsenosides by intensifying the generation of signal molecules, activating the expression of transcription factors and functional genes.

Biotic elicitors enhance diosgenin production in Helicteres isora L. suspension cultures via up-regulation of CAS and HMGR genes

In an attempt to find an alternative and potent source of diosgenin, a steroidal saponin in great demand for its pharmaceutical importance, Helicteres isora suspension cultures were explored for diosgenin extraction. The effect of biotic elicitors on the biosynthesis of diosgenin, in suspension cultures of H. isora was studied. Bacterial as well as fungal elicitors such as Escherichia coli, Bacillus subtilis, Saccharomyces cerevisiae and Aspergillus niger were applied at varying concentrations to investigate their effects on diosgenin content. The HPLC based quantification of the treated samples proved that amongst the biotic elicitors, E. coli (1.5%) proved best with a 9.1-fold increase in diosgenin content over respective control cultures. Further, the scaling-up of the suspension culture to shake-flask and ultimately to bioreactor level were carried out for production of diosgenin. During all the scaling-up stages, diosgenin yield obtained was in the range between 7.91 and 8.64 mg l^-1, where diosgenin content was increased with volume of the medium. The quantitative real-time PCR (qRT-PCR) analysis showed biotic elicitors induced the expression levels of regulatory genes in diosgenin biosynthetic pathway, the 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) and cycloartenol synthase (CAS), which can be positively correlated with elicited diosgenin contents in those cultures. The study holds significance as H. isora represents a cleaner and easy source of diosgenin where unlike other traditional sources, it is not admixed with other steroidal saponins, and the scaled-up levels of diosgenin achieved herein have the potential to be explored commercially.

Quality evaluation of Panax ginseng adventitious roots based on ginsenoside constituents, functional genes, and ferric-reducing antioxidant power

In the study, six adventitious root lines of Panax ginseng have been successfully established. HPLC-ESI-MS analysis showed that 20 ginsenosides were identified in root lines, notoginsenoside Fa and notoginsenoside R₂ were not found in AR lines. In AR lines, the highest accumulation of total ginsenosides was obtained in five-year main AR (24.87 mg/g). Principal component analysis classified root lines into three groups. Five-year ginseng was mostly similar with five-year main AR, five-year rootlet AR, and four-year rootlet AR in ginsenosides composition of group 1. Besides, gene expressions were consistent with the production of total ginsenosides, and correlation analysis revealed that total ginsenosides biosynthesis was significantly positively correlated with the gene expression of dammarenediol synthase. Five-year rootlet AR showed the highest activity on ferric-reducing antioxidant power test among samples. It provides a scientific evidence for the further exploitation and large-scale production of P. ginseng. PRACTICAL APPLICATIONS: This study provides valuable information for the commercial scale culture of ginseng adventitious roots. This report combines morphology, ginsenoside composition and content, gene expression, and ferric-reducing antioxidant power test to evaluate the quality of P. ginseng adventitious root, and combined with principal component analysis to screen out the high yield and stable ginseng adventitious roots. It would be profitable to use adventitious root culture of P. ginseng instead of field cultivation.

Effect of temperature on morphology, ginsenosides biosynthesis, functional genes, and transcriptional factors expression in Panax ginseng adventitious roots

This study researched the effect of temperature on growth and ginsenosides accumulation in adventitious root cultures of Panax ginseng. Results showed that the ginseng adventitious roots growth and differentiation ability could be affected faced with different incubation temperatures (15, 20, 25, and 30°C for 35 days). Besides, the research also demonstrated that low-temperature stimulation could promote the accumulation of ginsenosides and the content of total ginsenosides increased by 2.53 times at 10°C-7d (10°C for 7 days and then transferred to 25°C for 28 days) compared with that at 25°C. Moreover, the transcriptional levels of functional genes and PgWRKYs were analyzed by this study and the correlation analysis showed that GPS, SS, CYP716A47, CYP716A53v2, UGT74AE2, UGT94Q2, PgWRKY1, PgWRKY3, and PgWRKY8 were significantly correlated with total ginsenosides content. Furthermore, HPLC-ESI-MSⁿ analyzed that Malonyl-Rb₁ only existed in 10°C-7d group. PRACTICAL APPLICATIONS: The survey showed that after a certain time of stimulating P. ginseng adventitious roots at low temperature, the accumulation of ginsenosides could be enhanced as their expression of related genes were regulated. It provides a theoretical foundation for the mass production of ginsenosides by controlling the temperature conditions of P. ginseng adventitious roots.