Transgenic hairy roots

Bioreactor configurations for adventitious root culture: recent advances toward the commercial production of specialized metabolites

In vitro plant cell and organ cultures are appealing alternatives to traditional methods of producing valuable specialized metabolites for use as: pharmaceuticals, food additives, cosmetics, perfumes, and agricultural chemicals. Cell cultures have been adopted for the production of specialized metabolites in certain plants. However, in certain other systems, adventitious roots are superior to cell suspension cultures as they are organized structures that accumulate high levels of specialized metabolites. The cultivation of adventitious roots has been investigated in various bioreactor systems, including: mechanically agitated, pneumatically agitated, and modified bioreactors. The main relevance and importance of this work are to develop a long-lasting industrial biotechnological technology as well as to improve the synthesis of these metabolites from the plant in vitro systems. These challenges are exacerbated by: the peculiarities of plant cell metabolism, the complexity of specialized metabolite pathways, the proper selection of bioreactor systems, and bioprocess optimization. This review's major objective is to analyze several bioreactor types for the development of adventitious roots, as well as the advantages and disadvantages of each type of bioreactor, and to describe the strategies used to increase the synthesis of specialized metabolites. This review also emphasizes current advancements in the field, and successful instances of scaled-up cultures and the generation of specialized metabolites for commercial purposes are also covered.

Setting up Agrobacterium tumefaciens-mediated transformation of the tropical legume Aeschynomene evenia, a powerful tool for studying gene function in Nod Factor-independent symbiosis

Most legumes are able to develop a root nodule symbiosis in association with proteobacteria collectively called rhizobia. Among them, the tropical species Aeschynomene evenia has the remarkable property of being nodulated by photosynthetic Rhizobia without the intervention of Nod Factors (NodF). Thereby, A. evenia has emerged as a working model for investigating the NodF-independent symbiosis. Despite the availability of numerous resources and tools to study the molecular basis of this atypical symbiosis, the lack of a transformation system based on Agrobacterium tumefaciens significantly limits the range of functional approaches. In this report, we present the development of a stable genetic transformation procedure for A. evenia. We first assessed its regeneration capability and found that a combination of two growth regulators, NAA (= Naphthalene Acetic Acid) and BAP (= 6-BenzylAminoPurine) allows the induction of budding calli from epicotyls, hypocotyls and cotyledons with a high efficiency in media containing 0,5 μM NAA (up to 100% of calli with continuous stem proliferation). To optimize the generation of transgenic lines, we employed A. tumefaciens strain EHA105 harboring a binary vector carrying the hygromycin resistance gene and the mCherry fluorescent marker. Epicotyls and hypocotyls were used as the starting material for this process. We have found that one growth medium containing a combination of NAA (0,5 μM) and BAP (2,2 μM) was sufficient to induce callogenesis and A. tumefaciens strain EHA105 was sufficiently virulent to yield a high number of transformed calli. This simple and efficient method constitutes a valuable tool that will greatly facilitate the functional studies in NodF-independent symbiosis.

Discontinuous Translocation of a Luciferase Protein beyond Graft Junction in Tobacco

Transgrafting, a grafting technique that uses both genetically modified (GM) and non-GM plants, is a novel plant breeding technology that can be used to improve the efficiency of crop cultivation without introducing foreign genes into the edible parts of non-GM plants. This technique can facilitate the acquisition of disease resistance and/or increased yield. However, the translocation of low-molecular-weight compounds, ribonucleic acid (RNA), and proteins through graft junctions raises a potential safety risk for food crops. Here, we used a transgenic tobacco plant expressing a firefly luciferase gene (LUC) to examine the translocation of the LUC protein beyond the graft junction in grafted plants. We observed the bi-directional translocation of LUC proteins in transgrafted tobacco plants, i.e., from the rootstock to scion and vice versa. Transcriptomic analysis revealed that transcripts of the LUC gene were undetectable in non-GM plant bodies, indicating that the LUC protein itself was translocated. Moreover, the movement of the LUC protein is an episodic (i.e., non-continuous) event, since non-GM samples showing high LUC activity were flanked by non-GM samples showing no apparent LUC activity. Translocation from the GM to non-GM part depends on the characteristics of GM plant bodies; here, the enhanced translocation of the LUC protein into the non-GM scion was observed when LUC-expressing rootstocks with hairy roots were used. Moreover, the quantity of translocated LUC protein was far below the level that is generally required to induce an allergenic response. Finally, since the LUC protein levels of plants used for transgrafting are moderate and the LUC protein itself is relatively unstable, further investigation is necessary regarding whether the newly expressed protein in GM plants is highly stable, easily translocated, and/or highly expressed.

Production of species-specific anthocyanins through an inducible system in plant hairy roots

Anthocyanins are widely distributed pigments in flowering plants with red, purple or blue colours. Their properties in promoting heath make anthocyanins perfect natural colourants for food additives. However, anthocyanins with strong colour and stability at neutral pH, suitable as food colourants are relatively rare in nature. Acylation increases anthocyanin stability and confers bluer colour. In this study, we isolated two anthocyanin regulators SbMyb75 and SbDel from S. baicalensis, and showed that constitutive expression of the two TFs led to accumulation of anthocyanins at high levels in black carrot hairy roots. However, these hairy roots had severe growth problems. We then developed a β-estradiol inducible system using XVE and a Lex-35S promoter, to initiate expression of the anthocyanin regulators and induced this system in hairy roots of black carrot, tobacco and morning glory. Anthocyanins with various decorations were produced in these hairy roots without any accompanying side-effects on growth. We further produced highly acylated anthocyanins with blue colour in a 5 L liquid culture in a bioreactor of hairy roots from morning glory. We provide here a strategy to produce highly decorated anthocyanins without the need for additional engineering of any of the genes encoding decorating enzymes. This strategy could be transferred to other species, with considerable potential for natural colourant production for the food industries.

Induction and metabolomic analysis of hairy roots of Atractylodes lancea

Atractylodes lancea is an important source of traditional Chinese medicines. Sesquiterpenoids are the key active compounds in A. lancea, and their presence determines the quality of the material. Hairy hoot (HR) culture is a potential method to produce medicinally active compounds industrially; however, the induction and metabolic profiling of A. lancea HR have not been reported. We found that optimal induction of A. lancea HR was achieved by Agrobacterium rhizogenes strain C58C1 using the young leaves of tissue culture seedlings in the rooting stage as explants. Ultra-performance liquid chromatography-tandem mass spectrometric analyses of the chemical compositions of HR and normal root (NR) led to the annotation of 1046 metabolites. Over 200 differentially accumulated metabolites were identified, with 41 found to be up-regulated in HR relative to NR and 179 down-regulated in HR. Specifically, atractylodin levels were higher in HR, while the levels of β-eudesmol and hinesol were higher in NR. Metabolic pathway analyses showed a significant difference in metabolites of the shikimate acid pathway between HR and NR. Five A. lancea compounds are potential biomarkers for evaluation of HR and NR quality. This study provides an important reference for the application of HR for the production of medicinally active compounds. KEY POINTS: • We established an efficient protocol for the induction of HR in A. lancea • HR was found to have a significantly higher amount of atractylodin than did NRs • Metabolic pathway analyses showed a significant difference in metabolites of the shikimate acid pathway between HR and NR.

Hairy root culture: a potent method for improved secondary metabolite production of Solanaceous plants

Secondary metabolites synthesized by the Solanaceous plants are of major therapeutic and pharmaceutical importance, many of which are commonly obtained from the roots of these plants. 'Hairy roots', mirroring the same phytochemical pattern of the corresponding root of the parent plant with higher growth rate and productivity, are therefore extensively studied as an effective alternative for the in vitro production of these metabolites. Hairy roots are the transformed roots, generated from the infection site of the wounded plants with Agrobacterium rhizogenes. With their fast growth, being free from pathogen and herbicide contamination, genetic stability, and autotrophic nature for plant hormones, hairy roots are considered as useful bioproduction systems for specialized metabolites. Lately, several elicitation methods have been employed to enhance the accumulation of these compounds in the hairy root cultures for both small and large-scale production. Nevertheless, in the latter case, the cultivation of hairy roots in bioreactors should still be optimized. Hairy roots can also be utilized for metabolic engineering of the regulatory genes in the metabolic pathways leading to enhanced production of metabolites. The present study summarizes the updated and modern biotechnological aspects for enhanced production of secondary metabolites in the hairy root cultures of the plants of Solanaceae and their respective importance.

In Vitro Cultivation and Ginsenosides Accumulation in Panax ginseng: A Review

The use of in vitro tissue culture for herbal medicines has been recognized as a valuable source of botanical secondary metabolites. The tissue culture of ginseng species is used in the production of bioactive compounds such as phenolics, polysaccharides, and especially ginsenosides, which are utilized in the food, cosmetics, and pharmaceutical industries. This review paper focuses on the in vitro culture of Panax ginseng and accumulation of ginsenosides. In vitro culture has been applied to study organogenesis and biomass culture, and is involved in direct organogenesis for rooting and shooting from explants and in indirect morphogenesis for somatic embryogenesis via the callus, which is a mass of disorganized cells. Biomass production was conducted with different types of tissue cultures, such as adventitious roots, cell suspension, and hairy roots, and subsequently on a large scale in a bioreactor. This review provides the cumulative knowledge of biotechnological methods to increase the ginsenoside resources of P. ginseng. In addition, ginsenosides are summarized at enhanced levels of activity and content with elicitor treatment, together with perspectives of new breeding tools which can be developed in P. ginseng in the future.

Elicitation enhances the production of friedelin and epifriedelanol in hairy root cultures of Cannabis sativa L

Cannabis sativa L. (hemp) has a global distribution and social impact, and it is widely used as a medicinal plant, food ingredient, and textile fiber. Its roots have received less attention than other parts, especially the inflorescence, leaves, and shoots. Triterpenoids, including friedelin and epifriedelanol, have been found in hemp roots, and their anti-inflammatory effects have been reported. In this study, the potential enhancement of triterpenoid accumulation in the roots of C. sativa by elicitation was examined. Hairy roots were successfully established, and they contained 2.02-fold higher triterpenoid levels than natural roots. Furthermore, hairy roots treated with 75 μM salicylic acid had 1.95-fold higher friedelin levels (0.963 mg/g DW) and 1.4-fold higher epifriedelanol levels (0.685 mg/g DW) than untreated hairy roots. These results suggested that the elucidation of hairy root cultures using an optimized elicitor could represent an alternative strategy to produce the valuable triterpenoids friedelin and epifriedelanol.

Production of secondary metabolites using tissue culture-based biotechnological applications

Plants are the sources of many bioactive secondary metabolites which are present in plant organs including leaves, stems, roots, and flowers. Although they provide advantages to the plants in many cases, they are not necessary for metabolisms related to growth, development, and reproduction. They are specific to plant species and are precursor substances, which can be modified for generations of various compounds in different plant species. Secondary metabolites are used in many industries, including dye, food processing and cosmetic industries, and in agricultural control as well as being used as pharmaceutical raw materials by humans. For this reason, the demand is high; therefore, they are needed to be obtained in large volumes and the large productions can be achieved using biotechnological methods in addition to production, being done with classical methods. For this, plant biotechnology can be put in action through using different methods. The most important of these methods include tissue culture and gene transfer. The genetically modified plants are agriculturally more productive and are commercially more effective and are valuable tools for industrial and medical purposes as well as being the sources of many secondary metabolites of therapeutic importance. With plant tissue culture applications, which are also the first step in obtaining transgenic plants with having desirable characteristics, it is possible to produce specific secondary metabolites in large-scale through using whole plants or using specific tissues of these plants in laboratory conditions. Currently, many studies are going on this subject, and some of them receiving attention are found to be taken place in plant biotechnology and having promising applications. In this work, particularly benefits of secondary metabolites, and their productions through tissue culture-based biotechnological applications are discussed using literature with presence of current studies.

Effect of silver nanoparticles on tropane alkaloid production of transgenic hairy root cultures of Hyoscyamus muticus L. and their antimicrobial activity

The utilization of nanotechnology and biotechnology for enhancing the synthesis of plant bioactive chemicals is becoming increasingly common. The hairy root culture technique can be used to increase secondary metabolites such as tropane alkaloids. Agrobacterium was used to induce hairy roots from various explants of Hyoscyamus muticus. The effect of nano-silver particles (AgNPs) at concentrations of 0, 25, 50, 100, and 200 mg/L on tropane alkaloids synthesis, particularly hyoscyamine and scopolamine, was studied in transgenic hairy root cultures. Different types of explants obtained from 10-day-old seedlings of H. muticus were inoculated with two strains of Agrobacterium rhizogenes (15,834 and A4). The antimicrobial activity of an ethanolic extract of AgNPs-induced hairy root cultures of H. muticus was tested. The frequency of hairy roots was higher in hypocotyl, root, leaf, and stem explants treated with A. rhizogenes strain A4 compared to those treated with strain 15,834. In transgenic hairy root cultures, AgNPs application at a concentration of 100 mg/L resulted in the highest total tropane alkaloid production, which exhibited broad-spectrum antimicrobial activity. The study demonstrated the potential of nano-silver as an elicitor for promoting the production of target alkaloids in Hyoscyamus muticus hairy root cultures, which exhibit high biological activity.

Effect of Light Conditions on Polyphenol Production in Transformed Shoot Culture of Salvia bulleyana Diels

Various strategies have been used to increase the efficiency of secondary metabolite production in Salvia plants. This report is the first to examine the spontaneous development of Salvia bulleyana shoots transformed by Agrobacterium rhizogenes on hairy roots and the influence of light conditions on the phytochemical profile of this shoot culture. The transformed shoots were cultivated on solid MS medium with 0.1 mg/L of IAA (indole-3-acetic acid) and 1 mg/L of m-Top (meta-topolin), and their transgenic characteristic was confirmed by PCR-based detection of the rolB and rolC genes in the target plant genome. This study assessed the phytochemical, morphological, and physiological responses of the shoot culture under stimulation by light-emitting diodes (LEDs) with different wavelengths (white, WL; blue, B; red, RL; and red/blue, ML) and under fluorescent lamps (FL, control). Eleven polyphenols identified as phenolic acids and their derivatives were detected via ultrahigh-performance liquid chromatography with diode-array detection coupled to electrospray ionization tandem mass spectrometry (UPLC-DAD/ESI-MS) in the plant material, and their content was determined using high-performance liquid chromatography (HPLC). Rosmarinic acid was the predominant compound in the analyzed extracts. The mixed red and blue LEDs gave the highest levels of polyphenol and rosmarinic acid accumulation (respectively, 24.3 mg/g of DW and 20.0 mg/g of DW), reaching two times greater concentrations of polyphenols and three times greater rosmarinic acid levels compared to the aerial parts of two-year-old intact plants. Similar to WL, ML also stimulated regeneration ability and biomass accumulation effectively. However, the highest total photosynthetic pigment production (1.13 mg/g of DW for total chlorophyll and 0.231 mg/g of DW for carotenoids) was found in the shoots cultivated under RL followed by BL, while the culture exposed to BL was characterized as having the highest antioxidant enzyme activities.

Peat-based hairy root transformation using Rhizobium rhizogenes as a rapid and efficient tool for easily exploring potential genes related to root-knot nematode parasitism and host response

BACKGROUND

Root-knot nematodes (RKNs) pose a worldwide threat to agriculture of many crops including cucumber. Genetic transformation (GT) has emerged as a powerful tool for exploration of plant-RKN interactions and genetic improvement of RKN resistance. However, it is usually difficult to achieve a highly efficient and stable GT protocol for most crops due to the complexity of this process.

RESULTS

Here we firstly applied the hairy root transformation system in exploring root-RKN interactions in cucumber plants and developed a rapid and efficient tool transformation using Rhizobium rhizogenes strain K599. A solid-medium-based hypocotyl-cutting infection (SHI) method, a rockwool-based hypocotyl-cutting infection (RHI) method, and a peat-based cotyledon-node injection (PCI) method was evaluated for their ability to induce transgenic roots in cucumber plants. The PCI method generally outperformed the SHI and RHI methods for stimulating more transgenic roots and evaluating the phenotype of roots during nematode parasitism. Using the PCI method, we generated the CRISPR/Cas9-mediated malate synthase (MS) gene (involved in biotic stress responses) knockout plant and the LATERAL ORGAN BOUNDARIES-DOMAIN 16 (LBD16, a potential host susceptibility gene for RKN) promoter-driven GUS expressing plant. Knockout of MS in hairy roots resulted in effective resistance against RKNs, while nematode infection induced a strong expression of LBD16-driven GUS in root galls. This is the first report of a direct link between these genes and RKN performance in cucumber.

CONCLUSION

Taken together, the present study demonstrates that the PCI method allows fast, easy and efficient in vivo studies of potential genes related to root-knot nematode parasitism and host response.

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.

Collection of Hairy Roots as a Basis for Fundamental and Applied Research

Due to population growth, instability of climatic conditions, and reduction of the areas of natural ecosystems, it becomes necessary to involve modern biotechnological approaches to obtain highly productive plant material. This statement applies both to the creation of plant varieties and the production of new pharmaceutical raw materials. Genetic transformation of valuable medicinal plants using Agrobacterium rhizogenes ensures the production of stable and rapidly growing hairy roots cultures that have a number of advantages compared with cell culture and, above all, can synthesize root-specific substances at the level of the roots of the intact plant. In this regard, special attention should be paid to the collection of hairy roots of the Institute of Plant Physiology RAS, Russian Academy of Sciences, the founder of which was Dr. Kuzovkina I.N. Currently, the collection contains 38 hairy roots lines of valuable medicinal and forage plants. The review discusses the prospects of creating a hairy roots collection as a basis for fundamental research and commercial purposes.

Plants in vitro propagation with its applications in food, pharmaceuticals and cosmetic industries; current scenario and future approaches

Plant tissue culture technique employed for the identification and isolation of bioactive phytocompounds has numerous industrial applications. It provides potential benefits for different industries which include food, pharmaceutical and cosmetics. Various agronomic crops i.e., cereals, fruits, vegetables, ornamental plants and forest trees are currently being used for in vitro propagation. Plant tissue culture coupled with biotechnological approaches leads towards sustainable agricultural development providing solutions to major food security issues. Plants are the rich source of phytochemicals with medicinal properties rendering them useful for the industrial production of pharmaceuticals and nutraceuticals. Furthermore, there are numerous plant compounds with application in the cosmetics industry. In addition to having moisturizing, anti-ageing, anti-wrinkle effects; plant-derived compounds also possess pharmacological properties such as antiviral, antimicrobial, antifungal, anticancer, antioxidant, anti-inflammatory, and anti-allergy characteristics. The in vitro propagation of industrially significant flora is gaining attention because of its several advantages over conventional plant propagation methods. One of the major advantages of this technique is the quick availability of food throughout the year, irrespective of the growing season, thus opening new opportunities to the producers and farmers. The sterile or endangered flora can also be conserved by plant micro propagation methods. Hence, plant tissue culture is an extremely efficient and cost-effective technique for biosynthetic studies and bio-production, biotransformation, or bioconversion of plant-derived compounds. However, there are certain limitations of in-vitro plant regeneration system including difficulties with continuous operation, product removal, and aseptic conditions. For sustainable industrial applications of in-vitro regenerated plants on a large scale, these constraints need to be addressed in future studies.

Anticancer Secondary Metabolites: From Ethnopharmacology and Identification in Native Complexes to Biotechnological Studies in Species of Genus Astragalus L. and Gloriosa L

Some of the most effective anticancer compounds are still derived from plants since the chemical synthesis of chiral molecules is not economically efficient. Rapid discovery of lead compounds with pronounced biological activity is essential for the successful development of novel drug candidates. This work aims to present the chemical diversity of antitumor bioactive compounds and biotechnological approaches as alternative production and sustainable plant biodiversity conservation. Astragalus spp., (Fabaceae) and Gloriosa spp. (Liliaceae) are selected as research objects within this review because they are known for their anticancer activity, because they represent two of the largest families respectively in dicots and monocots, and also because many of the medicinally important plants are rare and endangered. We summarized the ethnobotanical data concerning their anticancer application, highlighted the diversity of their secondary metabolites possessing anticancer properties such as saponins, flavonoids, and alkaloids, and revealed the potential of the in vitro cultures as an alternative way of their production. Since the natural supply is limited, it is important to explore the possibility of employing plant cell or organ in vitro cultures for the biotechnological production of these compounds as an alternative.

Hairy Root Cultures as a Source of Polyphenolic Antioxidants: Flavonoids, Stilbenoids and Hydrolyzable Tannins

Due to their chemical properties and biological activity, antioxidants of plant origin have gained interest as valuable components of the human diet, potential food preservatives and additives, ingredients of cosmetics and factors implicated in tolerance mechanisms against environmental stress. Plant polyphenols are the most prominent and extensively studied, albeit not only group of, secondary plant (specialized) metabolites manifesting antioxidative activity. Because of their potential economic importance, the productive and renewable sources of the compounds are desirable. Over thirty years of research on hairy root cultures, as both producers of secondary plant metabolites and experimental systems to investigate plant biosynthetic pathways, brought about several spectacular achievements. The present review focuses on the Rhizobium rhizogenes-transformed roots that either may be efficient sources of plant-derived antioxidants or were used to elucidate some regulatory mechanisms responsible for the enhanced accumulation of antioxidants in plant tissues.

Improved and Highly Efficient Agrobacterium rhizogenes-Mediated Genetic Transformation Protocol: Efficient Tools for Functional Analysis of Root-Specific Resistance Genes for Solanum lycopersicum cv. Micro-Tom

Gene function analysis, molecular breeding, and the introduction of new traits in crop plants all require the development of a high-performance genetic transformation system. In numerous crops, including tomatoes, Agrobacterium-mediated genetic transformation is the preferred method. As one of our ongoing research efforts, we are in the process of mapping a broad-spectrum nematode resistance gene (Me1) in pepper. We work to transform tomato plants with candidate genes to confer resistance to nematodes in Solanaceae members. The transformation technology development is designed to produce a reproducible, rapid, and highly effective Agrobacterium-mediated genetic transformation system of Micro-Tom. In our system, a transformation efficiency of over 90% was achieved. The entire procedure, starting from the germination of seeds to the establishment of transformed plants in soil, was completed in 53 days. We confirmed the presence of the NeoR/KanR and DsRed genes in the transformed roots by polymerase chain reaction. The hairy root plants were infected with nematodes, and after 3 months, the presence of DsRed and NeoR/KanR genes was detected in the transformant roots to confirm the long-term effectiveness of the method. The presented study may facilitate root-related research and exploration of root–pathogen interactions.

Biotechnological approach for improvement of Crambe species as valuable oilseed plants for industrial purposes

Boosting technological innovation for a sustainable and circular bioeconomy encompasses the use of renewable materials and development of highly effective biotechnological approaches to improve the quality of oilseed crops and facilitate their industrial deployment. The interest in cultivating Crambe as a potential crop is steadily growing due to its low propensity to crossbreeding with other oilseed crops, valuable seed oil composition and a high yield capacity. The main focus is located on Crambe abyssinica as the most adapted into the agriculture and well-studied Crambe species. At the same time, the Crambe genus is one of the most numerous of the Brassicaceae family featuring several underestimated (orphaned) species with useful traits (abiotic stress tolerance, wide range of practical applications). This review features progress in the biotechnological improvement of well-adapted and wild Crambe species starting with aseptic culture establishment and plant propagation in vitro reinforced with the use of genetic engineering and breeding techniques. The aim of the paper is to highlight and review the existing biotechnological methods of both underestimated and well-adapted Crambe species improvment, including the establishment of aseptic culture, in vitro cultivation, plant regeneration and genetic transformation to modify seed oil content and morphological traits of valuable species.

Rhizobium rhizogenes-mediated root proliferation in Cd/Zn hyperaccumulator Sedum alfredii and its effects on plant growth promotion, root exudates and metal uptake efficiency

In this study, Rhizobium rhizogenes-mediated root proliferation system in Sedum alfredii has been established. Twenty strains of R. rhizogenes were screened for root proliferation. A significant difference (P < 0.01) was observed in plant morphological characters under influence of different bacterial strains. The highest root fresh weight (3.236 g/plant) was observed with strain AS12556. Furthermore, significant difference (P < 0.05) was observed in the chemical composition of organic acids, Tartaric acid (TA), Succinic acid (SA), Malic acid (MA), Citric acid (CA) and Oxalic acid (OA), pH, Total Nitrogen (TN), Total Organic Carbon (TOC) and soluble sugars in root exudates with different R. rhizogenes mediated roots. Furthermore, a series of hydroponics experiments were conducted with varying concentrations of Cd (25, 50 and 75 µM) and Zn (100, 200 and 500 µM) to assess the phytoextraction efficiency of proliferated roots with Rhizobium. Several plants with proliferated roots showed enhanced growth and improved metal extraction efficiency. Five strains (LBA 9402, K599, AS12556, MSU440 and C58C1) were identified as potential strains for root proliferation in Sedum alfredii. R. rhizogenes strain AS12556 improved Cd/Zn phytoextraction by exogenous production of phytochemicals to promote root proliferation, improved shoot biomass, lowered oxidative damage and enhanced phytoextraction efficiency in S. alfredii. Therefore, it has been selected as a potential microbial partner of S. alfredii to develop extensive rooting system for better growth and enhanced phytoremediation potential. Results suggest that R. rhizogenes mediated root proliferation system can be used for optimizing metal extraction from contaminated soils.

Spontaneous Regeneration of Plantlets Derived from Hairy Root Cultures of Lopezia racemosa and the Cytotoxic Activity of Their Organic Extracts

A histological analysis was performed with the aim of elucidating the spontaneous regeneration process of the hairy root lines LRT 2.3 and LRT 6.4, derived from Lopezia racemosa leaf explants and genetically transformed with the Agrobacterium rhizogenes strain ATCC15834/pTDT. The analysis showed both lines regenerate via indirect somatic embryogenesis; LRT 6.4 also regenerated by direct organogenesis. The morphogenic characteristics of the regenerated plantlets from both lines showed the typical characteristics, described previously, including a higher number of axillary shoot formation, short internodes, and plagiotropic roots compared with wild-type seedlings. The regeneration process occurred without the addition of plant growth regulators and was linked to the sucrose concentration in the culture medium. Reducing the sucrose concentration from 3% to 2%, 1%, and 0.5% increased the regeneration rate in LRT 6.4; the effect was less pronounced in LRT 2.3. The cytotoxic activity of different organic extracts obtained from roots and shoots were evaluated in the cancer cell lines HeLa (cervical carcinoma), HCT-15 (colon adenocarcinoma), and OVCAR (ovary carcinoma). The hexane and dichloromethane extracts from roots of both lines showed cytotoxic activity against the HeLa cell line. Only the dichloromethane extract from the roots of PLRT 2.3 showed cytotoxic activity against the OVCAR cell line. None of the methanol extracts showed cytotoxic activity, nor the shoot extracts from any solvent.

In vitro strategies for the enhancement of secondary metabolite production in plants: a review

BACKGROUND

Plants are the prime source of vital secondary metabolites (SMs) which are medicinally important for drug development, and these secondary metabolites are often used by plants in the various important tasks like defense against herbivory, interspecies defenses and against different types of stresses. For humans, these secondary metabolites are important as medicines, pigments, flavorings and drugs. Because most of the pharmaceutical industries are highly dependent on medicinal plants and their extraction, these medicinal plants are getting endangered.

MAIN BODY

Plant cell culture technologies are introduced as a viable mechanism for producing and studying SMs of plants. Various types of in vitro strategies (elicitation, hairy root culture system, suspension culture system, etc.) have been considerably used for the improvement of the production of SMs of plants. For the enhancement of SM production, suspension culture and elicitation are mainly used, but hairy root culture and other organ cultures are proved to satisfy the demand of secondary metabolites. Now, it is easy to control and manipulate the pathways that produce the plant secondary metabolites.

CONCLUSIONS

Techniques like plant cell, tissue and organ cultures provide a valuable method for the production of medicinally significant SMs. In recent years, most of the in vitro strategies are used due to knowledge and regulation of SM pathway in commercially valuable plants. In future, these things will provide a valuable method to sustain the feasibility of medicinal plants as the renewable sources of medicinally important compounds, and these methods will provide successful production of desired, important, valuable and also unknown compounds.

TRANSFORMATION MEDIATED BY Agrobacterium rhizogenes AS APPROACH OF STIMULATING THE SYNTHESIS OF ANTIOXIDANT COMPOUNDS IN Artemisia absinthium L

Artemisia absinthium L. plants are known as producers of substances with antioxidant properties. Among others, phenols and flavonoids are found in these plants. The synthesis of these bioactive compounds can be activated by genetic transformation. This process can be carried out even without the transfer of specific genes involved in the synthesis of flavonoids. Thus, “hairy” roots, obtained after Agrobacterium rhizogenes – mediated transformation, can produce a variety of valuable substances. The aim of the study was to obtaine A. absinthium “hairy” roots with high phenolic content. Methods. “Hairy” roots of plants were obtained by co-cultivation leaves with suspension of A. rhizogenes with pCB124 vector. The presence of transferred genes was confirmed by PCR. The reactions with AlCl3 and Folin-Ciocalteu reagent were used to determine the total flavonoids and phenols content. The antioxidant activity of extracts was evaluated by 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity. Results. PCR analysis detected the presence of bacterial rol genes and the absence of рСВ124 plasmid genes. Root lines differed in growth rate. “Hairy” roots were characterized by a higher phenolic content, particularly flavonoids (up to 4.784 ± 0.10 mg/g FW) compared to control (3.861±0.13 mg/g FW). Also, extracts from transgenic roots demonstrated higher antioxidant activity in the reaction with DPPH reagent (EC50 = 3.657 mg) when compared with extracts from control plants (EC50 = 6,716 mg). Conclusions. Transformation of A. absinthium mediated by A. rhizogenes can be applied for obtaining transgenic root lines with increased phenolic content and higher antioxidant activity.

Enhancement of Phytosterol and Triterpenoid Production in Plant Hairy Root Cultures-Simultaneous Stimulation or Competition?

Plant in vitro cultures, including hairy roots, can be applied for controlled production of valuable natural products, such as triterpenoids and sterols. These compounds originate from the common precursor squalene. Sterols and triterpenoids distinctly differ in their functions, and the 2,3-oxidosqualene cyclization step is often regarded as a branch point between primary and secondary (more aptly: general and specialized) metabolism. Considering the crucial role of phytosterols as membrane constituents, it has been postulated that unconstrained biosynthesis of triterpenoids can occur when sterol formation is already satisfied, and these compounds are no longer needed for cell growth and division. This hypothesis seems to follow directly the growth-defense trade-off plant dilemma. In this review, we present some examples illustrating the specific interplay between the two divergent pathways for sterol and triterpenoid biosynthesis appearing in root cultures. These studies were significant for revealing the steps of the biosynthetic pathway, understanding the role of particular enzymes, and discovering the possibility of gene regulation. Currently, hairy roots of many plant species can be considered not only as an efficient tool for production of phytochemicals, but also as suitable experimental models for investigations on regulatory mechanisms of plant metabolism.

Heterologous production of hyaluronic acid in Nicotiana tabacum hairy roots expressing a human hyaluronan synthase 2

Hyaluronic acid (HA), a unique polysaccharide with excellent Physico-chemical properties, is broadly used in pharmaceutical, biomedical, and cosmetic fields. It is widely present in all vertebrates, certain bacterial strains, and even viruses while it is not found in plants, fungi, and insects. HA is naturally synthesized by a class of integral membrane proteins called Hyaluronic acid synthase (HAS). Thus far, industrial production of HA is carried out based on either extraction from animal sources or large-scale microbial fermentation. The major drawbacks to using these systems are contamination with pathogens and microbial toxins. Recently, the production of HA through recombinant systems has received considerable attention. Plants are eco-friendly ideal expression systems for biopharmaceuticals production. In this study, the optimized human hyaluronic acid synthase2 (hHAS2) sequence was transformed into Nicotiana tabacum using Agrobacterium rhizogenes. The highest rhHAS2 concentration of 65.72 ng/kg (wet weight) in transgenic tobacco hairy roots was measured by the human HAS2 ELISA kit. The HA production in the transgenic hairy roots was verified by scanning electron microscope (SEM) and quantified by the HA ELISA kit. The DPPH radical scavenging activity of HA with the highest concentration of 0.56 g/kg (wet weight) showed a maximum activity of 46%. Gel Permeation Chromatography (GPC) analyses revealed the high molecular weight HA (HMW-HA) with about > 0.8 MDa.

Abietane Diterpenoids from the Hairy Roots of Salvia corrugata

Salvia corrugata Vahl. is an interesting source of abietane and abeo-abietane compounds that showed antibacterial, antitumor, and cytotoxic activities. The aim of the study was to obtain transformed roots of S. corrugata and to evaluate the production of terpenoids in comparison with in vivo root production. Hairy roots were initiated from leaf explants by infection with ATCC 15834 Agrobacterium rhizogenes onto hormone-free Murashige and Skoog (MS) solid medium. Transformation was confirmed by polymerase chain reaction analysis of rolC and virC1 genes. The biomass production was obtained in hormone-free liquid MS medium using Temporary Immersion System bioreactor RITA®. The chromatographic separation of the methanolic extract of the untransformed roots afforded horminone, ferruginol, 7-O-acetylhorminone and 7-O-methylhorminone. Agastol and ferruginol were isolated and quantified from the hairy roots. The amount of these metabolites indicated that the hairy roots of S. corrugata can be considered a source of these compounds.

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.

Ashwagandha: Advances in plant biotechnological approaches for propagation and production of bioactive compounds

ETHNOPHARMACOLOGICAL RELEVANCE

Withania somnifera is one of the most extensively delved Ayurvedic medicine. Apart from rejuvenation and increasing longevity, it has several other properties such as immunomodulation, anti-cancer, anti-stress and neuroprotection. Because of its prevailing use and increasing demand, it becomes prudent to scientifically evaluate and document both its propagation and production of desired phytoconstituents.

AIM OF THE STUDY

This review aims to highlight the research progress achieved on various biotechnological and tissue culture aspects of Withania somnifera and to cover up-to-date information regarding in-vitro propagation and production of withanolides.

MATERIALS AND METHODS

Significant published studies were identified for the years 2000-2018 using Elsevier-Science Direct, Pubmed and Google scholar and several research studies in our laboratory. Following keywords such as "plant extracts", "in vitro cultures", "callus and suspension culture", "micropropagation", "hairy root cultures" were used. Further, "Withania somnifera", "secondary metabolites specially withanolides", "molecular techniques" and "in vitro conservation" were used to cross-reference the keywords.

RESULTS

Ashwagandha comprises a broad spectrum of phytochemicals with a wide range of pharmacological properties. W. somnifera seeds have reduced viability and germination rates; thus, its regular cultivation method fails to achieve commercial demands mainly for the production of desired phytoconstituents. Cultivation of plant cells/tissues under in vitro conditions and development of various biotechnological strategies will help to build an attractive alternative to provide adequate quality and quantity raw materials. Recently, a large number of in vitro protocols has developed for W. somnifera not only for its propagation but for the production of secondary metabolites as well. Present work highlights a variety of biotechnological strategies both for prompt propagation and production of different bioactive secondary metabolites.

CONCLUSION

The present review focuses on the development and opportunities in various biotechnological approaches to accomplish the global demand of W. somnifera and its secondary metabolites. This review underlines the advances in plant biotechnological approaches for the propagation of W. somnifera and production of its bioactive compounds.

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.

Ethephon-induced changes in antioxidants and phenolic compounds in anthocyanin-producing black carrot hairy root cultures

Hairy root (HR) cultures are quickly evolving as a fundamental research tool and as a bio-based production system for secondary metabolites. In this study, an efficient protocol for establishment and elicitation of anthocyanin-producing HR cultures from black carrot was established. Taproot and hypocotyl explants of four carrot cultivars were transformed using wild-type Rhizobium rhizogenes. HR growth performance on plates was monitored to identify three fast-growing HR lines, two originating from root explants (lines NB-R and 43-R) and one from a hypocotyl explant (line 43-H). The HR biomass accumulated 25- to 30-fold in liquid media over a 4 week period. Nine anthocyanins and 24 hydroxycinnamic acid derivatives were identified and monitored using UPLC-PDA-TOF during HR growth. Adding ethephon, an ethylene-releasing compound, to the HR culture substantially increased the anthocyanin content by up to 82% in line 43-R and hydroxycinnamic acid concentrations by >20% in line NB-R. Moreover, the activities of superoxide dismutase and glutathione S-transferase increased in the HRs in response to ethephon, which could be related to the functionality and compartmentalization of anthocyanins. These findings present black carrot HR cultures as a platform for the in vitro production of anthocyanins and antioxidants, and provide new insight into the regulation of secondary metabolism in black carrot.

Plant hairy roots enable high throughput identification of antimicrobials against Candidatus Liberibacter spp

A major bottleneck in identifying therapies to control citrus greening and other devastating plant diseases caused by fastidious pathogens is our inability to culture the pathogens in defined media or axenic cultures. As such, conventional approaches for antimicrobial evaluation (genetic or chemical) rely on time-consuming, low-throughput and inherently variable whole-plant assays. Here, we report that plant hairy roots support the growth of fastidious pathogens like Candidatus Liberibacter spp., the presumptive causal agents of citrus greening, potato zebra chip and tomato vein greening diseases. Importantly, we leverage the microbial hairy roots for rapid, reproducible efficacy screening of multiple therapies. We identify six antimicrobial peptides, two plant immune regulators and eight chemicals which inhibit Candidatus Liberibacter spp. in plant tissues. The antimicrobials, either singly or in combination, can be used as near- and long-term therapies to control citrus greening, potato zebra chip and tomato vein greening diseases.

Increased phenolic acid and tanshinone production and transcriptional responses of biosynthetic genes in hairy root cultures of Salvia przewalskii Maxim. treated with methyl jasmonate and salicylic acid

The purpose of this study is to reveal the impact of the plant hormone salicylic acid (SA) and methyl jasmonate (MeJA) on the growth, effective components accumulation, and related gene expression of the hairy root of Salvia przewalskii Maxim. Various concentrations of SA (0, 25, 50, 100, 200 μM) or MeJA (0, 50, 100, 200, 400, 600 μM) were added to the culture medium of Salvia przewalskii Maxim. Low concentrations of SA promoted the growth of hairy root, while a high concentration inhibited it. 0 to 400 μM MeJA promoted the growth of hairy root, but 600 μM MeJA starts to inhibit its growth. 50 μM SA and 400 μM MeJA significantly enhanced the production of caffeic acid, rosmarinic acid, salvianolic acid B, cryptotanshinone, and tanshinone IIA. In general, 50 μM SA can be used to accumulate of tanshinone in hairy roots of S. przewalskii with 6 days. 400 μM MeJA can be used to accumulate of phenolic acids in hairy roots of S. przewalskii with 3 days. The selected genes in the tanshinone and phenolic acid biosynthetic pathway were upregulated with elicitation. To obtain a higher yield and content of secondary metabolites, it is advisable to use 50 μM SA or 400 μM MeJA as the optimal doses to cultivate the hairy root of S. przewalskii. This study provides, for the first time, an efficient tanshinone and phenolic acid production method for S. przewalskii.

Establishment of the hairy root culture of Echium plantagineum L. and its shikonin production

Echium plantagineum L. (Boraginaceae) is an invasive species in Australia and contains medicinal shikonins in its roots. In this study, the hairy root lines of E. plantagineum were established using Agrobacterium rhizogenes strain ATCC15834 and confirmed by the amplification of the rolB gene. Results showed significant difference in shikonin production between the hairy root lines in the ¹/₂B5 and M9 media. The biomass of the lines in the ¹/₂B5 medium was fivefold of that in the M9 medium. However, the components of detected shikonins were similar in these two liquid media. By contrast, different accumulation profiles appeared in the hairy root lines. HPLC analysis revealed the presence of nine possible related compounds, including shikonins, and acetylshikonin was the most abundant shikonin derivative. The content of acetylshikonin in the ¹/₂B5 medium (36.25 mg/L on average) was twofold of that in the M9 medium. Our results showed that the hairy root cultures of E. plantagineum can be used in enhancing the production of potential pharmaceutical compounds, such as acetylshikonin.

Biotransformation of xenobiotics by hairy roots

The exponential industrial growth we see today rides on the back of large scale production of chemicals, explosives and pharmaceutical products. However, the effluents getting released from their manufacturing units are greatly compromising the sustainability of our environment. With greater awareness of the imperative for environmental clean-up, a promising approach that is attracting increasing research interests is biodegradation of xenobiotics. In this approach, biotransformation has proven to be one of the most effective tools. While many different model frameworks have been used to study different aspects of biotransformation, hairy roots (HRs) have been found to be exceptionally valuable. HR cultures are preferred over other in-vitro model systems due to their biochemical stability and hormone-autotrophy. In addition, the multi-enzyme biosynthetic potential of HRs which is similar to the parent plant and their relatively low-cost cultural requirements further characterize their suitability for biotransformation. The recent progress observed in scale-up of HR cultures and understanding of functional genomics has opened up new dimensions providing valuable insights for industrial application. This review article summarizes the potential of HR cultures in the biotransformation of xenobiotics, their limitations in the application on a large scale and current strategies to alleviate them. Advancement in bioreactors engineering enabling large scale cultivation and modern gene technologies improving biotransformation efficiency promises to extend laboratory results to industrial applications.

Genetic Transformation in Peach (Prunus persica L.): Challenges and Ways Forward

Almost 30 years have passed since the first publication reporting regeneration of transformed peach plants. Nevertheless, the general applicability of genetic transformation of this species has not yet been established. Many strategies have been tested in order to obtain an efficient peach transformation system. Despite the amount of time and the efforts invested, the lack of success has significantly limited the utility of peach as a model genetic system for trees, despite its relatively short generation time; small, high-quality genome; and well-studied genetic resources. Additionally, the absence of efficient genetic transformation protocols precludes the application of many biotechnological tools in peach breeding programs. In this review, we provide an overview of research on regeneration and genetic transformation in this species and summarize novel strategies and procedures aimed at producing transgenic peaches. Promising future approaches to develop a robust peach transformation system are discussed, focusing on the main bottlenecks to success including the low efficiency of A. tumefaciens-mediated transformation, the low level of correspondence between cells competent for transformation and those that have regenerative competence, and the high rate of chimerism in the few shoots that are produced following transformation.

Segregation of rol Genes in Two Generations of Sinningia speciosa Engineered Through Wild Type Rhizobium rhizogenes

Rhizobium rhizogenes infects and transforms a wide range of plant species. It thereby introduces new genes located on transfer-DNA of the root inducing plasmid (pRi) into the plant genome and one of its abilities is to alter the host root system. Explants from pRi transformed roots from Sinningia speciosa were regenerated to create naturally transgenic Ri lines. The presence of rol and aux genes in the Ri lines was linked with altered growth characteristics: shorter peduncles, wrinkled leaves, delayed flowering and enhanced root growth. The potential of Ri lines for breeding was evaluated through consecutive backcrossing with the original host genotype. The progeny of reciprocal crosses showed non-Mendelian inheritance suggesting partial transmission of the of the aux and rol genes. The typical Ri phenotype observed in the primary Ri line was partially inherited. These results revealed that the Ri phenotype is a complex trait influenced by the genetic background of the Ri line.

Tinkering Cis Motifs Jigsaw Puzzle Led to Root-Specific Drought-Inducible Novel Synthetic Promoters

Following an in-depth transcriptomics-based approach, we first screened out and analyzed (in silico) cis motifs in a group of 63 drought-inducible genes (in soybean). Six novel synthetic promoters (SynP14-SynP19) were designed by concatenating 11 cis motifs, ABF, ABRE, ABRE-Like, CBF, E2F-VARIANT, G-box, GCC-Box, MYB1, MYB4, RAV1-A, and RAV1-B (in multiple copies and various combination) with a minimal 35s core promoter and a 222 bp synthetic intron sequence. In order to validate their drought-inducibility and root-specificity, the designed synthetic assemblies were transformed in soybean hairy roots to drive GUS gene using pCAMBIA3301. Through GUS histochemical assay (after a 72 h 6% PEG6000 treatment), we noticed higher glucuronidase activity in transgenic hairy roots harboring SynP15, SynP16, and SynP18. Further screening through GUS fluorometric assay flaunted SynP16 as the most appropriate combination of efficient drought-responsive cis motifs. Afterwards, we stably transformed SynP15, SynP16, and SynP18 in Arabidopsis and carried out GUS staining as well as fluorometric assays of the transgenic plants treated with simulated drought stress. Consistently, SynP16 retained higher transcriptional activity in Arabidopsis roots in response to drought. Thus the root-specific drought-inducible synthetic promoters designed using stimulus-specific cis motifs in a definite fashion could be exploited in developing drought tolerance in soybean and other crops as well. Moreover, the rationale of design extends our knowledge of trial-and-error based cis engineering to construct synthetic promoters for transcriptional upgradation against other stresses.

Establishment of hairy root cultures by Agrobacterium rhizogenes mediated transformation of Trachyspermum ammi L. for the efficient production of thymol

Trachyspermum ammi is an important medicinal plant that contains a bioactive compound namely thymol. In the study, T. ammi was transformed by Agrobacterium rhizogenes strains. Seedling stem explants were inoculated with A. rhizogenes strains A4, LBA 9402, ATCC 15834, and the effect of different co-cultivation media along with incorporation of acetosyringone (100 µM) was evaluated comparatively on the frequency of hairy root induction. The polymerase chain reaction using rolB and virD specific primers was served to confirm the putative transformed hairy roots. All strains established hairy root with various frequencies, among which strain ATCC 15834 was significantly the most efficient strain for hairy root induction (84.3%). Half-strength B5 medium and incorporation of acetosiryngone (100 µM) were also significantly optimal for hairy root induction. Hairy roots culture induced by ATCC 15834 using half-strength B5 liquid medium supplemented with 30 g L^-1 sucrose indicated the highest accumulation of biomass (99.05 g L^-1 FW and 10.95 g L^-1 DW) and thymol content (11.30 mg g^-1 DM) at 20 days. Nearly 4.9-fold and 5.3-fold increment of biomass and thymol accumulation was observed, respectively, at 20 days in comparison with the untransformed control roots. The results showed the high potential of T. ammi hairy roots for the biosynthesis of thymol.

‘Hairy’ root extracts as source for ‘green’ synthesis of silver nanoparticles and medical applications

The research was focused on the synthesis of silver nanoparticles (AgNPs) using extracts from the “hairy” root cultures of Artemisia tilesii Ledeb. and Artemisia annua L. The effect of operational parameters such as type of solvent, temperature of extraction, flavonoids concentration, and reducing power of the wormwood “hairy” root extracts on the particle size and yield of the resultant nanoparticles is reported for the first time. From the studied solvents, a water–ethanol mixture with a concentration of 70 vol% was found to be the best for the extraction of flavonoids from all “hairy” root cultures. The total flavonoid contents in A. annua and A. tilesii “hairy” root extracts were up to 80.0 ± 0.9 and 108 ± 4.4 mg RuE per g DW, respectively. Identification of flavonoids was confirmed by UPLC-ESI-UHR-Qq-TOF-MS analysis. Luteolin-7-β-d-glucopyranosid, isorhamnetin 3-O-glucoside, baicalein-7-O-glucuronide, apigenin-7-O-glucoside, quercetin, sitosterol, caffeoylquinic, galic, chlorogenic and caffeic acids were founded in the extracts. These extracts demonstrated the high reducing activities. Spherical, oval and triangular nanoparticles with effective sizes of 5–100 nm were observed. The TEM data revealed great differences in the shapes of NPs, obtained from the extracts from different root clones. The clustered and irregular NPs were found in the case of using ethanol extracts, mostly aggregated and having the size of 10–50 nm. The sizes of AgNPs decreased to 10–30 nm in the case of using aqueous extracts obtained at 80 °C. Biosynthesized AgNPs showed surface plasmon resonance in the range of 400–450 nm. The antimicrobial activity of the as-produced AgNPs was studied by disc diffusion method on Gram-positive (Staphylococcus aureus ATCC 25923 (F-49)), Gram-negative (Pseudomonas aeruginosa ATCC 27853 (F-51), Escherichia coli ATCC 25922 (F-50)) and Candida albicans ATCC 88-653 strains. It was found that the nanoparticles in some cases possessed the greater ability to inhibit microorganism growth compared to 1 mM AgNO₃ solution. The colloidal solutions of the obtained AgNPs were stable in the dark for 12 months at room temperature. Thus, the A. annua and A. tilesii “hairy” root extracts can be used for obtaining of bioactive AgNPs.

The research was focused on the synthesis of silver nanoparticles (AgNPs) using extracts from the “hairy” root cultures of Artemisia tilesii Ledeb. and Artemisia annua L.

The effect of purine-type cytokinin on the proliferation and production of phenolic compounds in transformed shoots of Dracocephalum forrestii

Dracocephalum forrestii is a perennial, endemic to China plant with a number of pharmaceutical properties. Transformed shoots of the species spontaneously regenerated from hairy roots induced by Agrobacterium rhizogenes. The transgenic nature of the shoots was confirmed by polymerase chain reaction (PCR). The shoot culture was multiplied on Murashige and Skoog (MS) medium with 0.2 mg/l IAA and 0.2, 0.5, 1.0, 2.0 or 5.0 mg/l purine-type cytokinins (mT, BAR, BPA or BAP). The highest multiplication rate (about thirteen shoot or buds per explant) was obtained on MS medium with 0.2 mg/l mT after four weeks of culture. The phenolic compounds present in the hydromethanolic extracts from the D. forrestii transgenic shoots were characterized using UPLC-PDA-ESI-MS. The shoots were found to biosynthesize three phenolic acids and five flavonoid glycosides. UHPLC analysis of the hydromethanolic extracts found the predominant phenolic acid to be rosmarinic acid, with its highest content observed in shoots cultivated with 5.0 mg/l BPA. In contrast, the greatest production of flavonoid derivatives (especially acacetin derivatives) was observed in the medium supplemented with 2 mg/l BPA.

Optimization of cell suspension culture of transformed and untransformed lettuce for the enhanced production of secondary metabolites and their pharmaceutical evaluation

In vitro suspension culture techniques are cost effective for large-scale production of secondary metabolites. In the present study, firstly, suspension cultures of untransformed Lactuca sativa were prepared using different hormonal combinations and were subjected to different pH, temperature and salt concentrations. Maximum biomass was obtained for suspensions supplemented with 1.5 mg/L BAP and 0.1 mg/L NAA, at pH 5.8, temperature 28 °C and 0 mM NaCl concentration. Using these parameters, suspensions were produced for rol ABC- and rol C-transformed lines of L. sativa. All the transgenic lines showed prominent increase in fresh weight (FW) and dry weight (DW) with maximum values for rol ABC2 line producing 169.8 mg/mL FW and 25.3 mg/mL DW. The exudates of transformed and untransformed plants were tested for the antioxidant activity and in vivo assays on rats. Maximum phenolic content (261 μg/mL) and flavonoid content (637.6 μg/mL) were obtained for rol C1 transgenic line. Total antioxidant capacity was found maximum (1451.7 μg/mL) for untransformed lettuce, whereas rol C1 showed maximum total reducing power activity (637.6 μg/mL). In DPPH assay, maximum activity (104.7 μg/mL) was shown by rol ABC3 line. In rats analgesic assay, maximum activity (74.9%) was shown by rol C2. Line rol C1 showed maximum anti-inflammatory activity (69.2%) and maximum antidepressant activity (minimum immobility time of 55 s). Maximum anticoagulant activity was observed for rol ABC2 with maximum clotting time of 130 s. The present study could help in using lettuce suspension culture as platform for the enhanced production of important metabolites.

Comparative analysis of glucosinolate production in hairy roots of green and red kale (Brassica oleracea var. acephala)

Glucosinolates (GSLs) are sulfur- and nitrogen-containing secondary metabolites that function in plant defense and provide benefits to human health. In this study, using Agrobacterium rhizogenes R1000, green and red kale hairy roots were established. The expression levels of GSLs biosynthesis genes and their accumulation in both kale hairy roots were analyzed by quantitative real-time PCR and HPLC. The results showed that the expression of most indolic GSLs biosynthesis genes was higher in the hairy roots of green kale than in that of red kale. In contrast, the expression of BoCYP83A1 and BoSUR1 encoding key enzymes aromatic GSL biosynthesis was significantly higher in red kale hairy root. The HPLC analysis identified six GSLs. The levels of 4-methoxyglucobrassicin, glucobrassicin, and 4-hydroxyglucobrassicin were 6.21, 5.98, and 2 times higher, respectively, in green kale than in red kale, whereas the levels of neoglucobrassicin and gluconasturtiin were 16.2 and 3.48 times higher, respectively, in red kale than in green kale. Our study provides insights into the underlying mechanisms of GSLs biosynthesis in kale hairy roots and can be potentially used as "biological factories" for producing bioactive substances such as GSLs.