Yeast extract and methyl jasmonate-induced silymarin production in cell cultures of Silybum marianum (L.) Gaertn

Adding yeast extract to culture medium enhances replication of the avian coronavirus infectious bronchitis virus in chicken embryo kidney cells

Infectious bronchitis virus (IBV), an avian coronavirus, can be isolated and cultured in tracheal organ cultures (TOCs), embryonated eggs and cell cultures, the first two of which are commonly used for viral isolation. Previous studies have suggested that foetal bovine serum (FBS) can inhibit coronavirus replication in cell cultures. In this study, the replication of IBV in chicken embryo kidney (CEK) cell cultures and the Leghorn hepatocellular carcinoma (LMH) cell line was assessed using two different cell culture media containing FBS or yeast extract (YE) and two different IBV strains. The highest concentrations of viral genomes were observed when the cell culture medium (CEK) contained YE. Similar results were observed in LMH cells. Examination of the infectivity by titration demonstrated that the cell lysate from CEK cell cultures in a medium including YE contained a higher median embryo infectious dose than that from CEK cell cultures in a medium containing FBS. These results indicate that improved replication of IBV in cell cultures can be achieved by replacing FBS with YE in the cell culture medium.

Influence of Abiotic and Biotic Elicitors on Organogenesis, Biomass Accumulation, and Production of Key Secondary Metabolites in Asteraceae Plants

The medicinal plants of the Asteraceae family are a valuable source of bioactive secondary metabolites, including polyphenols, phenolic acids, flavonoids, acetylenes, sesquiterpene lactones, triterpenes, etc. Under stressful conditions, the plants develop these secondary substances to carry out physiological tasks in plant cells. Secondary Asteraceae metabolites that are of the greatest interest to consumers are artemisinin (an anti-malarial drug from Artemisia annua L.-sweet wormwood), steviol glycosides (an intense sweetener from Stevia rebaudiana Bert.-stevia), caffeic acid derivatives (with a broad spectrum of biological activities synthesized from Echinacea purpurea (L.) Moench-echinacea and Cichorium intybus L.-chicory), helenalin and dihydrohelenalin (anti-inflammatory drug from Arnica montana L.-mountain arnica), parthenolide ("medieval aspirin" from Tanacetum parthenium (L.) Sch.Bip.-feverfew), and silymarin (liver-protective medicine from Silybum marianum (L.) Gaertn.-milk thistle). The necessity to enhance secondary metabolite synthesis has arisen due to the widespread use of these metabolites in numerous industrial sectors. Elicitation is an effective strategy to enhance the production of secondary metabolites in in vitro cultures. Suitable technological platforms for the production of phytochemicals are cell suspension, shoots, and hairy root cultures. Numerous reports describe an enhanced accumulation of desired metabolites after the application of various abiotic and biotic elicitors. Elicitors induce transcriptional changes in biosynthetic genes, leading to the metabolic reprogramming of secondary metabolism and clarifying the mechanism of the synthesis of bioactive compounds. This review summarizes biotechnological investigations concerning the biosynthesis of medicinally essential metabolites in plants of the Asteraceae family after various elicitor treatments.

Metabolomics Reveals Rubiadin Accumulation and the Effects of Methyl Jasmonate Elicitation in Damnacanthus major Calli

Callus suspension techniques have been considered attractive for improving bioactive metabolite productivity; methyl jasmonate (MeJA) is a widely used elicitor for stimulating synthetic pathways. In this study, a multivariate analysis-based metabolomics approach was employed to investigate the primary and specialized metabolites in the leaves, unelicited calli, and 100 or 200 μM MeJA elicited calli of Damnacanthus major. Rubiadin, a powerful anthraquinone with various therapeutic properties, was only identified in D. major calli, accumulating in a MeJA elicitation concentration-dependent manner. Callus cultures also contained high levels of amino acids, sugars, and phenolic compounds, indicating energy metabolism and metabolic adaptation responses for proliferation and stabilization. Regarding MeJA application, elicited calli contained higher amounts of quinic acid, kaempferol, and glucose with lower amounts of sucrose and raffinose than those in the unelicited control, which were closely related to protective mechanisms against MeJA. Moreover, excessive elicitation increased the asparagine, fructose, and raffinose levels and decreased the glucose and sucrose levels, which was ascribed to increased activation of the aminoacyl-tRNA biosynthesis pathway and wider utilization of glucose than of fructose after sucrose degradation. These results will be useful for optimizing plant cell culture techniques to achieve high production rates for valuable specialized metabolites.

Improved Chrysin Production by a Combination of Fermentation Factors and Elicitation from Chaetomium globosum

Flavonoids encompass a heterogeneous group of secondary metabolites with exceptional health benefits. Chrysin, a natural dihydroxyflavone, possesses numerous bioactive properties, such as anticancer, antioxidative, antidiabetic, anti-inflammatory, etc. However, using traditional sources of chrysin involves extracting honey from plants, which is non-scalable, unsustainable, and depends on several factors, including geography, climatic conditions, and the season, which limits its production at a larger scale. Recently, microbial production of desirable metabolites has garnered attention due to the cost-effectiveness, easy scale-up, sustainability, and low emission of waste. We previously reported for the first time the chrysin-producing marine endophytic fungus Chaetomium globosum, associated with a marine green alga. To extend our understanding of chrysin biosynthesis in C. globosum, in the present study, we have assessed the presence of flavonoid pathway intermediates in C. globosum extracts using LC-MS/MS. The presence of several key metabolites, such as dihydrokaempferol, chalcone, galangin, baicalein, chrysin, p-Coumaroyl-CoA, and p-Cinnamoyl-CoA, indicates the role of flavonoid biosynthesis machinery in the marine fungus. Further, we have aimed to enhance the production of chrysin with three different strategies: (1) optimizing the fermentation parameters, namely, growth medium, incubation time, pH, and temperature; (2) feeding key flavonoid pathway intermediates, i.e., phenylalanine and cinnamic acid; (3) elicitation with biotic elicitors, such as polysaccharide, yeast extract, and abiotic elicitors that include UV radiation, salinity, and metal stress. The combined effect of the optimized parameters resulted in a 97-fold increase in the chrysin yield, resulting in a fungal cell factory. This work reports the first approach for enhanced production of chrysin and can serve as a template for flavonoid production enhancement using marine endophytic fungi.

Influence of gamma radiation and phenylalanine on secondary metabolites in callus cultures of milk thistle (Silybum marianum L.)

BACKGROUND

A useful technique for growing large amounts of plant material is in vitro propagation of important medicinal plants. The present investigation deals with the enhancement of secondary metabolite production via elicitation using gamma (γ)-radiation and phenylalanine (Phe) precursor feeding in callus cultures of Silybum marianum L.

RESULTS

Seeds were exposed to two doses of γ-radiation (25 and 50 Gy) and the calli derived from stem explants  obtained from seedlings of these radiated seeds were treated with different concentrations of Phe. The biosynthesis of phenols and flavonoids was evaluated. It was found that callus cultures derived from explants of the seeds exposed to 25 Gy γ-radiation and treated with 4 mg/l Phe accumulated the maximum phenolic content (34.27±0.02 mg/g d.wt.), while the highest flavonoid content (9.56±0.12 mg/g d.wt.) was found in callus cultures derived from explants of seeds radiated with 25 Gy γ-radiation and subjected to 1 mg/l Phe. Similarly, HPLC quantification revealed that the production of flavonoids was highly accumulated (1343.06 μg/mg d.wt.) in callus cultures from explants of seeds  exposed to 25 Gy γ-radiation and grown at 1 mg/l Phe compared to the other treatments. In addition, a total of 11 important flavonoids have been determined in all callus cultures, except for acacetin-7-O-rutinoside, which was not found in the callus culture of the control.

CONCLUSIONS

These findings suggest that γ-radiation combined with Phe can improve the metabolism of S. marianum L. and could be used to produce such valuable metabolites on a commercial scale.

Stimulation of Lignan Production in Schisandra rubriflora In Vitro Cultures by Elicitation

The study investigated the effect of elicitation with: chitosan (CH) (200 mg/L), yeast extract (YeE) (3000 mg/L), ethephon (ETH) (25 µM/L), and methyl jasmonate (MeJA) (50 µM/L), on lignan accumulation in agitated and bioreactor (Plantform temporary immersion systems) microshoot cultures of female (F) and male (M) Schisandra rubriflora Rehd. et Wils. (Schisandraceae) lines. The elicitors were supplemented on the 10th day of culture. Biomasses were collected at 24 h and 48 h, and 4, 6, and 8 days after the addition of each elicitor. The 24 compounds from the dibenzocyclooctadiene, aryltetralin, dibenzylbutane, and tetrahydrofuran lignans and neolignans were determined qualitatively and quantitatively in biomass extracts using the UHPLC–MS/MS method. The highest total contents [mg/100 g DW] of lignans were: for CH-95.00 (F, day 6) and 323.30 (M, 48 h); for YeE 104.30 (F, day 8) and 353.17 (M, day 4); for ETH 124.50 (F, 48 h) and 334.90 (M, day 4); and for MeJA 89.70 (F, 48 h) and 368.50 (M, 24 h). In the biomass extracts of M cultures grown in bioreactors, the highest total lignan content was obtained after MeJA elicitation (153.20 mg/100 g DW). The maximum total lignan contents in the biomass extracts from agitated and bioreactor cultures were 3.29 and 1.13 times higher, respectively, than in the extracts from the non-elicited cultures. The poor understanding of the chemical composition and the lack of studies in the field of plant biotechnology of S. rubriflora emphasize the innovativeness of the research.

Effect of explant type (leaf, stem) and 2,4-D concentration on callus induction: influence of elicitor type (biotic, abiotic), elicitor concentration and elicitation time on biomass growth rate and costunolide biosynthesis in gazania (Gazania rigens) cell suspension cultures

Gazania rigens (L.) Gaertn. (Asteraceae) is a medicinal plant with high ornamental potential and use in landscaping. The therapeutic potential of sesquiterpene lactones (SLs) as plant natural products for pharmaceutical development has gained extensive interest with costunolide (chemical name: 6E,10E,11aR-6,10-dimethyl-3-methylidene-3a,4,5,8,9,11a-hexahydrocyclodeca[b]furan-2-one) used as a popular herbal remedy due to its anti-cancer, antioxidant, anti-inflammatory, anti-microbial, anti-allergic, and anti-diabetic activities, among others. In the present study, two explant types (leaf, stem) and four 2,4-dichlorophenoxy acetic acid (2,4-D) concentrations (0, 0.5, 1 and 2 mg/L) were tested for callusing potential. The results showed that stem explants treated with 1.5 mg/L 2,4-D exhibited higher callus induction percentage (90%) followed by leaf explants (80%) with 1 mg/L 2,4-D, after a 4-week period. Cell suspension cultures were established from friable callus obtained from stem explants following a sigmoid pattern of growth curve with a maximum fresh weight at 20 days of subculture and a minimum one at 5 days of subculture. In the following stage, the effects of elicitation of cell suspension cultures with either yeast extract (YE) or methyl jasmonate (MeJA), each applied in five concentrations (0, 100, 150, 200 and 250 mg/L) on cell growth (fresh and dry biomass) and costunolide accumulation were tested. After 20 days of culture, YE or MeJA suppressed cell growth as compared to the non-elicited cells, while costunolide accumulation was better enhanced under the effect of 150 mg/L MeJA followed by 200 mg/L YE, respectively. In the subsequent experiment conducted, the optimal concentration of the two elicitors (200 mg/L YE, 150 mg/L MeJA) was selected to investigate further elicitation time (0, 5, 10, 15 and 20 days). The results revealed that YE biotic elicitation stimulated cell growth and costunolide production, being maximum on day 20 for fresh biomass, on day 5 for dry biomass and on day 15 for the bioactive compound. Accordingly, cell growth parameters were maximized under the effect of abiotic elicitation with MeJA for 15 days, while highest costunolide content was achieved after 10 days. Overall, MeJA served as a better elicitor type than YE for biomass and costunolide production. Irrespective of elicitor type, elicitor concentration and elicitation time, maximal response was obtained with 150 mg/L MeJA for 10 days regarding costunolide accumulation (18.47 ppm) and 15 days for cell growth (fresh weight: 954 mg and dry weight: 76.3 mg). The application of elicitors can lead the large quantity of costunolide to encounter extensive range demand through marketable production without endangering of G. rigens.

Elicitor mediated enhancement of shoot biomass and lupeol production in Hemidesmus indicus (L.) R. Br. ex. Schult. and Tylophora indica (Burm. F.) Merrill using yeast extract and salicylic acid

Hemidesmus indicus (L.) R. Br. ex Schult. and Tylophora indica (Burm. F.) Merrill shoot cultures were treated with different concentrations of yeast extract (YE; 25-200 mg/L) and salicylic acid (SA; 50-200 µM), and their effect on lupeol production was assessed. The maximum dry weight (DW) biomass was recorded when H. indicus shoots were treated with SA (50 µM) and T. indica shoots with YE (200 mg/L). Highest lupeol yield (335.40 ± 0.04 µg/g DW) was obtained in H. indicus shoots after treatment with 50 µM of SA for 3 weeks. Whereas in T. indica, maximum lupeol content (584.26 ± 8.14 µg/g DW) was recorded by giving treatment with 25 μM of SA for 6 weeks.

Using the Strategy of Inducing and Genetically Transforming Plant Suspension Cells to Produce High Value-Added Bioactive Substances

Plants can produce many functional bioactive substances. The suspension cell system of plants can be constructed based on its characteristics to realize the large-scale production of valuable products. In this review, we mainly talk about the main strategies, elicitation, and genetic transformation to improve the yield of active substances by using this system. Meanwhile, we focus on the challenges hiding in the practical application and the future prospects and provide new ideas and the theoretical basis for obtaining numerous bioactive substances from plants.

Interactive effects of zinc oxide nano particles and different light regimes on growth and silymarin biosynthesis in callus cultures of Silybum marianum L

Silybum marianum L. commonly known as milk thistle is a medicinally potent plant with a multitude of pharmacological applications. The present investigations demonstrated the effects of Zinc Oxide nanoparticles (ZnO NPs) on callus growth and biosynthesis of silymarin in milk thistle under various light conditions. The callus cultures developed on Murashige and Skoog (MS) basal media containing ZnO NPs (0.15 mg/L), under the dark condition maintained for two weeks, followed by transference into normal light produced the maximum callus fresh weight (2294 mg/L FW). Further, the metabolite profiling revealed that ZnO NPs significantly augmented the production of silymarin and upregulated the antioxidant system in the callus cultures. Maximum TPC (total phenolic content: 37 ± 0.20 mg/g DW), TFC (total flavonoid content: 8.9 ± 0.023), DPPH antioxidant activity (91.5 ± 1.75%), Superoxide dismutase activity (SOD: 4.1 ± 0.045 nM/min/mg FW) and the highest silymarin content (14.6 ± 0.023 mg/g DW) were recorded in the callus cultures developed on MS media supplemented with solitary ZnO NPs (0.15 mg/L). While the callus culture evolved in presence of only PGRs (2,4 D and BA: 2 mg/L, each) accumulated the lesser fresh weight (562 mg/L FW). A higher concentration of ZnO NPs (0.15 mg/L) enhanced the secondary metabolite accumulation and silymarin content in the callus of Silybum marianum. This is the first standardized protocol to be applied on the industrial level for the production of silymarin.

Plant growth promoters mediated quality and yield attributes of milk thistle (Silybum marianum L.) ecotypes under salinity stress

Silybum marianum (L.) Gaertn (Astraceae) is a well-reputed medicinal plant mostly utilized for silymarin (Sily) content and oil production, however, the information about Sily contents in achene part is still fragmented under different climatic conditions. In this study four milk thistle ecotypes from Faisalabad (FSD), Gujranwala (GUJ), Quetta (QTA), and Kallar kahar (KK) having an altered achene color were analyzed under salt stress. Application of plant growth promoters (PGPs) is one of the solution for ameliorating the effect of salinity and increasing the quantity and quality traits of milk thistle, so ascorbic acid (AsA), thiourea (TU), and moringa leaf extract (MLE) were soil supplied after developing salinity stress (120 mM with irrigation) at germination stage. Predetermined levels were selected for PGPs such as AsA (500 µM), MLE (3%), and TU (250 µM). Results revealed that all yield related attributes were significantly decreased, while secondary metabolites, pericarp epidermis, pericarp parenchyma, and pericarp seed integument increased under salinity stress. Data suggested that PGPs treatment was helpful to alleviate the deleterious effects of salinity stress and enhance the milk thistle quality and quantity parameters. The ecotypic variations with altered achene color patterns represent an advantage for QTA ecotypes for higher Sily extraction under salt stressed conditions.

Biotechnological processes to obtain bioactive secondary metabolites from some Mexican medicinal plants

The consumption of medicinal plants has increased in recent decades due to the fact that they biosynthesize compounds with many biological activities; thus, some plant species with biological potential are being utilized as raw material by the industries for preparation of drugs, phytodrugs, or food supplements. This has the consequence of overexploitation and deforestation, which endangers plant species-of-interest. In recent years, alternatives have been sought to eradicate this problem. A solution that was given and is maintained is plant biotechnology, which favors the production of secondary metabolites (SMt) with important biological activity. Plant biotechnology allows us to increase the yield of a compound-of-interest, reduces its production times and costs, and allows constant and controlled production of the raw material, while aiding in the protection of medicinal plants that are found in danger of extinction. In the scientific literature, procuring the SMt by means of biotechnological processes is described, highlighting the study of five species from Mexican traditional medicine (Lopezia racemosa, Galphimia glauca, Cnidoscolus chayamansa, and Buddleja cordata), and the main biological activities are as follows: anti-inflammatory, hepatoprotector, neuroprotector, anxiolytic, antitumoral, antibacterial, and antioxidant, among others. KEY POINTS: • Secondary metabolites produce by biotechnology processes • Active secondary metabolites isolated from Mexican medicinal plants • Recent advances on the production of some bioactive secondary metabolites.

Effect of gamma rays and colchicine on silymarin production in cell suspension cultures of Silybum marianum: A transcriptomic study of key genes involved in the biosynthetic pathway

The aim of this study was to investigate secondary metabolite production in Silybum marianum L. cell suspension cultures obtained from seeds treated with gamma rays (200 and 600 Gy) and 0.05% colchicine. The effects of these treatments on callus induction, growth, viability, and silymarin production were studied, along with the changes in the transcriptome and DNA sequence of chalcone synthase (CHS) genes. The effect of gamma radiation (200 and 600 Gy) on silymarin production in S. marianum dry seeds was also studied using HPLC-UV. All three treatments induced high callus biomass production from leaf segments. The viability of the cell suspension cultures was over 90%. The flavonolignan content measured in the extracellular culture medium of the S. marianum cell suspension was highest after treatment with 600 Gy, followed by 0.05% colchicine, and finally, 200 Gy, after a growth period of 12 days. In general, an increased expression of CHS1, CHS2, and CHS3 genes, accompanied by an increase of silymarin content, was observed in response to all the studied treatments, although the effect was greatest on CHS2 expression. Bioinformatics analysis confirmed that the three CHS2 clones exhibited the highest genetic variation, both in relation to each other and to the CHS1 and CHS3 clones. Based on the results, S. marianum plants obtained from seeds previously exposed to 600 and 200 Gy as well as colchicine constitute a renewable resource with the potential to obtain large amounts of silymarin.

Bioproduction process of natural products and biopharmaceuticals: Biotechnological aspects

Decades of research have been put in place for developing sustainable routes of bioproduction of high commercial value natural products (NPs) on the global market. In the last few years alone, we have witnessed significant advances in the biotechnological production of NPs. The development of new methodologies has resulted in a better understanding of the metabolic flux within the organisms, which have driven manipulations to improve production of the target product. This was further realised due to the recent advances in the omics technologies such as genomics, transcriptomics, proteomics, metabolomics and secretomics, as well as systems and synthetic biology. Additionally, the combined application of novel engineering strategies has made possible avenues for enhancing the yield of these products in an efficient and economical way. Invention of high-throughput technologies such as next generation sequencing (NGS) and toolkits for genome editing Clustered Regularly Interspaced Short Palindromic Repeats/CRISPR-associated 9 (CRISPR/Cas9) have been the game changers and provided unprecedented opportunities to generate rationally designed synthetic circuits which can produce complex molecules. This review covers recent advances in the engineering of various hosts for the production of bioactive NPs and biopharmaceuticals. It also highlights general approaches and strategies to improve their biosynthesis with higher yields in a perspective of plants and microbes (bacteria, yeast and filamentous fungi). Although there are numerous reviews covering this topic on a selected species at a time, our approach herein is to give a comprehensive understanding about state-of-art technologies in different platforms of organisms.

Chitosan Elicitation Impacts Flavonolignan Biosynthesis in Silybum marianum (L.) Gaertn Cell Suspension and Enhances Antioxidant and Anti-Inflammatory Activities of Cell Extracts

Silybum marianum (L.) Gaertn is a rich source of antioxidants and anti-inflammatory flavonolignans with great potential for use in pharmaceutical and cosmetic products. Its biotechnological production using in vitro culture system has been proposed. Chitosan is a well-known elicitor that strongly affects both secondary metabolites and biomass production by plants. The effect of chitosan on S. marianum cell suspension is not known yet. In the present study, suspension cultures of S. marianum were exploited for their in vitro potential to produce bioactive flavonolignans in the presence of chitosan. Established cell suspension cultures were maintained on the same hormonal media supplemented with 0.5 mg/L BAP (6-benzylaminopurine) and 1.0 mg/L NAA (α-naphthalene acetic acid) under photoperiod 16/8 h (light/dark) and exposed to various treatments of chitosan (ranging from 0.5 to 50.0 mg/L). The highest biomass production was observed for cell suspension treated with 5.0 mg/L chitosan, resulting in 123.3 ± 1.7 g/L fresh weight (FW) and 17.7 ± 0.5 g/L dry weight (DW) productions. All chitosan treatments resulted in an overall increase in the accumulation of total flavonoids (5.0 ± 0.1 mg/g DW for 5.0 mg/L chitosan), total phenolic compounds (11.0 ± 0.2 mg/g DW for 0.5 mg/L chitosan) and silymarin (9.9 ± 0.5 mg/g DW for 0.5 mg/L chitosan). In particular, higher accumulation levels of silybin B (6.3 ± 0.2 mg/g DW), silybin A (1.2 ± 0.1 mg/g DW) and silydianin (1.0 ± 0.0 mg/g DW) were recorded for 0.5 mg/L chitosan. The corresponding extracts displayed enhanced antioxidant and anti-inflammatory capacities: in particular, high ABTS antioxidant activity (741.5 ± 4.4 μM Trolox C equivalent antioxidant capacity) was recorded in extracts obtained in presence of 0.5 mg/L of chitosan, whereas highest inhibitions of cyclooxygenase 2 (COX-2, 30.5 ± 1.3 %), secretory phospholipase A2 (sPLA2, 33.9 ± 1.3 %) and 15-lipoxygenase (15-LOX-2, 31.6 ± 1.2 %) enzymes involved in inflammation process were measured in extracts obtained in the presence of 5.0 mg/L of chitosan. Taken together, these results highlight the high potential of the chitosan elicitation in the S. marianum cell suspension for enhanced production of antioxidant and anti-inflammatory silymarin-rich extracts.

Enhanced Production of β-Caryophyllene by Farnesyl Diphosphate Precursor-Treated Callus and Hairy Root Cultures of Artemisia vulgaris L

Artemisia vulgaris L. produces a wide range of valuable secondary metabolites. The aim of the present study is to determine the effects of various concentrations of farnesyl diphosphate (FDP) on β-caryophyllene content in both callus and hairy root (HR) cultures regeneration from leaf explants of A. vulgaris L. Murashige and Skoog (MS) medium supplemented with various concentrations of 2,4-dichlorophenoxyacetic acid (2,4D; 4-13 μM), α-naphthaleneacetic acid (NAA; 5-16 μM), and FDP (1 and 3 μM) was used for callus induction and HR regeneration from leaf explants of A. vulgaris L. In this study, precursor-treated (2,4D 13.5 μM + FDP 3 μM) callus displayed the highest biomass fresh weight (FW)/dry weight (DW): 46/25 g, followed by NAA 10.7 μM + FDP 3 μM with FW/DW: 50/28 g. Two different Agrobacterium rhizogenes strains (A₄ and R₁₀₀₀) were evaluated for HR induction. The biomass of HRs induced using half-strength MS + B₅ vitamins with 3 μM FDP was FW/DW: 40/20 g and FW/DW: 41/19 g, respectively. To determine β-caryophyllene accumulation, we have isolated the essential oil from FDP-treated calli and HRs and quantified β-caryophyllene using gas chromatography-mass spectrometry (GC-MS). The highest production of β-caryophyllene was noticed in HR cultures induced using A₄ and R₁₀₀₀ strains on half-strength MS medium containing 3 μM FDP, which produced 2.92 and 2.80 mg/ml β-caryophyllene, respectively. The optimized protocol can be used commercially by scaling up the production of a β-caryophyllene compound in a short span of time.

Improvement of stilbene production by mulberry Morus alba root culture via precursor feeding and co-elicitation

Large amounts of Morus alba L. (MA) roots are needed as the source of active stilbenes in the industrial production of traditional medicines and cosmeceuticals. A recent investigation demonstrated resveratrol and its derivatives to be promising anti-COVID-19 agents. However, conventional cultivation of MA does not meet the demand for its stilbenes, and root quality usually varies between crops. This study established the in vitro non-GMO root culture of MA and optimized the root density, precursor feeding, and elicitors for stilbene productivity. A root culture with optimal inoculum density (3 g/flask of 30 mL medium) accumulated mulberroside A, oxyresveratrol, and resveratrol at 18.7 ± 1.00 mg/g, 136 ± 5.05 µg/g, and 41.6 ± 5.84 µg/g dry weight (DW), respectively. The feeding of L-tyrosine shortened the time required to reach the stilbene productive stage. Root cultures co-treated with 200 µM methyl jasmonate and 2 mg/mL yeast extract accumulated the highest contents of mulberroside A (30.3 ± 2.68 mg/g DW), oxyresveratrol (68.6 ± 3.53 µg/g DW), and resveratrol (10.2 ± 0.53 µg/g DW). In summary, root culture is a promising and sustainable source of stilbenes for the development of health products and agents for further investigation as potential anti-COVID-19 agents.

Enhanced Production of Bryonolic Acid in Trichosanthes cucumerina L. (Thai Cultivar) Cell Cultures by Elicitors and Their Biological Activities

Bryonolic acid is a triterpenoid compound found in cucurbitaceous roots. Due to its biological activities, this compound gets more attention to improve production. Herein, we carried out efficient ways with high bryonolic acid productions from Trichosanthes cucumerina L., a Thai medicinal plant utilizing plant cell cultures. The results showed that calli (24.65 ± 1.97 mg/g dry weight) and cell suspensions (15.69 ± 0.78 mg/g dry weight) exhibited the highest bryonolic acid productions compared with natural roots (approximately 2 mg/g dry weight). In the presence of three elicitors (methyl jasmonate, yeast extract, and chitosan), cell suspensions treated with 1 mg/mL of chitosan for eight days led to higher bryonolic acid contents (23.56 ± 1.68 mg/g dry weight). Interestingly, cell culture and root extracts with high bryonolic acid contents resulted in significantly higher percent cell viabilities than those observed under control (1% v/v DMSO) treatment in Saos-2 and MCF-7 cells. The present study indicated that T. cucumerina L. cell cultures are alternative and efficient to produce the biologically important secondary metabolite.

Methyl Jasmonate Induced Oxidative Stress and Accumulation of Secondary Metabolites in Plant Cell and Organ Cultures

Recently, plant secondary metabolites are considered as important sources of pharmaceuticals, food additives, flavours, cosmetics, and other industrial products. The accumulation of secondary metabolites in plant cell and organ cultures often occurs when cultures are subjected to varied kinds of stresses including elicitors or signal molecules. Application of exogenous jasmonic acid (JA) and methyl jasmonate (MJ) is responsible for the induction of reactive oxygen species (ROS) and subsequent defence mechanisms in cultured cells and organs. It is also responsible for the induction of signal transduction, the expression of many defence genes followed by the accumulation of secondary metabolites. In this review, the application of exogenous MJ elicitation strategies on the induction of defence mechanism and secondary metabolite accumulation in cell and organ cultures is introduced and discussed. The information presented here is useful for efficient large-scale production of plant secondary metabolites by the plant cell and organ cultures.

Ecotoxicity evaluation and human risk assessment of an agricultural polluted soil

The present study aims to evaluate the nature and level of chemical pollution as well as the potential toxicity and ecotoxicity of an agricultural soil irrigated by the water of Litani River. Our findings showed that the soil was mainly contaminated by alkanes (hentriacontane, octadecane, hexadecane) and metal trace elements (nickel, vanadium, chromium, and manganese). Soil organic extracts showed high cytotoxicity against human hepatic (HepG2) and bronchial epithelial cells (Beas-2B). Soil ecotoxicity was revealed by seed germination inhibition of several plant species (wheat, clover, alfalfa, tall fescue, and ryegrass) ranging from 7 to 30% on the polluted soil compared to non-polluted one. In addition, significant decreases in telluric microbial biomasses (bacterial and fungal biomasses), quantified by phospholipid fatty acids (PLFA) analysis were observed in polluted soil compared to non-contaminated soils. The density of the arbuscular mycorrhizal fungal (AMF) spores isolated from the polluted soil was about 316 spores/100 g. Three main AMF species were identified as Funelliformis mosseae, Septoglomus constrictum, and Claroideoglomus lamellosum. Moreover, 16 indigenous plant species were inventoried with Silybum marianum L. as the dominant one. Plant biodiversity indices (Shannon, Simpson, Menhinick, and Margaleff) were lower than those found in other contaminated soils. Finally, it was found that all the present plant species on this polluted site were mycorrhized, suggesting a possible protection of these plants against encountered pollutants, and the possibility to use AMF-assisted phytoremediation to clean-up such a site.

Functional study of CHS gene family members in citrus revealed a novel CHS gene affecting the production of flavonoids

BACKGROUND

Citrus flavonoids are considered as the important secondary metabolites because of their biological and pharmacological activities. Chalcone synthase (CHS) is a key enzyme that catalyses the first committed step in the flavonoid biosynthetic pathway. CHS genes have been isolated and characterized in many plants. Previous studies indicated that CHS is a gene superfamily. In citrus, the number of CHS members and their contribution to the production of flavonoids remains a mystery. In our previous study, the copies of CitCHS2 gene were found in different citrus species and the sequences are highly conserved, but the flavonoid content varied significantly among those species.

RESULTS

From seventy-seven CHS and CHS-like gene sequences, ten CHS members were selected as candidates according to the features of their sequences. Among these candidates, expression was detected from only three genes. A predicted CHS sequence was identified as a novel CHS gene. The structure analysis showed that the gene structure of this novel CHS is very similar to other CHS genes. All three CHS genes were highly conserved and had a basic structure that included one intron and two exons, although they had different expression patterns in different tissues and developmental stages. These genes also presented different sensitivities to methyl jasmonate (MeJA) treatment. In transgenic plants, the expression of CHS genes was significantly correlated with the production of flavonoids. The three CHS genes contributed differently to the production of flavonoids.

CONCLUSION

Our study indicated that CitCHS is a gene superfamily including at least three functional members. The expression levels of the CHS genes are highly correlated to the biosynthesis of flavonoids. The CHS enzyme is dynamically produced from several CHS genes, and the production of total flavonoids is regulated by the overall expression of CHS family genes.

Biochemical characterization of a key step involved in 2H4MB production in Decalepis hamiltonii

Decalepis hamiltonii is widely known for its flavour molecule 2-Hydroxy-4-Methoxy Benzaldehyde (2H4MB), a structural isomer of vanillin. As the biosynthetic pathway of 2H4MB is not known, we hypothesised 2H4MB origins could be from phenylpropanoid pathway (PPP). Accordingly, a study was conducted using PPP inhibitors (viz. piperonylic acid, MDCA and propanil) against in vitro root cultures of D. hamiltonii to find the branch of PPP which catalyses the 2H4MB formation. HPLC analysis was carried out to quantify 2H4MB levels in control and respective inhibitor treated root cultures in vitro. The results obtained revealed that piperonylic acid did not inhibit 2H4MB biosynthesis in the given period, whereas MDCA and propanil had the marked inhibitory effect. The inhibitory effect was evident with 13.2, 33.6 and 37.9% decrease in 2H4MB levels at 50, 100 and 150mM concentration of MDCA respectively in comparison with control roots. Similarly, the inhibitory effect of propanil on 2H4MB biosynthesis was obvious with 23.7, 49.5 and 57.9% decrease in 2H4MB levels at 50, 100 and 150μM concentration of inhibitor respectively when compared with control roots. Propanil showed a greater slow down effect on 2H4MB biosynthesis compared to MDCA. Incorporation of 0.1, 0.5 and 1.0mM ferulic acid as a precursor to in vitro root cultures of D. hamiltonii showed an increase in 2H4MB levels at the rate of 3.1, 107 and 94.1% respectively as quantified by HPLC analysis. However, ferulic acid in conjunction with propanil did not show any increase in 2H4MB levels. This clearly explains that ferulic acid is channelled through the 4-CL (4-coumarate CoA ligase) enzyme, where it would be converted to feruloyl-CoA and could be further converted to 2H4MB in D. hamiltonii.

Cloning and expression analysis of chalcone synthase gene from Coleus forskohlii

Flavonoids are an important class of secondary metabolites that play various roles in plants such as mediating defense, floral pigmentation and plant-microbe interaction. Flavonoids are also known to possess antioxidant and antimicrobial activities. Coleus forskohlii (Willd.) Briq. (Lamiaceae) is an important medicinal herb with a diverse metabolic profile, including production of a flavonoid, genkwanin. However, components of the flavonoid pathway have not yet been studied in this plant. Chalcone synthase (CHS) catalyses the first committed step of flavonoid biosynthetic pathway. Full-length cDNA, showing homology with plant CHS gene was isolated from leaves of C. forskohlii and named CfCHS (GenBank accession no. KF643243). Theoretical translation of CfCHS nucleotide sequence shows that it encodes a protein of 391 amino acids with a molecular weight of 42.75 kDa and pI 6.57. Expression analysis of CfCHS in different tissues and elicitor treatments showed that methyl jasmonate (MeJA) strongly induced its expression. Total flavonoids content and antioxidant activity of C. forskohlii also got enhanced in response to MeJA, which correlated with increased CfCHS expression. Induction of CfCHS by MeJA suggest its involvement in production of flavonoids, providing protection from microbes during herbivory or mechanical wounding. Further, our in silico predictions and experimental data suggested that CfCHS may be posttranscriptionally regulated by miR34.

Silybum marianum cell cultures stably transformed with Vitis vinifera stilbene synthase accumulate t-resveratrol in the extracellular medium after elicitation with methyl jasmonate or methylated β-cyclodextrins

The growing demand for t-resveratrol for industrial uses has generated considerable interest in its production. Heterologous resveratrol production in plant cell suspensions, apart from requiring the introduction of only one or two genes, has the advantage of high biomass yield and a short cultivation time, and thus could be an option for large-scale production. Silybum marianum is the source of the flavonolignan silymarin. Phenylpropanoid synthesis in cultures of this species can be activated by elicitation with methyl jasmonate and methylated β-cyclodextrins, with products of the pathway (coniferyl alcohol and some isomers of the silymarin complex) being released into the medium. Given that stilbene synthase shares the same key precursors involved in flavonoid and /or monolignol biosynthesis, we explored the potential of metabolically engineered S. marianum cultures for t-resveratrol production. Cell suspensions were stably transformed with Vitis vinifera stilbene synthase 3 and the expression of the transgene led to extracellular t-resveratrol accumulation at the level of milligrams per litre under elicitation. Resveratrol synthesis occurred at the expense of coniferyl alcohol. Production of silymarin was less affected in the transgenic cultures, since the flavonoid pathway is limiting for its synthesis, due to the preferred supply of precursors for the monolignol branch. The fact that the expressed STS gene took excessively produced precursors of non-bioactive compounds (coniferyl alcohol), while keeping the metabolic flow for target secondary compounds (i.e. silymarin) unaltered, opens a way to extend the applications of plant cell cultures for the simultaneous production of both constitutive and foreign valuable metabolites.

Enhancement of silymarin and phenolic compound accumulation in tissue culture of Milk thistle using elicitor feeding and hairy root cultures

In the present study, the effects of the metabolite elicitors chitosan, methyl jasmonate (MeJA) and salicylic acid (SA) as well as the hairy root transformation were tested for silymarin and phenolic compound accumulation in in vitro cultures of Milk thistle. For callus induction, leaf explants were cultured on MS medium supplemented with 5 mg/l NAA + 2 mg/l Kin + 0.1 mg/l GA3. Chitosan, SA and MeJA were added separately in three concentrations 200, 400 and 800 mg/l; 10, 20 and 40 mg/l; 20, 40 and 80 mg/l, respectively, to hormone free B5 medium. Alternatively, cotyledons of 12 day old seedlings were transformed with Agrobacterium rhizogenes A4 strain. Overall, increasing the concentrations of the three elicitors dramatically increased the total silymarin content. Remarkably, the elicitors mainly enhanced the accumulation of silybine A&B that were not detected in un-treated callus culture (control). In addition, the hairy root culture triggered the accumulation of silybine A&B, and silydianin, which was not detected in the non-transgenic roots. The hairy root culture was superior in production of the phenolic compounds in comparison to the control and elicitor treatments. The hairy root cultures showed also higher antioxidant capacities than non-transformed cultures and/or chemically elicited-callus cultures. Thus hairy root provide instrumental in enhancing the production of economically valuable metabolite.

Silybin content and overexpression of chalcone synthase genes in Silybum marianum L. plants under abiotic elicitation

Silymarin, a Silybum marianum seed extract containing a mixture of flavonolignans including silybin, is being used as an antihepatotoxic therapy for liver diseases. In this study, the enhancing effect of gamma irradiation on plant growth parameters of S. marianum under salt stress was investigated. The effect of gamma irradiation, either as a single elicitor or coupled with salinity, on chalcone synthase (CHS) gene expression and silybin A + B yield was also evaluated. The silybin A + B content in S. marianum fruits was estimated by liquid chromatography-mass spectrometry (LC-MS/MS). An increase in silybin content was accompanied by up-regulation of the CHS1, CHS2 and CHS3 genes, which are involved in the silybin biosynthetic pathway. The highest silybin A + B production (0.77 g/100 g plant DW) and transcript levels of the three studied genes (100.2-, 91.9-, and 24.3-fold increase, respectively) were obtained with 100GY gamma irradiation and 4000 ppm salty water. The CHS2 and CHS3 genes were partially sequenced and submitted to the NCBI database under the accession numbers KT252908.1 and KT252909.1, respectively. Developing new approaches to stimulate silybin biosynthetic pathways could be a useful tool to potentiate the use of plants as renewable resources of medicinal compounds.

Variation in the flavonolignan composition of fruits from different Silybum marianum chemotypes and suspension cultures derived therefrom

Mature fruits collected from different milk thistle (Silybum marianum (L.) Gaertn.) plants, grown in various habitats in Europe, were analysed for silymarin content and variation in component composition. Two different German and Polish cultivars each, as well as fruits from Hungary and Bulgaria have been compared with respect to their ratio of flavonolignan regioisomers. Besides differences in total silymarin content (0.8%-4.9%), three distinct chemotypical variations in fruit flavonolignan regioisomer composition in the cultivars have been observed. Although the differences in the diastereomer ratios of silybin A/B and isosilybin A/B were not significant, they never appeared in a 1:1 ratio. In vitro cultures have been established from seedlings of three typical chemotypes for further insights into flavonolignan content and composition in suspension cultures and the release of these specialized compounds to the extracellular space. The differences in the three Silybum marianum chemotypes were also observed in the composition of the intracellular silymarin of suspension-cultured cells. Silymarin components released to the cell culture medium, however, showed a highly differing composition with only low amounts of silychristin and silydianin. Assays with crude protein extracts prepared from suspension cells or habituated medium of these three chemotypes did not result in differences in silymarin content or composition. In in vitro assays the formation of the regioisomers silydianin and silychristin were strongly influenced by the taxifolin:coniferyl alcohol concentration ratio.

Gene expression and flavonolignan production in fruits and cell cultures of Silybum marianum

The hepatoprotectant flavonolignan silymarin (Sm) is synthesized through 4-coumaroyl-CoA, which enters both the flavonoid and the monolignol pathway giving the two immediate precursors taxifolin (Tx) and coniferyl alcohol (CA), respectively. Sm formation occurs via oxidative radicalization of Tx and CA and is accumulated at high levels at final stages of maturation of Silybum marianum fruits. By contrast, Sm production is severely reduced in cell cultures of this species, although suspensions are able to excrete Sm compounds into the medium upon elicitation with methyl jasmonate (MeJA) or cyclodextrins (CD). Knowledge of gene expression is important to understand Sm dynamics and to develop strategies aimed at increasing production by means of cell cultures but, to date, only one gene of the pathway (chalcone synthase, SmCHS) has been cloned. Therefore, to elucidate the relationship between expression of Sm pathway genes and production of these metabolites, four cDNA fragments of genes putatively involved in flavonolignan biosynthesis, chalcone isomerase, flavanone 3-hydroxylase, flavonol 3'-hydroxylase and cinnamyl alcohol dehydrogenase, were isolated from Sm producing S. marianum fruits and their expression, together with that of the SmCHS, were studied both in fruits at different maturation stages and in elicited cell suspensions. Combined results at both transcript expression and metabolite levels at three different stages of fruit maturation revealed that the formation of the flavonoid moiety precedes flavonolignan biosynthesis, being Sm accumulation associated to expression of the monolignol pathway. There was not detectable accumulation of transcripts in cell suspensions, however, elicitation with MeJA or CD notably induced expression of the studied fragments. These results indicate that the five genes expressed during maturation of S. marianum fruits may contribute to observed increases in flavonolignan accumulation upon treatment of cell cultures with elicitors.

Elicitation, an Effective Strategy for the Biotechnological Production of Bioactive High-Added Value Compounds in Plant Cell Factories

Plant in vitro cultures represent an attractive and cost-effective alternative to classical approaches to plant secondary metabolite (PSM) production (the “Plant Cell Factory” concept). Among other advantages, they constitute the only sustainable and eco-friendly system to obtain complex chemical structures biosynthesized by rare or endangered plant species that resist domestication. For successful results, the biotechnological production of PSM requires an optimized system, for which elicitation has proved one of the most effective strategies. In plant cell cultures, an elicitor can be defined as a compound introduced in small concentrations to a living system to promote the biosynthesis of the target metabolite. Traditionally, elicitors have been classified in two types, abiotic or biotic, according to their chemical nature and exogenous or endogenous origin, and notably include yeast extract, methyl jasmonate, salicylic acid, vanadyl sulphate and chitosan. In this review, we summarize the enhancing effects of elicitors on the production of high-added value plant compounds such as taxanes, ginsenosides, aryltetralin lignans and other types of polyphenols, focusing particularly on the use of a new generation of elicitors such as coronatine and cyclodextrins.

Tilting Plant Metabolism for Improved Metabolite Biosynthesis and Enhanced Human Benefit

The immense chemical diversity of plant-derived secondary metabolites coupled with their vast array of biological functions has seen this group of compounds attract considerable research interest across a range of research disciplines. Medicinal and aromatic plants, in particular, have been exploited for this biogenic pool of phytochemicals for products such as pharmaceuticals, fragrances, dyes, and insecticides, among others. With consumers showing increasing interests in these products, innovative biotechnological techniques are being developed and employed to alter plant secondary metabolism in efforts to improve on the quality and quantity of specific metabolites of interest. This review provides an overview of the biosynthesis for phytochemical compounds with medicinal and other related properties and their associated biological activities. It also provides an insight into how their biosynthesis/biosynthetic pathways have been modified/altered to enhance production.

Medicinal plant cell suspension cultures: pharmaceutical applications and high-yielding strategies for the desired secondary metabolites

The development of plant tissue (including organ and cell) cultures for the production of secondary metabolites has been underway for more than three decades. Plant cell cultures with the production of high-value secondary metabolites are promising potential alternative sources for the production of pharmaceutical agents of industrial importance. Medicinal plant cell suspension cultures (MPCSC), which are characterized with the feature of fermentation with plant cell totipotency, could be a promising alternative "chemical factory". However, low productivity becomes an inevitable obstacle limiting further commercialization of MPCSC and the application to large-scale production is still limited to a few processes. This review generalizes and analyzes the recent progress of this bioproduction platform for the provision of medicinal chemicals and outlines a range of trials taken or underway to increase product yields from MPCSC. The scale-up of MPCSC, which could lead to an unlimited supply of pharmaceuticals, including strategies to overcome and solution of the associated challenges, is discussed.

Yield improvement strategies for the production of secondary metabolites in plant tissue culture: silymarin from Silybum marianum tissue culture

Plant cell culture can be a potential source for the production of important secondary metabolites. This technology bears many advantages over conventional agricultural methods. The main problem to arrive at a cost-effective process is the low productivity. This is mainly due to lack of differentiation in the cultured cells. Many approaches have been used to maximise the yield of secondary metabolites produced by cultured plant cells. Among these approaches: choosing a plant with a high biosynthetic capacity, obtaining efficient cell line for growth and production of metabolite of interest, manipulating culture conditions, elicitation, metabolic engineering and organ culture. This article gives an overview of the various approaches used to maximise the production of pharmaceutically important secondary metabolites in plant cell cultures. Examples of using these different approaches are shown for the production of silymarin from Silybum marianum tissue culture.

Induction of extracellular defense-related proteins in suspension cultured-cells of Daucus carota elicited with cyclodextrins and methyl jasmonate

Suspension cultured-cells (SCC) of Daucus carota were used to evaluate the effect of methyl jasmonate and cyclodextrins, separately or in combination, on the induction of defense responses, particularly the accumulation of pathogenesis-related proteins. A comparative study of the extracellular proteome (secretome) between control and elicited carrot SCC pointed to the presence of amino acid sequences homologous to glycoproteins which have inhibitory activity against the cell-wall-degrading enzymes secreted by pathogens and/or are induced when carrot cells are exposed to a pathogen elicitor. Other amino acid sequences were homologous to Leucine-Rich Repeat domain-containing proteins, which play an essential role in defense against pathogens, as well as in the recognition of microorganisms, making them important players in the innate immunity of this plant. Also, some tryptic peptides were shown to be homologous to a thaumatin-like protein, showing high specificity to abiotic stress and to different reticuline oxidase-like proteins that displayed high levels of antifungal activity, suggesting that methyl jasmonate and cyclodextrins could play a role in mediating defense-related gene product expression in SCC of D. carota. Apart from these elicitor-inducible proteins, we observed the presence of PR-proteins in both control and elicited carrot SCC, suggesting that their expression is mainly constitutive. These PR-proteins are putative class IV chitinases, which also have inhibitory activity against pathogen growth and the class III peroxidases that participate in response to environmental stress (e.g. pathogen attack and oxidative), meaning that they are involved in defense responses triggered by both biotic and abiotic factors.

Transport of flavonolignans to the culture medium of elicited cell suspensions of Silybum marianum

Cell suspension cultures of Silybum marianum are able to excrete silymarin compounds into the medium upon elicitation with methyl jasmonate or cyclodextrins. Knowledge of transport mechanism is important to understand Sm metabolism and to develop strategies aimed at increasing production by means of cell cultures. For these reasons, a pharmacological approach was undertaken in this work in order to elucidate the possible mechanism involved in the release of this class of secondary metabolites into the extracellular medium of suspensions. Treatment with an ionophore or NH4Cl displayed little effect in elicited cultures, thus indicating that secondary transport, which uses electrochemical gradients, is not involved in the release. Several inhibitors of ABC transporters showed differential effects. Sodium ortho-vanadate, a typical suppressor of ATPase activity, was highly toxic to cultures even at very low concentrations. The common Ca-channel blocker verapamil did not influence extracellular secondary metabolite accumulation. Glybenclamide and probenecid, both effective inhibitors of ABCC-type ABC transporters, strongly reduced silymarin secretion. A partial cDNA, SmABC1, which showed similarity to ABCC-type ABC transporters, was isolated by RT-PCR from silymarin-producing cultures. SmABC1 expression was enhanced by methyljasmonate and cyclodextrins. Brefeldin A, a fungal metabolite which affects vesicular trafficking by preventing GTP/GDP exchange, inhibited release in a dose dependent manner. These results suggest that excretion of silymarin and their precursors is a transporter-dependent active transport and that yet another mechanism involving a vesicle trafficking system seems to participate in driving this class of secondary metabolites to the extracellular compartment.

Role of polyamines in regulating silymarin production in Silybum marianum (L.) Gaertn (Asteraceae) cell cultures under conditions of calcium deficiency

As part of our efforts to identify the possible role of polyamines (PAs) in silymarin (Sm) production, the effects of calcium deprivation on cell growth and on endogenous PAs levels and Sm production by milk thistle (Silybum marianum (L.) Gaertn) grown in cell cultures were examined. Young cultured cells of the H2 line of S. marianum were transferred to a medium without calcium and with ethylene glycol-bis-(β-aminoethyl) ether-N,N,N',N'-tetraacetic acid present to chelate any free calcium in order to analyze the effects of this medium on the levels of PAs and Sm produced by the cells. During the 17 days of exposure to this calcium-free medium most of the cell populations were in the G0/G1 phase (from day 7 to day 14 of culture) while PA levels underwent a progressive decline up to day 17, after which they were no longer detectable. We observed that putrescine (Put) accumulation was always lower than that observed under normal conditions. The lack of calcium in the MS medium advances the onset of the stationary phase, whose beginning is marked by an increase in the Put/spermidine (Spd) index, raising the production of Sm; the suspensions were productive for a longer time and hence produced more of the substance. Our results indicate that under stress conditions the production of Sm in young-cell suspensions of S. marianum is not associated with high levels of PAs in the medium--contrary to what one would expect--allowing us to conclude that growth inhibition appears to be the factor responsible for the maximum Sm accumulation while PAs are not directly involved in the Sm synthesis pathway by milk thistle grown in culture.

An integrated proteomic approach to decipher the effect of methyl jasmonate elicitation on the proteome of Silybum marianum L. hairy roots

Jasmonate and its methyl derivative, methyl jasmonate (MeJA), are naturally occurring compounds that mediate several plant physiological processes in response to pathogen attack, wounding, and ozone. Exogenous application of jasmonates triggers defense responses that resemble those initiated by pathogen infection and also modulates the production of certain secondary metabolites in a variety of plant species. In this study, we treated the hairy root cultures of Silybum marianum L. with 100 μM MeJA and then measured the content of Silymarin (SLM). We observed that the SLM content increased significantly after 48 h of MeJA treatment and remained constant for 120 h. However, MeJA treatment caused a significant growth reduction after 96 h incubation. The activity of lipoxygenase as a key enzyme in the jasmonate biosynthesis pathway and anti-oxidative enzymes; peroxidase and ascorbate peroxidase was also significantly increased after MeJA treatment. To elucidate the global effect of jasmonate on gene expression of S. marianum, we employed high resolution two-dimensional gel electrophoresis coupled with tandem mass spectrometry. Out of 670 reproducibly detected protein spots which were analyzed on each given gel, 32 spots were up- or down regulated upon MeJA treatment. Of them, ten proteins such as ER binding protein, glutamine synthetase, pathogenesis-related protein, caffeoyl CoA O-methyltransferase, and profilin-1 could be identified by mass spectrometry analysis. The possible implications of the identified proteins on physiological outcome of MeJA application in S. marianum hairy root culture will be discussed.

Proteome alterations monitored by DIGE analysis in Silybum marianum cell cultures elicited with methyl jasmonate and methyl B cyclodextrin

Elicitation with methyl jasmonate (MeJA) or/and cyclodextrin (CD) strongly induced silymarin (Sm) accumulation in suspensions of Silybum marianum, with most of Sm isomers being detected in the culture medium. This induction provides a model platform to characterize the regulation of flavonolignan accumulation and release in response to elicitors and, with this aim, changes in the S. marianum cell proteome were investigated. The DIGE technique was used to detect statistically significant changes in the cell's proteome. A total number of 1269 unique spots were detected, 67 of which were de-regulated upon elicitation. Nineteen spots were identified by nLC-MS/MS database search analysis. Identified proteins belong to a few categories, including metabolism, stress and defense responses and transport processes. The most abundant group was represented by pathogenesis-related (PR) proteins and heat shock proteins. Two proteins related to transport process were identified and both were upregulated by elicitation. One was identified as Ras-related protein Rab11C of the Rab family of small ATPase superfamily. A second protein was identified as an ABC transporter. Some of the identified proteins are discussed with respect to their putative role in the extracellular flavonolignan accumulation in S. marianum cultures.

BIOLOGICAL SIGNIFICANCE

Most approaches to increase secondary metabolite yields using plant cell cultures have been focused on the optimization of its biosynthesis. The study of other post biosynthetic events, like chemical or enzymatic modifications, transport, storage/secretion and catabolism/degradation are also biotechnologically relevant. Secretion is of particular interest since if cell cultures are to be used routinely for the commercial production, they must release the targeted metabolites into the extracellular medium. Elicitor-induced silymarin accumulation and release in S. marianum cell cultures provide a responsive model system to profile both alterations in proteins related to monolignol/flavonoid biosynthesis and to identify potential systems involved in secretion of secondary metabolites. The proteomic approach undertaken in this work has permitted identify some of the events occurring in elicited S. marianum cell cultures. One attainment of this study is that a vesicular transport mechanism could be involved in the release of this class of secondary metabolites to the extracellular compartment. This finding forms a baseline for future research on a non-sequenced medicinal plant S. marianum at molecular level.

Improved silymarin content in elicited multiple shoot cultures of Silybum marianum L

Silybum marianum L. extracts are being used as antihepatotoxic therapy for liver diseases. Silymarin is a polyphenolic flavonoid mixture isolated from milk thistle which is believed to be responsible for the plant's hepatoprotective action. Regeneration of Silybum marianum plants from shoot tip explants and assessment of their morphogenic potential, silymarin total concentration and its major constituents upon exposure to medium composition alteration and different elicitors' application was targeted. Different concentrations of NaCl, quercetin, gamma irradiation and dried fungal extracts were used to elicit silymarin production in the cultures. The chemical composition of silymarin and its total concentration was investigated through HPLC at all the experiment stages. Multiple shoots were recorded after 3 weeks of culture on MS medium containing various concentrations of BA and/or NAA. IAA was more effective than NAA and IBA in inducing robust roots in shoot cultures. The flowering plants recorded 20 % and 40 % of the total plants number in the multiplication and rooting stages respectively. The highest total silymarin concentration reached its peak with (10 Gy) gamma-irradiation to be 6.598 % dry weight in the in vitro regenerated shoot tip explants. The in vitro grown flowers showed 1.7 times more sylimarin productivity as compared to that of the wild grown congruent.

Enhancement of diosgenin production in Dioscorea zingiberensis cell cultures by oligosaccharides from its endophytic fungus Fusarium oxysporum Dzf17

The effects of the oligosaccharides from the endophytic fungus Fusarium oxysporum Dzf17 as elicitors on diosgenin production in cell suspension cultures of its host Dioscorea zingiberensis were investigated. Three oligosaccharides, DP4, DP7 and DP10, were purified from the oligosaccharide fractions DP2-5, DP5-8 and DP8-12, respectively, which were prepared from the water-extracted mycelial polysaccharide of the endophytic fungus F. oxysporum Dzf17. When the cell cultures were treated with fraction DP5-8 at 20 mg/L on day 26 and harvested on day 32, the maximum diosgenin yield (2.187 mg/L) was achieved, which was 5.65-fold of control (0.387 mg/L). When oligosaccharides DP4, DP7 and DP10 were individually added to 26-day-old D. zingiberensis cell cultures at concentrations of 2, 4, 6, 8 and 10 mg/L in medium, DP7 at 6 mg/L was found to significantly enhance diosgenin production, with a yield of 3.202 mg/L, which was 8.27-fold of control. When the cell cultures were treated with DP7 twice on days 24 and 26, and harvested on day 30, both diosgenin content and yield were significantly increased and reached the maximums of 1.159 mg/g dw and 4.843 mg/L, both of which were higher than those of single elicitation, and were 9.19- and 12.38-fold of control, respectively.