The genetic manipulation of medicinal and aromatic plants

Production of Plant Proteins and Peptides with Pharmacological Potential

The use of plant proteins or peptides in biotechnology is based on their identification as possessing bioactive potential in plants. This is usually the case for antimicrobial, fungicidal, or insecticidal components of the plant's defense system. They function in addition to a large number of specialized metabolites. Such proteins can be classified according to their sequence, length, and structure, and this has been tried to describe for a few examples here. Even though such proteins or peptides can be induced during plant-pathogen interaction, they are still present in rather small amounts that make the system not suitable for the production in large-scale systems. Therefore, a suitable type of host needs to be identified, such as cell cultures or adult plants. Bioinformatic predictions can also be used to add to the number of bioactive sequences. Some problems that can occur in production by the plant system itself will be discussed, such as choice of promoter for gene expression, posttranslational protein modifications, protein stability, secretion of proteins, or induction by elicitors. Finally, the plant needs to be set up by biotechnological or molecular methods for production, and the product needs to be enriched or purified. In some cases of small peptides, a direct chemical synthesis might be feasible. Altogether, the process needs to be considered marketable.

Cell type matters: competence for alkaloid metabolism differs in two seed-derived cell strains of Catharanthus roseus

Since the discovery of the anticancer drugs vinblastine and vincristine, Catharanthus roseus has been intensively studied for biosynthesis of several terpene indole alkaloids (TIAs). Due to their low abundance in plant tissues at a simultaneously high demand, modes of production alternative to conventional extraction are mandatory. Plant cell fermentation might become one of these alternatives, yet decades of research have shown limited success to certain product classes, leading to the question: how to preserve the intrinsic ability to produce TIAs (metabolic competence) in cell culture? We used the strategy to use the developmental potency of mature embryos to generate such strains. Two cell strains (C1and C4) from seed embryos of Catharanthus roseus were found to differ not only morphologically, but also in their metabolic competence. This differential competence became manifest not only under phytohormone elicitation, but also upon feeding with alkaloid pathway precursors. The more active strain C4 formed larger cell aggregates and was endowed with longer mitochondria. These cellular features were accompanied by higher alkaloid accumulation in response to methyl jasmonate (MeJA) elicitation. The levels of catharanthine could be increased significantly, while the concurrent vindoline branch of the pathway was blocked, such that no bisindole alkaloids were detectable. By feeding vindoline to MeJA-elicited C4 cells, vincristine became detectable; however, only to marginal amounts. In conclusion, these results show that cultured cells are not "de-differentiated", but can differ in metabolic competence. In addition to elicitation and precursor feeding, the cellular properties of the "biomatter" are highly relevant for the success of plant cell fermentation.

Plant-derived smoke water and karrikinolide (KAR1) enhance physiological activities, essential oil yield and bioactive constituents of Mentha arvensis L

Introduction

The current study was carried out with the hypothesis that foliar application of plant-derived smoke water (PDSW) and karrikinolide (KAR₁) might enhanced the plant growth, physiology, and essential oil production of the Mentha arvensis L. Karrikinolide (KAR₁) is one of the most important bioactive constituents of PDSW.

Methods

Mint (Mentha arvensis L.) was grown in natural conditions in the net-house. Different concentrations of PDSW (1:125, 1:250, 1:500 and 1:1000 v/v) and KAR₁ (10^-9 M, 10^-8 M, 10^-7 M and 10^-6 M) were used as foliar-spray treatments, using double-distilled water as control. The PDSW was prepared by burning the dried wheat-straw that acted as a growth-promoting substance.

Results

Foliar-spray treatment 1:500 v/v of PDSW and 10^-8 M of KAR₁ proved optimal for enhancing all morphological, physiological, and essential-oil yield related parameters. In comparison with the control, 1:500 v/v of PDSW and 10^-8 M of KAR₁ increased significantly (p ≤ 0.05) the height of mint plant (19.23% and 16.47%), fresh weight (19.30% and 17.44%), dry weight (35.36% and 24.75%), leaf area (18.22% and 17.46%), and leaf yield per plant (28.41% and 23.74%). In addition, these treatments also significantly increased the photosynthetic parameters, including chlorophyll fluorescence (12.10% and 11.41%), total chlorophyll content (25.70% and 20.77%), and total carotenoid content (29.77% and 27.18%). Likewise, 1:500 v/v of PDSW and 10^-8 M of KAR₁ significantly increased the essential-oil content (37.09% and 32.25%), essential oil productivity per plant (72.22% and 66.66%), menthol content (29.94% and 25.42%), menthyl acetate content (36.90% and 31.73%), and menthone content (44.38% and 37.75%). Furthermore, the TIC chromatogram of the GCMS analysis revealed the presence of 34 compounds, 12 of which showed major peak areas.

Discussion

Treatment 1: 500 v/v of PDSW proved better than the treatment 10^-8 M of KAR₁ with regard to most of the parameters studied. The outcome of the study can be used as a recommendation tool for agricultural and horticultural crops, since it costs much lesser than that of KAR₁. In fact, the foliar application of PDSW proved economical and played bioactive role at very low concentrations.

A Brief Review of Plant Cell Transfection, Gene Transcript Expression, and Genotypic Integration for Enhancing Compound Production

Plants possess a plethora of important secondary metabolites, which are unique sources of natural pigments, pharmaceutical compounds, food additives, natural pesticides, and other industrial components. The commercial significance of such metabolites/compounds has directed the research toward their production and exploration of methods for enhancement of production. Biotechnological tools are critical in selecting, integrating, multiplying, improving, and analyzing medicinal plants for secondary metabolite production. Out of many techniques that are being explored to enhance secondary metabolite production, "plant cell transfection" is the latest tool to achieve maximum output from the plant source. It is based upon the introduction of foreign DNA into the plant cell relying on physical treatment such as electroporation, cell squeezing, sonoporation, optical transfection nanoparticles, magnetofection, and chemical treatment or biological treatment that depends upon carrier. One of the promising tools that have been exploited is CRISPR-Cas9. Overall, the abovementioned tools focus on the stable transfection of desired gene transcripts. Since the integration and continuous expression of transfected gene of particular trait represents stable transfection of host cell genome, resulting from transfer of required trait to daughter cells ultimately leading to enhanced production of secondary metabolites of interest. This chapter will review a set of biotechnological tools that are candidates for achieving the enhanced bioactive compound production indicated here to be used for drug discovery.

Anthelmintic Agents from African Medicinal Plants: Review and Prospects

Soil-transmitted helminthiasis affects more than 1.5 billion people globally and largely remains a sanitary problem in Africa. These infections place a huge economic burden on poor countries and affect livestock production, causing substantial economic losses and poor animal health. The emergence of anthelmintic resistance, especially in livestock, and the potential for its widespread in humans create a need for the development of alternative therapies. Medicinal plants play a significant role in the management of parasitic diseases in humans and livestock, especially in Africa. This report reviews anthelmintic studies that have been conducted on medicinal plants growing in Africa and published within the past two decades. A search was made in various electronic databases, and only full articles in English were included in the review. Reports show that aqueous and hydroalcoholic extracts and polar fractions obtained from these crude extracts form the predominant (80%) form of the extracts studied. Medicinal plants, extracts, and compounds with different chemical groups have been studied for their anthelmintic potential. Polyphenols and terpenoids are the most reported groups. More than 64% of the studies employed in vitro assays against parasitic and nonparasitic nematode models. Egg hatch inhibition, larval migration inhibition, and paralysis are the common parameters assessed in vitro. About 72% of in vivo models involved small ruminants, 15% rodents, and 5% chicken. Egg and worm burden are the main factors assessed in vivo. There were no reports on interventions in humans cited within the period under consideration. Also, few reports have investigated the potential of combining plant extracts with common anthelmintic drugs. This review reveals the huge potential of African medicinal plants as sources of anthelmintic agents and the dire need for in-depth clinical studies of extracts, fractions, and compounds from African plants as anthelmintic agents in livestock, companion animals, and humans.

Switching cell fate by the actin-auxin oscillator in Taxus: cellular aspects of plant cell fermentation

Paclitaxel synthesis in Taxus cells correlates with a cell-fate switch that leads to vacuoles of a glossy appearance and vermiform mitochondria. This switch depends on actin and apoplastic respiratory burst. Plant cell fermentation, the production of valuable products in plant cell culture, has great potential as sustainable alternative to the exploitation of natural resources for compounds of pharmaceutical interest. However, the success of this approach has remained limited, because the cellular aspects of metabolic competence are mostly unknown. The production of the anti-cancer alkaloid Paclitaxel has been, so far, the most successful case for this approach. In the current work, we map cellular aspects of alkaloid synthesis in cells of Taxus chinensis using a combination of live-cell imaging, quantitative physiology, and metabolite analysis. We show evidence that metabolic potency correlates with a differentiation event giving rise to cells with large vacuoles with a tonoplast that is of a glossy appearance, agglomerations of lipophilic compounds, and multivesicular bodies that fuse with the plasma membrane. Cellular features of these glossy cells are bundled actin, more numerous peroxisomes, and vermiform mitochondria. The incidence of glossy cells can be increased by aluminium ions, and this increase is significantly reduced by the actin inhibitor Latrunculin B, and by diphenylene iodonium, a specific inhibitor of the NADPH oxidase Respiratory burst oxidase Homologue (RboH). It is also reduced by the artificial auxin Picloram. This cellular fingerprint matches the implications of a model, where the differentiation into the glossy cell type is regulated by the actin-auxin oscillator that in plant cells acts as dynamic switch between growth and defence.

Biologically synthesized CuO nanoparticles induce physiological, metabolic, and molecular changes in the hazel cell cultures

The utilization of plant extracts in nanoparticle (NP) synthesis has been suggested as a nature-friendly method and an efficient alternative to the conventional approaches such as physical and chemical methods. Taxol is a valuable medicinal compound, and hazelnut has been suggested as one of the sustainable resources for producing this metabolite. In the present research, copper oxide (CuO) nanoparticles (NPs) were biologically synthesized by utilizing hazelnut leaf extracts. FTIR, XRD, EDAX, DLS, and SEM analyses were used for characterizing and confirming the synthesized NPs. The effect of biosynthesized CuO NPs (10 and 90 ppm), para-aminobenzoic acid (PABA) (20 ppm), and CuSO₄ (10 ppm) on the cell viability, biochemical properties, expression of TAT and GGPPS genes, and accumulation of taxol and baccatin III in hazelnut cell cultures was investigated. The results indicated that biosynthesized CuO NPs significantly influenced the cell viability, amount of ROS, antioxidant capacity, lipid peroxidation, secondary metabolite production, and expression pattern of the genes engaged in the biosynthesis pathway of taxanes in the C. avellana L. cells. The cytotoxicity of CuO NPs to cells was dose dependent and increased with increasing its concentration, as evidenced by a decline in the survival rate and cell membrane integrity. Furthermore, the utilization of 10 ppm CuSO₄ caused more toxicity in the cells than the same concentration of CuO NPs. This result could be attributed to the fact that plant extracts components act as a coating for the NPs and reduce their toxicity. Treatment of the cell cultures with CuO (10 ppm) + PABA (20 ppm) and CuO (10 ppm) induced the highest radical scavenging activity. The activity of antioxidant enzymes was increased with increasing the copper oxide NPs level from 10 to 90 ppm. Contrariwise, the cell's survival rate, radical scavenging activity, and amount of secondary metabolites were significantly reduced in the higher levels of copper oxide NPs (90 ppm) compared to the 10 ppm. The combined utilization of 10 ppm copper oxide NPs and 20 ppm PABA considerably stimulated the TAT and GGPPS genes expression and produced the highest amount of taxol and baccatin III. KEY POINTS: • CuO NPs were biologically synthesized using the hazel leaf extracts and confirmed by FTIR, XRD, EDAX, DLS, and SEM analyses. • CuO NPs significantly affected the amount of ROS, antioxidant capacity, and lipid peroxidation in C. avellana L. cells. • Treatment of the hazel cells with CuO NPs increased the production of secondary metabolites including taxol and baccatin III and expression of the genes involved in taxol and baccatin III biosynthesis (TAT and GGPPS).

Induction of Polyploidy and Metabolic Profiling in the Medicinal Herb Wedelia chinensis

Wedelia chinensis, which belongs to the Asteraceae family, is a procumbent, perennial herb. It has medicinal anti-inflammatory properties and has been traditionally used as folk medicine in East and South Asia for treating fever, cough and phlegm. In Taiwan, W. chinensis is a common ingredient of herbal tea. Previous studies showed that the plant leaves contain four major bioactive compounds, wedelolactone, demethylwedelolactone, luteolin and apigenin, that have potent antihepatoxic activity, and are thus used as major ingredients in phytopharmaceutical formulations. In this study, we set up optimal conditions for induction of ploidy in W. chinensis. Ploidy can be an effective method of increasing plant biomass and improving medicinal and ornamental characteristics. By using flow cytometry and chicken erythrocyte nuclei as a reference, the DNA content (2C) or genome size of W. chinensis was determined to be 4.80 picograms (pg) in this study for the first time. Subsequently, we developed the successful induction of five triploid and three tetraploid plants by using shoot explants treated with different concentrations (0, 0.25, 0.5, 1, 1.5, 2 g/L) of colchicine. No apparent morphological changes were observed between these polyploid plants and the diploid wild-type (WT) plant, except that larger stomata in leaves were found in all polyploid plants as compared to diploid WT. Ultra-performance liquid chromatography coupled with tandem mass spectrometry was used to quantify the four index compounds (wedelolactone, demethylwedelolactone, luteolin, apigenin) in these polyploid plants, and fluctuating patterns were detected. This is the first report regarding polyploidy in the herbal plant W. chinensis.

Application of Hairy Root Culture for Bioactive Compounds Production in Medicinal Plants

Medicinal plants are rich sources of natural bioactive compounds used to treat many diseases. With the development of the health industry, the market demands for Chinese medicine have been rapidly increasing in recent years. However, over-utilization of herbal plants would cause serious ecological problems. Therefore, an effective approach should be developed to produce the pharmaceutically important natural drugs. Hairy root culture induced by Agrobacterium rhizogenes has been considered to be an effective tool to produce secondary metabolites that are originally biosynthesized in the roots or even in the aerial organs of mature plants. This review aims to summarize current progress on medicinal plant hairy root culture for bioactive compounds production. It presents the stimulating effects of various biotic and abiotic elicitors on the accumulation of secondary metabolites. Synergetic effects by combination of different elicitors or with other strategies are also included. Besides, the transgenic system has promising prospects to increase bioactive compounds content by introducing their biosynthetic or regulatory genes into medicinal plant hairy root. It offers great potential to further increase secondary metabolites yield by the integration of manipulating pathway genes with elicitors and other strategies. Then advances on two valuable pharmaceuticals production in the hairy root cultures are illustrated in detail. Finally, successful production of bioactive compounds by hairy root culture in bioreactors are introduced.

Age-Dependent and Tissue-Specific Alterations in the rDNA Clusters of the Panax ginseng C. A. Meyer Cultivated Cell Lines

Long-term cultivation of Panax ginseng cell lines leads to a decreasing synthesis of the biologically active substances used in traditional medicine. To gain insight into the cellular mechanisms which may influence this process, we analyzed variations within the rDNA cluster of the Oriental ginseng cell lines. The cell lines were cultivated for 6 and 24 years; the number of nucleoli and chromosomes was analyzed. The complete 18S rDNA sequences were cloned and sequenced. The nucleotide polymorphism and phylogenetic relations of the sequences were analyzed, and the secondary structures for separate 18S rRNA regions were modeled. The 18S rDNA accumulated mutations during cell cultivation that correlate well with an increase in the number of chromosomes and nucleoli. The patterns of nucleotide diversity are culture-specific and the increasing polymorphism associates with cytosine methylation sites. The secondary structures of some 18S rRNA regions and their interaction can alter during cultivation. The phylogenetic tree topologies are particular for each cell line.The observed alterations in rDNA clusters are associated with a somaclonal variation, leading to changes in the pattern of intracellular synthesis during cell cultivation. The identified divergent rRNAs could provide additional gene expression regulation in P. ginseng cells by forming heterogeneous ribosomes.

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.

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.

An efficient plant regeneration and Agrobacterium-mediated genetic transformation of Tagetes erecta

Tagetes erecta, L. an asteraceous plant of industrial and medicinal value, contains important compounds like pyrethrins, thiophenes and lutein, possessing immense potential for insecticidal, nematicidal and nutraceutical activities. Considering the importance and demand for these natural compounds, genetic manipulation of this crop for better productivity of secondary metabolites holds great significance. A rapid and reproducible direct regeneration and genetic transformation system is the prerequisite for genetic manipulation of any crop. This paper elucidates the establishment of an efficient direct regeneration and transformation protocol of T. erecta using Agrobacterium tumefaciens. Investigation of the effects of different types of explants (Hypocotyls, cotyledonary leaves, rachis and leaf sections) and different BAP and GA3 combinations on the regeneration frequency of T. erecta suggested that the best regeneration frequency (66 %) with an average of 5.08 ± 0.09 shoot buds/explant was observed from hypocotyl explants cultured on media containing 1.5 mg/l BAP and 5 mg/l GA3. The transformation protocol was established using A. tumefaciens strain LBA4404, containing the binary vector pBI121, along with the gusA reporter gene with intron under the transcriptional control of the Cauliflower Mosaic Virus (CaMV) 35S promoter and the neomycin phosphotransferase II (nptII) gene as a kanamycin-resistant plant-selectable marker. Various parameters like optimization of kanamycin concentration (200 mg/l) for selection, standardization of cocultivation time (45 min) and acetosyringone concentration (150 μM) for obtaining higher transformation frequency were established using hypocotyl explants. The selected putative transgenic shoots were subsequently rooted on the Murashige and Skoog medium and transferred to the green house successfully. The plants were characterised by analysing the gus expression, amplification of 600 bp npt II fragment and Southern blot hybridization using the PCR-amplified gusA fragment as probe. The standardised protocol established during the study will open new vistas for genetic manipulation and introduction of desired genes for genetic improvement of T. erecta.

Indirect shoot organogenesis from leaf explants of Adhatoda vasica Nees

A novel protocol for indirect shoot organogenesis of Adhatoda vasica was developed using petiole explants derived from mature shrubby plants. Media with concentrations of cytokinins in combination with auxins were used to induce callus formation in two explants types: petiole and leaf segment. The frequency of callus formation from petiole and leaf segment explants on Murashige and Skoog (MS) basal medium supplemented with 0.25 mg l⁻¹ thidiazuron (TDZ) and 0.25 mg l⁻¹ α-naphthaleneacetic acid (NAA) was 100 ± 0.0 and 83.70 ± 0.52% respectively, while on this medium supplemented with 0.25 mg l⁻¹ 6-(γ-γ, dimethylallyamino purine) (2iP) and 0.25 mg l⁻¹ NAA, the callus frequency was 100 ± 0.0 and 96.70 ± 0.67% respectively. The highest shoot regeneration (90.60 ± 0.52%) response and the maximum shoots (8.10 ± 0.28) per callus were achieved from petiole explants on MS medium containing 0.25 mg l⁻¹ TDZ and 0.25 mg l⁻¹ NAA. On the contrary, on Schenk & Hildebrandt (SH) basal medium supplemented with 0.25 mg l⁻¹ TDZ and 0.25 mg l⁻¹ NAA, the frequency of callus formation from petiole and leaf segment explants was 100 ± 0.0 and 90.50 ± 0.89% respectively while the callus frequency on this medium containing 0.25 mg l⁻¹ 2iP and 0.25 mg l⁻¹ NAA was 100 ± 0.0 and 89.90 ± 0.72% respectively. The shoot regeneration frequency for petiole explants was 89.90 ± 0.46% producing 6.00 ± 0.21 shoots per callus on SH basal medium supplemented with 0.25 mg l⁻¹ TDZ and 0.25 mg l⁻¹ NAA. Whereas petiole explants could induce 83.70 ± 0.50% shoot regeneration and 7.3 ± 1.05 shoots per callus on SH medium containing 0.25 mg l⁻¹ indole-3-butyric acid (IBA), 0.5 mg l⁻¹ 6-benzyladenine (BA) and 0.5 mg l⁻¹ 2iP. Elongation of regenerated shoot was obtained on MS basal medium supplemented with 0.25 mg l⁻¹ TDZ. All regenerated shoots developed adventitious roots within 4 weeks when transferred to rooting medium containing SH medium supplemented with 0.5 mg l⁻¹ IBA. Total nine rooted plantlets were transferred from in vitro to in vivo conditions and eight plants survived and successfully acclimatized in the shaded greenhouse 12 weeks after transplanting.

Systems approaches to unraveling plant metabolism: identifying biosynthetic genes of secondary metabolic pathways

The diversity of useful compounds produced by plant secondary metabolism has stimulated broad systems biology approaches to identify the genes involved in their biosynthesis. Systems biology studies in non-model plants pose interesting but addressable challenges, and have been greatly facilitated by the ability to grow and maintain plants, develop laboratory culture systems, and profile key metabolites in order to identify critical genes involved their biosynthesis. In this chapter we describe a suite of approaches that have been useful in Actaea racemosa (L.; syn. Cimicifuga racemosa, Nutt., black coshosh), a non-model medicinal plant with no genome sequence and little horticultural information available, that have led to the development of initial gene-metabolite relationships for the production of several bioactive metabolites in this multicomponent botanical therapeutic, and that can be readily applied to a wide variety of under-characterized medicinal plants.

Efficient genetic transformation of Withania coagulans (Stocks) Dunal mediated by Agrobacterium tumefaciens from leaf explants of in vitro multiple shoot culture

An efficient and reproducible Agrobacterium-mediated genetic transformation of Withania coagulans was achieved using leaf explants of in vitro multiple shoot culture. The Agrobacterium strain LBA4404 harboring the binary vector pIG121Hm containing β-glucuronidase gene (gusA) under the control of CaMV35S promoter was used in the development of transformation protocol. The optimal conditions for the Agrobacterium-mediated transformation of W. coagulans were found to be the co-cultivation of leaf explants for 20 min to agrobacterial inoculum (O.D. 0.4) followed by 3 days of co-cultivation on medium supplemented with 100 μM acetosyringone. Shoot bud induction as well as differentiation occurred on Murashige and Skoog medium supplemented with 10.0 μM 6-benzylaminopurine, 8.0 μM indole 3-acetic acid, and 50.0 mgl(-1) kanamycin after three consecutive cycles of selection. Elongated shoots were rooted using a two-step procedure involving root induction in a medium containing 2.5 μM indole 3-butyric acid for 1 week and then transferred to hormone free one-half MS basal for 2 weeks. We were successful in achieving 100 % frequency of transient GUS expression with 5 % stable transformation efficiency using optimized conditions. PCR analysis of T0 transgenic plants showed the presence of gusA and nptII genes confirming the transgenic event. Histochemical GUS expression was observed in the putative transgenic W. coagulans plants. Thin layer chromatography showed the presence of similar type of withanolides in the transgenic and non-transgenic regenerated plants. A. tumefaciens mediated transformation system via leaf explants developed in this study will be useful for pathway manipulation using metabolic engineering for bioactive withanolides in W. coagulans, an important medicinal plant.

Genetically transformed roots: from plant disease to biotechnological resource

Hairy root syndrome is a disease that is induced by Agrobacterium rhizogenes infection and characterized by a proliferation of excessively branching roots. However, in the past 30 years A. rhizogenes-mediated transformation has also provided a valuable platform for studying biosynthesis pathways in plants. Furthermore, the genetically transformed root cultures are becoming increasingly attractive, cost-effective options for mass-producing desired plant metabolites and expressing foreign proteins. Numerous proof-of-concept studies have demonstrated the feasibility of scaling up hairy-root-based processes while maintaining their biosynthetic potential. Recently, hairy roots have also shown immense potential for applications in phytoremediation, that is, plant-based decontamination of polluted environments. This review highlights recent progress and limitations in the field, and outlines future perspectives for the industrial exploitation of hairy roots.

In vitro regeneration of wild chervil (Anthriscus sylvestris L.)

Anthriscus sylvestris (L.) Hoffm. (Apiaceae) is a common wild plant that accumulates the lignan deoxypodophyllotoxin. Deoxypodophyllotoxin can be hydroxylated at the C-7 position in recombinant organisms yielding podophyllotoxin, which is used as a semi-synthetic precursor for the anticancer drugs, etoposide phosphate and teniposide. As in vitro regeneration of A. sylvestris has not yet been reported, development of a regeneration protocol for A. sylvestris would be useful as a micropropagation tool and for metabolic engineering of the plant. Calli were induced from hypocotyl explants and transferred to shoot induction medium containing zeatin riboside. Regenerated shoots were obtained within 6 mo and were transferred onto growth regulator-free root induction medium containing 1% sucrose. Regenerated plants transferred to soil and acclimatized in a greenhouse. Plants were transferred to the field with a 100% survival rate. Regenerated plants flowered and were fully fertile. This is the first report of complete regeneration of A. sylvestris via shoot organogenesis from callus.

In vitro conservation of twenty-three overexploited medicinal plants belonging to the Indian sub continent

Twenty-three pharmaceutically important plants, namely, Elaeocarpus spharicus, Rheum emodi, Indigofera tinctoria, Picrorrhiza kurroa, Bergenia ciliata, Lavandula officinalis, Valeriana wallichii, Coleus forskohlii, Gentiana kurroo, Saussurea lappa, Stevia rebaudiana, Acorus calamus, Pyrethrum cinerariaefolium, Aloe vera, Bacopa monnieri, Salvia sclarea, Glycyrrhiza glabra, Swertia cordata, Psoralea corylifolia, Jurinea mollis, Ocimum sanctum, Paris polyphylla, and Papaver somniferum, which are at the verge of being endangered due to their overexploitation and collection from the wild, were successfully established in vitro. Collections were made from the different biodiversity zones of India including Western Himalaya, Northeast Himalaya, Gangetic plain, Western Ghats, Semiarid Zone, and Central Highlands. Aseptic cultures were raised at the morphogenic level of callus, suspension, axillary shoot, multiple shoot, and rooted plants. Synseeds were also produced from highly proliferating shoot cultures of Bacopa monnieri, Glycyrrhiza glabra, Stevia rebaudiana, Valeriana wallichii, Gentiana kurroo, Lavandula officinalis, and Papaver somniferum. In vitro flowering was observed in Papaver somniferum, Psoralea corylifolia, and Ocimum sanctum shoots cultures. Out of 23 plants, 18 plants were successfully hardened under glasshouse conditions.

Flavonoid biosynthesis genes putatively identified in the aromatic plant Polygonum minus via Expressed Sequences Tag (EST) analysis

P. minus is an aromatic plant, the leaf of which is widely used as a food additive and in the perfume industry. The leaf also accumulates secondary metabolites that act as active ingredients such as flavonoid. Due to limited genomic and transcriptomic data, the biosynthetic pathway of flavonoids is currently unclear. Identification of candidate genes involved in the flavonoid biosynthetic pathway will significantly contribute to understanding the biosynthesis of active compounds. We have constructed a standard cDNA library from P. minus leaves, and two normalized full-length enriched cDNA libraries were constructed from stem and root organs in order to create a gene resource for the biosynthesis of secondary metabolites, especially flavonoid biosynthesis. Thus, large-scale sequencing of P. minus cDNA libraries identified 4196 expressed sequences tags (ESTs) which were deposited in dbEST in the National Center of Biotechnology Information (NCBI). From the three constructed cDNA libraries, 11 ESTs encoding seven genes were mapped to the flavonoid biosynthetic pathway. Finally, three flavonoid biosynthetic pathway-related ESTs chalcone synthase, CHS (JG745304), flavonol synthase, FLS (JG705819) and leucoanthocyanidin dioxygenase, LDOX (JG745247) were selected for further examination by quantitative RT-PCR (qRT-PCR) in different P. minus organs. Expression was detected in leaf, stem and root. Gene expression studies have been initiated in order to better understand the underlying physiological processes.

Combinatorial genetic transformation of cereals and the creation of metabolic libraries for the carotenoid pathway

Combinatorial nuclear transformation is used to generate populations of transgenic plants containing random selections from a collection of input transgenes. This is a useful approach because it provides the means to test different combinations of genes without the need for separate transformation experiments, allowing the comprehensive analysis of metabolic pathways and other genetic systems requiring the coordinated expression of multiple genes. The principle of combinatorial nuclear transformation is demonstrated in this chapter through protocols developed in our laboratory that allow combinations of genes encoding enzymes in the carotenoid biosynthesis pathway to be introduced into rice and a white-endosperm variety of corn. These allow the accumulation of carotenoids to be screened initially by the colour of the endosperm, which ranges from white through various shades of yellow and orange depending on the types and quantities of carotenoids present. The protocols cover the preparation of DNA-coated metal particles, the transformation of corn and rice plants by particle bombardment, the regeneration of transgenic plants, the extraction of carotenoids from plant tissues, and their analysis by high-performance liquid chromatography.

A raison d'être for two distinct pathways in the early steps of plant isoprenoid biosynthesis?

When compared to other organisms, plants are atypical with respect to isoprenoid biosynthesis: they utilize two distinct and separately compartmentalized pathways to build up isoprene units. The co-existence of these pathways in the cytosol and in plastids might permit the synthesis of many vital compounds, being essential for a sessile organism. While substrate exchange across membranes has been shown for a variety of plant species, lack of complementation of strong phenotypes, resulting from inactivation of either the cytosolic pathway (growth and development defects) or the plastidial pathway (pigment bleaching), seems to be surprising at first sight. Hundreds of isoprenoids have been analyzed to determine their biosynthetic origins. It can be concluded that in angiosperms, under standard growth conditions, C₂₀-phytyl moieties, C₃₀-triterpenes and C₄₀-carotenoids are made nearly exclusively within compartmentalized pathways, while mixed origins are widespread for other types of isoprenoid-derived molecules. It seems likely that this coexistence is essential for the interaction of plants with their environment. A major purpose of this review is to summarize such observations, especially within an ecological and functional context and with some emphasis on regulation. This latter aspect still requires more work and present conclusions are preliminary, although some general features seem to exist.

Rotundifolone-induced relaxation is mediated by BK(Ca) channel activation and Ca(v) channel inactivation

Rotundifolone is the major constituent of the essential oil of Mentha x villosa Hudson. In preliminary studies, rotundifolone induced significant hypotensive, bradycardic and vasorelaxant effects in rats. Thus, to gain more insight into the pharmacology of rotundifolone, the aim of this study was to characterize the molecular mechanism of action involved in relaxation produced by rotundifolone. The relaxant effect was investigated in rat superior mesenteric arteries by using isometric tension measurements and whole-cell patch-clamp techniques. Rotundifolone relaxed phenylephrine-induced contractions in a concentration-dependent manner. Pre-treatment with KCl (20 mM), charybdotoxin (10(-7) M) or tetraethylammonium (TEA 10(-3) or 3 × 10(-3) M) significantly attenuated the relaxation effect induced by rotundifolone. Additionally, whole-cell patch-clamp recordings were made in mesenteric smooth muscle cells and showed that rotundifolone significantly increased K(+) currents, and this effect was abolished by TEA (10(-3)  M), suggesting the participation of BK(Ca) channels. Furthermore, rotundifolone inhibited the vasoconstriction induced by CaCl(2) in depolarizing nominally Ca(2+) -free medium and antagonized the contractions elicited by an L-type Ca(2+) channel agonist, S(-)-Bay K 8644 (2 × 10(-7)  M), indicating that the vasodilatation involved inhibition of Ca(2+) influx through L-type voltage-dependent calcium channels (Ca(v) type-L). Additionally, rotundifolone inhibited L-type Ca(2+) currents (I(Ca) L), affecting the voltage-dependent activation of I(Ca) L and steady-state inactivation. Our findings suggest that rotundifolone induces vasodilatation through two distinct but complementary mechanisms that clearly depend on the concentration range used. Rotundifolone elicits an increase in the current density of BK(Ca) channels and causes a shift in the steady-state inactivation relationship for Ca(v) type-L towards more hyperpolarized membrane potentials.

Mutation of Panax ginseng genes during long-term cultivation of ginseng cell cultures

It has previously been shown that the nucleotide sequences of the Agrobacterium rhizogenes rolC locus and the selective marker nptII developed mutations during the long-term cultivation of transgenic cell cultures of Panax ginseng. In the present report, we analyzed the nucleotide sequences of selected plant gene families in the 20-year-old P. ginseng 1c cell culture and in leaves of cultivated P. ginseng plants. We sequenced the Actin genes, which are a family of house-keeping genes; the phenylalanine ammonia-lyase (PAL) and dammarenediol synthase genes (DDS), which actively participate in the biosynthesis of ginsenosides; and the somatic embryogenesis receptor kinase (SERK) genes, which control plant development. We demonstrate that the plant genes also developed mutations during long-term cultivation. The highest level of nucleotide substitution was detected in the sequences of the SERK genes (2.00±0.11 nt per 1000 nt), and the level was significantly higher when compared with the cultivated P. ginseng plant. Interestingly, while the diversity of Actin genes was similar in the P. ginseng cell culture and the cultivated plants, the diversity of the DDS and SERK genes was less in the 20-year-old cell culture than in the cultivated plants. In this work, we detail the level of nucleotide substitutions in different plant genes during the long-term culture of plant cells.

Role of RNA interference in plant improvement

Research to alter crops for their better performance involving modern technology is underway in numerous plants, and achievements in transgenic plants are impacting crop improvements in unparalleled ways. Striking progress has been made using genetic engineering technology over the past two decades in manipulating genes from diverse and exotic sources, and inserting them into crop plants for inducing desirable characteristics. RNA interference (RNAi) has recently been identified as a natural mechanism for regulation of gene expression in all higher organisms from plants to humans and promises greater accuracy and precision to plant improvement. The expression of any gene can be down-regulated in a highly explicit manner exclusive of affecting the expression of any other gene by using RNAi technologies. Additional research in this field has been focused on a number of other areas including microRNAs, hairpin RNA, and promoter methylation. Manipulating new RNAi pathways, which generate small RNA molecules to amend gene expression in crops, can produce new quality traits and having better potentiality of protection against abiotic and biotic stresses. Nutritional improvement, change in morphology, or enhanced secondary metabolite synthesis are some of the other advantages of RNAi technology. In addition to its roles in regulating gene expression, RNAi is also used as a natural defense mechanism against molecular parasites such as jumping genes and viral genetic elements that affect genome stability. Even though much advancement has been made on the field of RNAi over the preceding few years, the full prospective of RNAi for crop improvement remains to be fully realized. The intricacy of RNAi pathway, the molecular machineries, and how it relates to plant development are still to be explained.

Amelioration of amyloid β-induced cognitive deficits by Zataria multiflora Boiss. essential oil in a rat model of Alzheimer's disease

INTRODUCTION

The limitations of current Alzheimer's disease (AD) therapeutics have prompted investigation into innovative therapeutics focused on antiinflammatory, antioxidant, and neuroprotective agents including those from medicinal plants. Numerous plants have been tested for their potential for alleviating symptoms of AD.

AIMS

Zataria multiflora Boiss. (ZM) a member of Lamiaceae family has been used in Iranian traditional medicine for its beneficial effects on mental abilities. Therefore, the effect of its essential oil was evaluated in a rat model of AD.

METHODS

Amyloid β-protein (Aβ) fragment 25-35 was injected bilaterally in the CA1 region of rats hippocampus and the effect of different doses of ZM essential oil (50, 100, or 200 μL/kg) on cognitive function was investigated in the Morris water maze. Acute toxicity of the essential oil was also studied.

RESULTS

The results showed increases in escape latency, traveled distance, heading angle, and decreases in target quadrant entries in Aβ-received groups as compared to the control group. This impairment was reversed by ZM essential oil. The results of acute toxicity testing revealed that the calculated LD50 (1264.9 μL/kg) is much higher than the therapeutic dose (100 μL/kg).

CONCLUSIONS

It seems that antioxidant, antiinflammatory, and anticholinesterase activities of ZM or its main constituents might contribute to its beneficial effects in this model. Our findings suggest that ZM may be a potentially valuable source of natural therapeutic agents for the treatment of AD. However, further investigations are necessary to establish its clinical efficacy and potential toxicity, before any recommendations concerning its use as a medication in the treatment of AD.

Enhanced production of a plant monoterpene by overexpression of the 3-hydroxy-3-methylglutaryl coenzyme A reductase catalytic domain in Saccharomyces cerevisiae

Linalool production was evaluated in different Saccharomyces cerevisiae strains expressing the Clarkia breweri linalool synthase gene (LIS). The wine strain T(73) was shown to produce higher levels of linalool than conventional laboratory strains (i.e., almost three times the amount). The performance of this strain was further enhanced by manipulating the endogenous mevalonate (MVA) pathway: deregulated overexpression of the rate-limiting 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase) doubled linalool production. In a haploid laboratory strain, engineering of this key step also improved linalool yield.

Agrobacterium tumefaciens-mediated transformation of Withania somnifera (L.) Dunal: an important medicinal plant

This report describes Agrobacterium tumefaciens-mediated transformation of Withania somnifera--an important Indian medicinal plant. A. tumefaciens strain LBA4404, containing the binary vector pIG121Hm was used for transformation, along with the gusA reporter gene with intron under the transcriptional control of the Cauliflower Mosaic Virus (CaMV) 35S promoter. The leaf segments from two-and-a-half-month-old green house-grown seedlings were more efficient in transformation, as compared to those from the in vitro-grown shoots. Second expanded leaf from the shoot tip gave the highest transient transformation efficiency. Selection of transgenic shoots was done in the presence of 50 mg l(-1) kanamycin. Polymerase chain reaction analysis of T(0) transgenic plants showed the presence of gusA and nptII genes. The expression of these transgenes in T(1) progeny was confirmed by RT-PCR. The integration of gusA gene was confirmed by Southern blot analysis. The transformation efficiency was found to be 1.67%.

Nucleotide substitutions in rolC and nptII gene sequences during long-term cultivation of Panax ginseng cell cultures

It has been shown previously that the rolC gene from Agrobacterium tumefaciens gene was stably and highly expressed in 15-year-old Panax ginseng transgenic cell cultures. In the present report, we analyze in detail the nucleotide composition of the rolC and nptII (neomycin phosphotransferase) genes, which is the selective marker used for transgenic cell cultures of P. ginseng. It has been established that the nucleotide sequences of the rolC and nptII genes underwent mutagenesis during cultivation. Particularly, 1-4 nucleotide substitutions were found per sequence in the 540 and 798 bp segments of the complete rolC and nptII genes, respectively. Approximately half of these nucleotide substitutions caused changes in the structure of the predicted gene product. In addition, we attempted to determine the rate of accumulation of these changes by comparison of DNA extracted from P. ginseng cell cultures from 1995 to 2007. It was observed that the frequency of nucleotide substitutions for the rolC and nptII genes in 1995 was 1.21 +/- 0.02 per 1,000 nucleotides analyzed, while in 2007, the nucleotide substitutions significantly increased (1.37 +/- 0.07 per 1,000 nucleotides analyzed). Analyzing the nucleotide substitutions, we found that substitution to G or to C nucleotides significantly increased (in 1.9 times) in the rolC and nptII genes compared with P. ginseng actin gene. Finally, the level of nucleotide substitutions in the rolC gene was 1.1-fold higher when compared with the nptII gene. Thus, for the first time, we have experimentally demonstrated the level of nucleotide substitutions in transferred genes in transgenic plant cell cultures.

Developing novel anthelmintics from plant cysteine proteinases

Intestinal helminth infections of livestock and humans are predominantly controlled by treatment with three classes of synthetic drugs, but some livestock nematodes have now developed resistance to all three classes and there are signs that human hookworms are becoming less responsive to the two classes (benzimidazoles and the nicotinic acetylcholine agonists) that are licensed for treatment of humans. New anthelmintics are urgently needed, and whilst development of new synthetic drugs is ongoing, it is slow and there are no signs yet that novel compounds operating through different modes of action, will be available on the market in the current decade. The development of naturally-occurring compounds as medicines for human use and for treatment of animals is fraught with problems. In this paper we review the current status of cysteine proteinases from fruits and protective plant latices as novel anthelmintics, we consider some of the problems inherent in taking laboratory findings and those derived from folk-medicine to the market and we suggest that there is a wealth of new compounds still to be discovered that could be harvested to benefit humans and livestock.

Biosynthesis of plant-derived flavor compounds

Plants have the capacity to synthesize, accumulate and emit volatiles that may act as aroma and flavor molecules due to interactions with human receptors. These low-molecular-weight substances derived from the fatty acid, amino acid and carbohydrate pools constitute a heterogenous group of molecules with saturated and unsaturated, straight-chain, branched-chain and cyclic structures bearing various functional groups (e.g. alcohols, aldehydes, ketones, esters and ethers) and also nitrogen and sulfur. They are commercially important for the food, pharmaceutical, agricultural and chemical industries as flavorants, drugs, pesticides and industrial feedstocks. Due to the low abundance of the volatiles in their plant sources, many of the natural products had been replaced by their synthetic analogues by the end of the last century. However, the foreseeable shortage of the crude oil that is the source for many of the artificial flavors and fragrances has prompted recent interest in understanding the formation of these compounds and engineering their biosynthesis. Although many of the volatile constituents of flavors and aromas have been identified, many of the enzymes and genes involved in their biosynthesis are still not known. However, modification of flavor by genetic engineering is dependent on the knowledge and availability of genes that encode enzymes of key reactions that influence or divert the biosynthetic pathways of plant-derived volatiles. Major progress has resulted from the use of molecular and biochemical techniques, and a large number of genes encoding enzymes of volatile biosynthesis have recently been reported.