Optimization of methyl jasmonate and β-cyclodextrin for enhanced production of taraxerol and taraxasterol in (Taraxacum officinale Weber) cultures

Effect of Inoculum Size and Age, and Sucrose Concentration on Cell Growth to Promote Metabolites Production in Cultured Taraxacum officinale (Weber) Cells

Pentacyclic triterpenes, including lupeol, α- amyrin, and β-amyrin, present a large range of biological activities including anti-inflammatory, anti-cancer, and gastroprotective properties. The phytochemistry of dandelion (Taraxacum officinale) tissues has been widely described. Plant biotechnology offers an alternative for secondary metabolite production and several active plant ingredients are already synthesized through in vitro cultures. This study aimed to establish a suitable protocol for cell growth and to determine the accumulation of α-amyrin and lupeol in cell suspension cultures of T. officinale under different culture conditions. To this end, inoculum density (0.2% to 8% (w/v)), inoculum age (2- to 10-week-old), and carbon source concentration (1%, 2.3%, 3.2%, and 5.5% (w/v)) were investigated. Hypocotyl explants of T. officinale were used for callus induction. Age, size, and sucrose concentrations were statistically significant in cell growth (fresh and dry weight), cell quality (aggregation, differentiation, viability), and triterpenes yield. The best conditions for establishing a suspension culture were achieved by using a 6-week-old callus at 4% (w/v) and 1% (w/v) of sucrose concentration. Results indicate that 0.04 (±0.02) α-amyrin and 0.03 (±0.01) mg/g lupeol can be obtained in suspension culture under these starting conditions at the 8th week of culture. The results of the present study provide a backdrop for future studies in which an elicitor could be incorporated to increase the large-scale production of α-amyrin and lupeol from T. officinale.

A jasmonate-responsive bHLH transcription factor TaMYC2 positively regulates triterpenes biosynthesis in Taraxacum antungense Kitag

Dandelion is a well-known traditional medical herb, also used as functional food. Dandelion possesses many medical properties, such as anti-bacterial and antioxidant activity and contains a variety of triterpenes, such as α-amyrin, β-amyrin, taraxerol and taraxasterol. In this study, we found that triterpenes biosynthesis was promoted by methyl jasmonate (MeJA), while the transcriptional mechanism underlying triterpenes biosynthesis was rarely investigated. Here, a MeJA-induced bHLH transcription factor TaMYC2 was identified. The content of taraxasterol and taraxerol in dandelion was obviously enhanced in overexpression TaMYC2 transgenic lines and expression level of the squalene synthase gene (TaSS) was elevated to about 3-5 folds compared with the control lines. Dual-LUC, Y1H and EMSA experiments revealed that TaMYC2 bound to the E-box motif in the promoter of TaSS and activated its transcription. Taken together, this study suggested that TaMYC2 acted as a positive regulator for bioengineering approaches to produce high content triterpenes-producing dandelions.

Cyclodextrins Increase Triterpene Production in Solanum lycopersicum Cell Cultures by Activating Biosynthetic Genes

In this work, Solanum lycopersicum cv. Micro-Tom suspension-cultured cells were used to analyze the effect of different elicitors including β-cyclodextrins (CD), methyl jasmonate (MJ), β-glucan (Glu) and 3-hexenol (Hex) separately and the combined treatments of CD + MJ, CD + glu and CD + Hex on triterpene compound production after 24, 72 and 96 h. Moreover, we studied the changes induced by elicitors in the expression of key biosynthetic genes to elucidate the regulation of the triterpene biosynthetic pathway. The relative abundance of the triterpene compounds identified in the extracellular medium after elicitation (squalene, fucosterol, avenasterol, β-sitosterol, cycloartenol and taraxasterol) was determined by gas chromatography coupled to mass spectrometry, and the expression level of genes in treated-cells was analyzed by real-time quantitative polymerase chain reaction (qRT-PCR). Results showed that, in CD-treated cells (CD, CD + MJ, CD + Glu, CD + Hex), specialized metabolites were accumulated mainly in the extracellular medium after 72 h of elicitation. Moreover, qRT-PCR analysis revealed that the highest triterpene levels in CD-treated cells (CD, CD + MJ, CD + Glu, CD + Hex) were highly correlated with the expression of cycloartenol synthase, 3-hydroxy-3-methylglutaryl-CoA reductase and squalene epoxidase genes at 24 h of treatment, whereas the expression of sterol methyltransferase was increased at 72 h. According to our findings, CD acts as a true elicitor of triterpene biosynthesis and can promote the release of bioactive compounds from the tomato cells into the extracellular medium. The results obtained provide new insights into the regulation of the triterpene metabolic pathway, which might be useful for implementing metabolic engineering techniques in tomato.

The Biosynthesis and Medicinal Properties of Taraxerol

Taraxerol is a pentacyclic triterpenoid that is actively produced by some higher plants as part of a defense mechanism. The biosynthesis of taraxerol in plants occurs through the mevalonate pathway in the cytosol, in which dimethylallyl diphosphate (DMAPP) and isopentyl pyrophosphate (IPP) are first produced, followed by squalene. Squalene is the primary precursor for the synthesis of triterpenoids, including taraxerol, β-amyrin, and lupeol, which are catalyzed by taraxerol synthase. Taraxerol has been extensively investigated for its medicinal and pharmacological properties, and various biotechnological approaches have been established to produce this compound using in vitro techniques. This review provides an in-depth summary of the hypothesized taraxerol biosynthetic pathway, the medicinal properties of taraxerol, and recent developments on tissue culture for the in vitro production of taraxerol.

The Role of Cyclodextrins in the Design and Development of Triterpene-Based Therapeutic Agents

Triterpenic compounds stand as a widely investigated class of natural compounds due to their remarkable therapeutic potential. However, their use is currently being hampered by their low solubility and, subsequently, bioavailability. In order to overcome this drawback and increase the therapeutic use of triterpenes, cyclodextrins have been introduced as water solubility enhancers; cyclodextrins are starch derivatives that possess hydrophobic internal cavities that can incorporate lipophilic molecules and exterior surfaces that can be subjected to various derivatizations in order to improve their biological behavior. This review aims to summarize the most recent achievements in terms of triterpene:cyclodextrin inclusion complexes and bioconjugates, emphasizing their practical applications including the development of new isolation and bioproduction protocols, the elucidation of their underlying mechanism of action, the optimization of triterpenes’ therapeutic effects and the development of new topical formulations.

Engineering Considerations to Produce Bioactive Compounds from Plant Cell Suspension Culture in Bioreactors

The large-scale production of plant-derived secondary metabolites (PDSM) in bioreactors to meet the increasing demand for bioactive compounds for the treatment and prevention of degenerative diseases is nowadays considered an engineering challenge due to the large number of operational factors that need to be considered during their design and scale-up. The plant cell suspension culture (CSC) has presented numerous benefits over other technologies, such as the conventional whole-plant extraction, not only for avoiding the overexploitation of plant species, but also for achieving better yields and having excellent scaling-up attributes. The selection of the bioreactor configuration depends on intrinsic cell culture properties and engineering considerations related to the effect of operating conditions on thermodynamics, kinetics, and transport phenomena, which together are essential for accomplishing the large-scale production of PDSM. To this end, this review, firstly, provides a comprehensive appraisement of PDSM, essentially those with demonstrated importance and utilization in pharmaceutical industries. Then, special attention is given to PDSM obtained out of CSC. Finally, engineering aspects related to the bioreactor configuration for CSC stating the effect of the operating conditions on kinetics and transport phenomena and, hence, on the cell viability and production of PDSM are presented accordingly. The engineering analysis of the reviewed bioreactor configurations for CSC will pave the way for future research focused on their scaling up, to produce high value-added PDSM.

Isolation, expression, and functional analysis of the geranylgeranyl pyrophosphate synthase (GGPPS) gene from Liriodendron tulipifera

Terpenoids are important secondary metabolites in plants and are involved in stress responses and pollinator attraction. Geranylgeranyl pyrophosphate synthase (GGPPS) is a key synthase in the 2C-methyl-D-erythritol-4-phosphate (MEP) pathway of terpenoid synthesis, catalyzing the synthesis of diterpenoids. Liriodendron tulipifera is a nectar plant in North America. Little is known about the key genes involved in the biosynthetic pathways of terpenoids, the precursors of most compounds related to nectar, fragrance and coloring in flowers in L. tulipifera. In this study, the LtuGGPPS2 gene and its promoter (LtuGGPPS2-pro) were cloned from L. tulipifera. The results of sequence alignment showed that the LtuGGPPS2 gene is highly homologous to GGPPS genes of other plants. Subcellular localization analysis showed that the LtuGGPPS2 protein localizes to chloroplasts, suggesting that the LtuGGPPS2 gene is probably related to carotenoid and chlorophyll synthesis. Based on tissue expression profiles revealed by RT-qPCR, the expression level of the LtuGGPPS2 gene was highest in petals. These results were consistent with the changes in volatile and nonvolatile terpenoids in the flowers of L. tulipifera. GUS staining to examine the LtuGGPPS2 promoter indicated that it is responsive to hormones. Overexpression of the LtuGGPPS2 gene increased the carotenoid content and GGPPS enzyme activity in Arabidopsis thaliana, indicating that LtuGGPPS2 is the key terpenoid synthase in the flowers of L. tulipifera. Our findings lay a foundation for further functional analysis of the LtuGGPPS2 gene and deeper investigation of the terpenoid biosynthetic pathway in L. tulipifera.

Methyl Jasmonate and Methyl-β-Cyclodextrin Individually Boost Triterpenoid Biosynthesis in Chlamydomonas Reinhardtii UVM4

The commercialisation of valuable plant triterpenoids faces major challenges, including low abundance in natural hosts and costly downstream purification procedures. Endeavours to produce these compounds at industrial scale using microbial systems are gaining attention. Here, we report on a strategy to enrich the biomass of the biotechnologically-relevant Chlamydomonas reinhardtii strain UVM4 with valuable triterpenes, such as squalene and (S)-2,3-epoxysqualene. C. reinhardtii UVM4 was subjected to the elicitor compounds methyl jasmonate (MeJA) and methyl-β-cyclodextrine (MβCD) to increase triterpene yields. MeJA treatment triggered oxidative stress, arrested growth, and altered the photosynthetic activity of the cells, while increasing squalene, (S)-2,3-epoxysqualene, and cycloartenol contents. Applying MβCD to cultures of C. reinhardtii lead to the sequestration of the two main sterols (ergosterol and 7-dehydroporiferasterol) into the growth medium and the intracellular accumulation of the intermediate cycloartenol, without compromising cell growth. When MβCD was applied in combination with MeJA, it counteracted the negative effects of MeJA on cell growth and physiology, but no synergistic effect on triterpene yield was observed. Together, our findings provide strategies for the triterpene enrichment of microalgal biomass and medium.

Biotechnological approaches to the production of plant-derived promising anticancer agents: An update and overview

The plant kingdom is a rich source of bioactive compounds, many of which have been used since pre-history for their therapeutic properties to treat a range of illnesses. These metabolites have recently attracted attention to their antineoplastic activities to treat various cancers relying on different mechanisms. Some of these molecules are glycosides, which have proven useful as anti-cancer agents, namely podophyllotoxin (PPT) anaryltetralin lignan or alkaloids. There are three primary forms of alkaloids, such as indole alkaloids (vincristine and vinblastine from Catharanthus roseus), quinoline alkaloid (camptothecin from Camptotheca acuminata), and diterpenoid alkaloid (taxol and it's analogous from Taxus and Corylus species). This review considers various plant biotechnology approaches used to enhance the production of these anticancer molecules in different species. In this regard, many in vitro culture techniques such as stimulation of suspension culture and hairy roots are being used to investigate the effects of plant growth regulators and elicitors on various explants.

Plant tissue culture as a perpetual source for production of industrially important bioactive compounds

Plants have been used throughout the world for its medicinal powers since ancient time. The pharmacological properties of plants are based on their phytochemical components especially the secondary metabolites which are outstanding sources of value added bioactive compounds. Secondary metabolites have complex chemical composition and are produced in response to various forms of stress to perform different physiological tasks in plants. They are used in pharmaceutical industries, cosmetics, dietary supplements, fragrances, flavors, dyes, etc. Extended use of these metabolites in various industrial sectors has initiated a need to focus research on increasing the production by employing plant tissue culture (PTC) techniques and optimizing their large scale production using bioreactors. PTC techniques being independent of climatic and geographical conditions will provide an incessant, sustainable, economical and viable production of secondary metabolites. This review article intends to assess the advantages of using plant tissue culture, distribution of important secondary metabolites in plant families, strategies involved for optimal metabolite production and the industrial importance of selected secondary metabolites.

The enzymes OSC1 and CYP716A263 produce a high variety of triterpenoids in the latex of Taraxacum koksaghyz

Only very little is known about the resin composition of natural rubber from the dandelion species Taraxacum koksaghyz, thus its full characterization could provide new insights into how the isoprenoid end-products influence the physical properties of natural rubber, and this resin might be a good source of highly diverse triterpenoids. Here, we present a comprehensive analysis of the triterpenoid composition in an acetone extract and identified 13 triterpenes and triterpenoids also including the so far unknown pentacyclic compounds lup-19(21)-en-3-ol (1) and its ketone lup-19(21)-en-3-one (2). We purified single triterpenes from the acetone extract by developing a two-step HPLC system that is adapted to the structural differences of the described triterpenoids. Furthermore, we isolated six different oxidosqualene cyclases (OSCs) and two P450 enzymes, and we functionally characterized TkOSC1 and CYP716A263 in Nicotiana benthamiana and Saccharomyces cerevisiae in detail. TkOSC1 is a multifunctional OSC that was capable of synthesizing at least four of the latex-predominant pentacyclic triterpenes (taraxasterol, α-, β-amyrin and lup-19(21)-en-3-ol) while CYP716A263 oxidized pentacyclic triterpenes at the C-3 position. The identified enzymes responsible for biosynthesis and modification of pentacyclic triterpenes in T. koksaghyz latex may represent excellent tools for bioengineering approaches to produce pentacyclic triterpenes heterologously.

Inhibitory effects of taraxasterol and aqueous extract of Taraxacum officinale on calcium oxalate crystallization: in vitro study

Objective: We investigated and compared the effects of taraxasterol, aqueous extract of T. officinale (AET) aerial part, and potassium citrate (PC) on calcium oxalate (CaOx) crystallization in vitro.

Materials and methods: CaOx crystallization was induced by adding sodium oxalate to synthetic urine. Taraxasterol (2.5, 5, 7.5 and 12.5 μg/mL), extract (1, 2, 4 and 8 mg/mL), and PC (100, 150, 200 and 350 mg/mL) were subjected to anti-crystallization activities. The absorbance and %inhibition of nucleation of CaOx crystals were evaluated by spectrophotometer at 2, 4, 6, 8, 10, 20, 30, 40, 50 and 60 min and the number and morphology of crystals were studied by light microscopy after 60 min.

Results: Presence of taraxasterol, extract and PC decreased absorbance in experimental samples compared to control, significantly. The nucleation of crystals is inhibited by taraxasterol, extract, and PC (26–64, 55–63 and 60–70%, respectively). The number of CaOx crystals were decreased in presence of taraxasterol (p < .01), extract (p < .001), and PC (p < .001) in a dose-dependent manner. Presence of taraxasterol, extract, and PC decreased the number of CaC₂O₄ monohydrate, while increased CaC₂O₄ dihydrate crystals, significantly. Also, the diameter of CaC₂O₄ dihydrate crystals was decreased in presence of taraxasterol, extract and PC, significantly.

Conclusions: This research indicated that taraxasterol and extract have anti-crystallization activities and effectiveness of the extract is more potent than taraxasterol. It could be because of another constituent in the extract with the synergistic effect.

Isoprenoid biosynthesis in dandelion latex is enhanced by the overexpression of three key enzymes involved in the mevalonate pathway

BACKGROUND

Latex from the dandelion species Taraxacum brevicorniculatum contains many high-value isoprenoid end products, e.g. triterpenes and polyisoprenes such as natural rubber. The isopentenyl pyrophosphate units required as precursors for these isoprenoids are provided by the mevalonate (MVA) pathway. The key enzyme in this pathway is 3-hydroxy-methyl-glutaryl-CoA reductase (HMGR) and its activity has been thoroughly characterized in many plant species including dandelion. However, two enzymes acting upstream of HMGR have not been characterized in dandelion latex: ATP citrate lyase (ACL), which provides the acetyl-CoA utilized in the MVA pathway, and acetoacetyl-CoA thiolase (AACT), which catalyzes the first step in the pathway to produce acetoacetyl-CoA. Here we isolated ACL and AACT genes from T. brevicorniculatum latex and characterized their expression profiles. We also overexpressed the well-characterized HMGR, ACL and AACT genes from Arabidopsis thaliana in T. brevicorniculatum to determine their impact on isoprenoid end products in the latex.

RESULTS

The spatial and temporal expression profiles of T. brevicorniculatum ACL and AACT revealed their pivotal role in the synthesis of precursors necessary for isoprenoid biosynthesis in latex. The overexpression of A. thaliana ACL and AACT and HMGR in T. brevicorniculatum latex resulted in the accumulation of all three enzymes, increased the corresponding enzymatic activities and ultimately increased sterol levels by ~5-fold and pentacyclic triterpene and cis-1,4-isoprene levels by ~2-fold. Remarkably high levels of the triterpene precursor squalene were also detected in the triple-transgenic lines (up to 32 mg/g root dry weight) leading to the formation of numerous lipid droplets which were observed in root cross-sections.

CONCLUSIONS

We could show the effective expression of up to three transgenes in T. brevicorniculatum latex which led to increased enzymatic activity and resulted in high level squalene accumulation in the dandelion roots up to an industrially relevant amount. Our data provide insight into the regulation of the MVA pathway in dandelion latex and can be used as a basis for metabolic engineering to enhance the production of isoprenoid end products in this specialized tissue.