The configuration of methyl jasmonate affects paclitaxel and baccatin III production in Taxus cells

Accumulation of Polyphenols and Associated Gene Expression in Hairy Roots of Salvia viridis Exposed to Methyl Jasmonate

Methyl jasmonate (MJA), a signaling molecule in stress pathways, can be used to induce secondary metabolite synthesis in plants. The present study examines its effects on the growth of Salvia viridis hairy roots, and the accumulation of bioactive compounds, and correlates it with the expression of genes involved in the phenylpropanoid pathway. To our knowledge, this study represents the first exploration of elicitation in S. viridis culture and the first comprehensive analysis of MJA's influence on such a wide array of genes within the polyphenol metabolic pathway in the Salvia genus. Plants were treated with 50 and 100 µM MJA, and samples were collected at intervals of one, three, five, and seven days post-elicitation. HPLC analysis revealed that MJA stimulated the accumulation of all tested compounds, with a 30% increase (38.65 mg/g dry weight) in total polyphenol content (TPC) on day five. Quantitative real-time polymerase chain reaction (RT-PCR) analysis demonstrated a significant increase in the expression of the phenylpropanoid pathway genes-TAT (tyrosine aminotransferase), HPPR (4-hydroxyphenylpyruvate reductase), PAL (phenylalanine ammonia-lyase), C4H (cinnamic acid 4-hydroxylase), 4CL (4-coumarate-CoA ligase), and RAS (rosmarinic acid synthase)-following MJA treatment. For the majority of the genes, this increase was observed after the first day of treatment. Importantly, our present results confirm strong correlations of the analyzed gene expression with polyphenol biosynthesis. These findings support the notion that hairy roots provide a promising biotechnological framework for augmenting polyphenol production. Additionally, the combination of elicitor treatment and transgenic technology emerges as a viable strategy to enhance the biosynthesis of these valuable metabolites.

Hyper-production of taxol from Aspergillus fumigatus, an endophytic fungus isolated from Taxus sp. of the Northern Himalayan region

Taxol® (generic name Paclitaxel) is a chemotherapeutic drug, effective against head, neck, breast, lung, bladder, ovary, and cervix cancers. Rising demands in chemotherapy and limited supply of natural taxol have ultimately increased the cost of the drug. Semi synthesis using taxol precursors is not able to meet the global supply and has intensified the need to find alternative ways of taxol production. In the present study, 34 different endophytes were isolated from Taxus sp. collected from Shimla, Himachal Pradesh (India). Primary screening of taxol-producing fungi was carried out based on the presence of dbat gene, essential for the taxol biosynthetic pathway. A fungal isolate TPF-06 was screened to be a taxol-producing strain based on the PCR amplification results. It was characterized and identified as Aspergillus fumigatus by 18S rRNA (Accession No. KU-837249). Multiple sequence alignment (MSA) of nuclear ribosomal internal transcribed spacer (ITS) region and phylogenetic analysis confirmed that strain belonged to A. fumigatus clade (Accession No. MF-374798) and is endophytic in nature. Presence of taxol was detected and quantified by High-Performance Liquid Chromatography (HPLC) and characterized by using Thin Layer Chromatography (TLC), Ultraviolet (UV) spectroscopy, Mass spectrometry (MS), Fourier-Transform Infrared Spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR) spectroscopy. Microbial fermentation in the S7 medium yielded 1.60 g/L of taxol, which to the best of our knowledge is the highest taxol production from an endophytic fungus. Findings of the present study suggest that the A. fumigatus is an excellent alternate source for taxol supply, and it may become a highly potent strain on a commercial scale. The involvement of dbat gene in A. fumigatus KU-837249 strain further suggested a way of increasing taxol yield in fungi by medium engineering and recombinant DNA technology in the future.

Lasiolactols A and B Produced by the Grapevine Fungal Pathogen Lasiodiplodia mediterranea

A strain of Lasiodiplodia mediterranea, a fungus associated with grapevine decline in Sicily, produced several metabolites in liquid medium. Two new dimeric γ-lactols, lasiolactols A and B (1 and 2), were characterized as (2S*,3S*,4R*,5R*,2'S*,3'S*,4'R*,5'R*)- and (2R*,3S*,4R*,5R*,2'R*,3'S*,4'R*,5'R*)-(5-(4-hydroxymethyl-3,5-dimethyl-tetrahydro-furan-2-yloxy)-2,4-dimethyl-tetrahydro-furan-3-yl]-methanols by IR, 1D- and 2D-NMR, and HR-ESI-MS. Other four metabolites were identified as botryosphaeriodiplodin, (5R)-5-hydroxylasiodiplodin, (-)-(1R,2R)-jasmonic acid, and (-)-(3S,4R,5R)-4-hydroxymethyl-3,5-dimethyldihydro-2-furanone (3 - 6, resp.). The absolute configuration (R) at hydroxylated secondary C-atom C(7) was also established for compound 3. The compounds 1 - 3, 5, and 6, tested for their phytotoxic activities to grapevine cv. Inzolia leaves at different concentrations (0.125, 0.25, 0.5, and 1 mg/ml) were phytotoxic and compound 5 showed the highest toxicity. All metabolites did not show in vitro antifungal activity against four plant pathogens.

The Influence of Methyl Jasmonate and Salicylic Acid on Secondary Metabolite Production in Rehmannia Glutinosa Libosch. Hairy Root Culture

Rehmannia glutinosa hairy roots were used to evaluate the effect of methyl jasmonate (MeJa) and salicylic acid (SA) on increase of root biomass and production of iridoids (catalpol, harpagide) and phenylethanoids (verbascoside and isoverbascoside). The elicitors were added to 23-day-old culture separately at concentrations between 50 and 200 μM or in combinations at concentrations of 50 and 100 μM. Roots were harvested 72 h and 120 h after elicitation. The type of elicitor, its concentration and exposure time were found to strongly affect the content of each analyzed compound. A 72-hour treatment with 200 μM MeJa was the most effective in increase of verbascoside content (60.07 mg·DW−1 equivalent to 845.45 mg·L−1) and isoverbascoside (1.77 mg·DW−1 equivalent to 24.94 mg·L−1): these respective amounts were roughly 10- and 6.4-fold higher than the control values (unelicited roots). Exposure to 150 μM MeJa provided optimal harpagide content after 72 hours (0.136 mg·DW−1; 7.5-fold increase compared to the control), and catalpol content after 120 hours (up to 2.145 mg·DW−1). The combination of MeJa and SA also resulted in higher levels of secondary metabolites compared to the control culture, although these levels were lower than those observed for MeJa alone at the optimal concentration and exposure time. SA alone was less efficient in enhancing metabolite production than MeJa.

De Novo characterization of a Cephalotaxus hainanensis transcriptome and genes related to paclitaxel biosynthesis

Cephalotaxus hainanensis, an endangered plant, is known to contain several metabolites with anti-cancer activity. Despite its clinical impact, the alkaloid metabolism of this species has remained largely uncharacterized. The potential of Cephalotaxus for metabolic engineering of medically interesting compounds has, so far, not been exploited, due to the almost complete lack of molecular information. We have therefore performed a high throughput RNA-seq analysis and assembled the transcriptome de novo. Raw reads comprising 4.3 Gbp were assembled de novo into 39,416 unique sequences (unigenes) with a mean length of 1,089.8 bp and a total assembly size of 45.8 Mbp, which equals to more than 50 times the number of Cephalotaxaceae sequences currently deposited in the GenBank (as of August 2013). As proof of principle for medically interesting pathways, gene fragments related to paclitaxel biosynthesis were searched and detected. To verify their functionality, the metabolic product paclitaxel, and its precursor baccatin III, were identified in the leaves of C. hainanensis by HPLC, and shown to be induced by MeJA. This finding demonstrates exemplarily the potential of the annotated transcriptome as information resource for the biotechnological exploitation of plant secondary metabolism.

Lasiojasmonates A-C, three jasmonic acid esters produced by Lasiodiplodia sp., a grapevine pathogen

In this study, a strain (BL 101) of a species of Lasiodiplodia, not yet formally described, which was isolated from declining grapevine plants showing wedge-shaped cankers, was investigated for its ability to produce in vitro bioactive secondary metabolites. From culture filtrates of this strain three jasmonic acid esters, named lasiojasmonates A-C and 16-O-acetylbotryosphaerilactones A and C were isolated together with (1R,2R)-jasmonic acid, its methyl ester, botryosphaerilactone A, (3S,4R,5R)-4-hydroxymethyl-3,5-dimethyldihydro-2-furanone and (3R,4S)-botryodiplodin. The structures of lasiojasmonates A-C were established by spectroscopic methods as (1R*,2R*,3'S*,4'R*,5'R*)-4-hydroxymethyl-3,5-dimethyldihydro-2-furanone, (1R*,2R*,3'S*,4'R*,5'R*,10'R*,12'R*,13'R*,14'S*) and (1R*,2R*,3'S*,4'R*,5'R*,10'S*,12'R*,13'R*,14'S*)-4-(4-hydroxymethyl-3,5-dimethyltetrahydro-furan-2-yloxymethyl)-3,5-dimethyldihydro-2-furanones jasmonates (1, 4 and 5). The structures of 16-O-acetylbotryosphaerilactones A and C were determined by comparison of their spectral data with those of the corresponding acetyl derivatives obtained by acetylation of botryosphaerilactone A. The metabolites isolated, except 4 and 5, were tested at 1mg/mL on leaves of grapevine cv. Cannonau and cork oak using the leaf puncture assay. They were also tested on detached grapevine leaves at 0.5mg/mL and tomato cuttings at 0.1mg/mL. In all phytotoxic assays only jasmonic acid was found to be active. All metabolites were inactive in the zootoxic assay at 50 μg/mL.

Identification and expression analysis of methyl jasmonate responsive ESTs in paclitaxel producing Taxus cuspidata suspension culture cells

Background

Taxol® (paclitaxel) promotes microtubule assembly and stabilization and therefore is a potent chemotherapeutic agent against wide range of cancers. Methyl jasmonate (MJ) elicited Taxus cell cultures provide a sustainable option to meet the growing market demand for paclitaxel. Despite its increasing pharmaceutical importance, the molecular genetics of paclitaxel biosynthesis is not fully elucidated. This study focuses on identification of MJ responsive transcripts in cultured Taxus cells using PCR-based suppression subtractive hybridization (SSH) to identify genes involved in global pathway control.

Results

Six separate SSH cDNA libraries of paclitaxel-accumulating Taxus cuspidata P991 cell lines were constructed at three different post-elicitation time points (6h, 18h and 5 day) to identify genes that are either induced or suppressed in response to MJ. Sequencing of 576 differentially screened clones from the SSH libraries resulted in 331 unigenes. Functional annotation and Gene Ontology (GO) analysis of up-regulated EST libraries showed enrichment of several known paclitaxel biosynthetic genes and novel transcripts that may be involved in MJ-signaling, taxane transport, or taxane degradation. Macroarray analysis of these identified genes unravelled global regulatory expression of these transcripts. Semi-quantitative RT-PCR analysis of a set of 12 candidate genes further confirmed the MJ-induced gene expression in a high paclitaxel accumulating Taxus cuspidata P93AF cell line.

Conclusions

This study elucidates the global temporal expression kinetics of MJ responsive genes in Taxus suspension cell culture. Functional characterization of the novel genes identified in this study will further enhance the understanding of paclitaxel biosynthesis, taxane transport and degradation.

Perspectives and limits of engineering the isoprenoid metabolism in heterologous hosts

Terpenoids belong to the largest class of natural compounds and are produced in all living organisms. The isoprenoid skeleton is based on assembling of C5 building blocks, but the biosynthesis of a great variety of terpenoids ranging from monoterpenoids to polyterpenoids is not fully understood today. Terpenoids play a fundamental role in human nutrition, cosmetics, and medicine. In the past 10 years, many metabolic engineering efforts have been undertaken in plants but also in microorganisms to improve the production of various terpenoids like artemisinin and paclitaxel. Recently, inverse metabolic engineering and combinatorial biosynthesis as main strategies in synthetic biology have been applied to produce high-cost natural products like artemisinin and paclitaxel in heterologous microorganisms. This review describes the recent progresses made in metabolic engineering of the terpenoid pathway with particular focus on fundamental aspects of host selection, vector design, and system biotechnology.

Paclitaxel: a review of adverse toxicities and novel delivery strategies

Better known as Taxol (Bristol-Myers Squibb), paclitaxel is the first member of the taxane family to be used in cancer chemotherapy. The taxanes exert their cytotoxic effect by arresting mitosis through microtubule stabilization, resulting in cellular apoptosis. The use of paclitaxel as a chemotherapeutic agent has become a broadly accepted option in the treatment of patients with ovarian, breast and non-small cell lung cancers, malignant brain tumors, and a variety of other solid tumors. However, significant toxicities, such as myelosuppression and peripheral neuropathy, limit the effectiveness of paclitaxel-based treatment regimens. This review addresses the toxicities associated with paclitaxel treatment and describes existing and future strategies of paclitaxel administration directed at limiting these toxicities.

Novel, unnatural benzo-1,2,3-thiadiazole-7-carboxylate elicitors of taxoid biosynthesis

In order to establish the chemical biological technology for production of valuable secondary metabolites, a novel family of unnatural elicitors derived from the plant activator benzo-1,2,3-thiadiazole-7-carboxylic acid were designed and synthesized. New synthetic elicitors that showed powerful eliciting activities upon taxoid biosynthesis by Taxus chinensis suspension cells were obtained. For example, benzo-1,2,3-thiadiazole-7-carboxylic acid 2-(2-hydroxybenzoxyl)ethyl ester was more effective and resulted in nearly 40% increase in taxuyunnanine C content and production in comparison with methyl jasmonate, which was previously reported as the most powerful chemical elicitor for taxoid biosynthesis. The novel class of elicitors was found to induce plant defense responses, including promotion of H(2)O(2) levels originating from oxidative burst and activation of phenylalanine ammonia lyase. Interestingly the plant defense responses induced corresponded well to the superior stimulating activity in T. chinensis cell cultures. The work indicates that the newly synthesized benzothiadiazoles can act as a new family of elicitors for taxoid biosynthesis in plant cells.

Novel fluoro- and hydroxyl-containing jasmonate derivatives as highly efficient elicitors in suspension cultures of Taxus chinensis

To develop more effective abiotic elicitors for cell suspension cultures of T. chinensis to meet the needs for paclitaxel as anti-tumor drug, some fluoro- or hydroxyl-containing groups are introduced to the ester moiety of jasmonic acid by the esterification or acylation with bis(trichloromethyl) carbonate and corresponding alcohol. Some of them are found to be novel and effective elicitors, which can enhance the production of taxuyunnanine C (Tc) up to 60% more than that by methyl jasmonate (MJA) in T. chinensis cell cultures.

Effects of immobilization by entrapment in alginate and scale-up on paclitaxel and baccatin III production in cell suspension cultures ofTaxus baccata

Paclitaxel and baccatin III-producing cells of Taxus baccata were immobilized within Ca(2+)-alginate beads. Under established optimum conditions for the biosynthesis of both taxanes, the yields of paclitaxel and baccatin III in shake-flask cultures of free cells increased by factors of up to 3 and 2, respectively, in the corresponding cultures of immobilized cells. Although the scale-up from shake-flask to bioreactor culture usually results in reduced productivities when both free and immobilized cells were grown in the same optimum conditions in three different bioreactor types (Stirred, Airlift, and Wave) running for 24 days in a batch mode and with the system optimized in each case, there was a considerable increase in the yields of paclitaxel and baccatin III. Among the reactors, the Stirred bioreactor was the most efficient in promoting immobilized cell production of paclitaxel, giving a content of 43.43 mg.L(-1) at 16 days of culture, equivalent to a rate of 2.71 mg.L(-1).day(-1). To our knowledge, the paclitaxel productivity obtained in this study is one of the highest reported so far by academic laboratories for Taxus species cultures in bioreactors.

A novel synthetic fluoro-containing jasmonate derivative acts as a chemical inducing signal for plant secondary metabolism

A novel fluoro-containing jasmonate derivative was chemically synthesized and evaluated as a potential elicitor with respect to the induction of plant defense responses and the biosynthesis of plant secondary metabolites. A bioactive taxuyunnanine C (Tc)-producing cell line of Taxus chinensis was taken as a model plant cell system. The presence of novel synthesized pentafluoropropyl jasmonate (PFPJA) induced two early and important events in plant defense responses, including an oxidative burst and activation of L-phenylalanine ammonia lyase. In addition, PFPJA was found to significantly increase Tc accumulation, without any inhibition of cell growth. Moreover, Tc accumulation was increased more in the presence of PFPJA compared with methyl jasmonate (MJA) and previously reported trifluoroethyl jasmonate (TFEJA). For example, addition of 100 muM PFPJA on day 7 led to a high Tc content (38.2 +/- 0.3 mg/g) at day 21, while the Tc content was 29.3 +/- 0.3 mg/g and 34.9 +/- 0.9 mg/g with the addition of 100 microM MJA and TFEJA, respectively. Quantitative structure-activity analysis of fluoro-containing jasmonates suggests that the increase in the fluoro-groups introduced into the carboxyl side-chain of MJA resulted in a higher stimulatory activity for Tc biosynthesis, which corresponds well with the markedly increased lipophilicity after fluorine introduction. These results indicate that newly synthesized fluoro-containing PFPJA can act as a powerful chemical inducing signal for secondary metabolism in plant cell cultures.

Plant-plant signaling: application of trans- or cis-methyl jasmonate equivalent to sagebrush releases does not elicit direct defenses in native tobacco

Nicotiana attenuata plants growing in close proximity to damaged sagebrush (Artemisia tridentata ssp. tridentata) suffer less herbivory than plants near undamaged sagebrush. Sagebrush constitutively releases methyl jasmonate (MeJA), a compound that when applied directly to N. attenuata, elicits herbivore resistance and the direct defense traits [protease inhibitors (PIs), nicotine]. Damage increases the release of volatile MeJA, primarily in the cis epimer, suggesting that cis-MeJA may mediate this apparent interplant signaling. We characterized sagebrush's MeJA plume before and after damage in nature and in the laboratory, and compared the activity of trans- and cis-MeJA in inducing PIs, nicotine, and Manduca sexta resistance in N. attenuata. We used both lanolin applications and aqueous sprays that mimic natural exposures, and we determined the amount of volatilized MeJA required to elicit a nicotine response in open-grown plants. Wounding rapidly and transiently increased cis-MeJA emissions from damaged parts (but not systemically), and the released plume did not rapidly dissipate in nature. cis-MeJA was not consistently more active than trans-MeJA, and the order of exposure (trans- then cis-) did not influence activity. We conclude that volatile MeJA, either trans- or cis-, when applied at levels consistent with those released by sagebrush does not elicit direct defenses in N. attenuata.

Novel chemically synthesized hydroxyl-containing jasmonates as powerful inducing signals for plant secondary metabolism

Novel hydroxyl-containing jasmonate derivatives were chemically synthesized and evaluated by bioassay as potential elicitors for stimulating the biosynthesis of plant secondary metabolites. A suspension culture of Taxus chinensis, which produces a bioactive taxoid, taxuyunnanine C (Tc), was taken as a model plant cell system. Experiments on the timing of addition of jasmonates and dose response indicated that day 7 and 100 microM was the optimal elicitation time and concentration, respectively, for both cell growth and Tc accumulation. Tc accumulation was increased more in the presence of novel hydroxyl-containing jasmonates compared to that with methyljasmonate (MJA) addition. For example, addition of 100 microM 2,3-dihydroxypropyl jasmonate on day 7 led to a very high Tc content of 47.2 +/- 0.5 mg/g (at day 21), whereas the Tc content was 29.2 +/- 0.6 mg/g (on the same day) with addition of 100 microM MJA. Quantitative structure-activity analysis of various jasmonates suggests that the optimal lipophilicity and the number of hydroxyl groups may be two important factors affecting their elicitation activity. In addition, the jasmonate elicitors were found to induce plant defense responses, including oxidative burst and activation of L-phenylalanine ammonia lyase (PAL). Interestingly, a higher level of H(2)O(2) production and PAL activity was detected with elicitation by the synthesized jasmonates compared with that by MJA, which corresponded well to the superior stimulating activity in the former. This work indicates that the newly synthesized hydroxyl-containing jasmonates can act as powerful inducing signals for secondary metabolite biosynthesis in plant cell cultures.

Recent Developments in the Maytansinoid Antitumor Agents

Maytansine and its congeners have been isolated from higher plants, mosses and from an Actinomycete, Actinosynnema pretiosum. Many of these compounds are antitumor agents of extraordinary potency, yet phase II clinical trials with maytansine proved disappointing. The chemistry and biology of maytansinoids has been reviewed repeatedly in the late 1970s and early 1980s; the present review covers new developments in this field during the last two decades. These include the use of maytansinoids as "warheads" in tumor-specific antibodies, preliminary metabolism studies, investigations of their biosynthesis at the biochemical and genetic level, and ecological issues related to the occurrence of such typical microbial metabolites in higher plants.

Identification and quantification of methyl jasmonate in leaf volatiles of Arabidopsis thaliana using solid-phase microextraction in combination with gas chromatography and mass spectrometry

Static headspace sampling with solid-phase microextraction has been used in combination with GC-FID and GC-MS for the specific enrichment, identification and quantification of volatile methyl jasmonate secreted by wounded leaves of Arabidopsis thaliana. The microsample method of analysis was found to be precise, accurate, sensitive and rapid. The detection limit of the procedure is 1.5 ppb (approximately 1.3 ng) per injection, which is of adequate sensitivity to detect the natural baseline levels of methyl jasmonate (approximately 10-100 ng/g) present in plant tissues. The method can be applied to most plants, requires a minimum of sample material, and shows the additional advantage that it is suitable for automation and could thus be used for high-throughput screening.

Taxol biosynthetic genes

The function and properties of heterologously expressed full-length cDNA clones, isolated from a Taxus cDNA library and specific to Taxol biosynthesis, are summarized. Recombinant enzymes are described that catalyze early steps of the pathway, including taxadiene synthase, taxadien-5alpha-ol-O-acetyltransferase and taxadien-5alpha-yl acetate 10beta-hydroxylase, and that catalyze late steps, including 10-deacetylbaccatin III-10beta-O-acetyltransferase and taxane 2alpha-O-benzoyltransferase. The properties of Taxus geranylgeranyl diphosphate synthase are also described; although this synthase does not mediate a committed step of Taxol biosynthesis, it does provide the universal plastidial diterpenoid precursor, geranylgeranyl diphosphate, for initiating Taxol biosynthesis.