Improvement of hairy root cultures and plants by changing biosynthetic pathways leading to pharmaceutical metabolites: strategies and applications

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.

Insights into enhancing Centella asiatica organ cell biofactories via hairy root protein profiling

Recent advancements in plant biotechnology have highlighted the potential of hairy roots as a biotechnological platform, primarily due to their rapid growth and ability to produce specialized metabolites. This study aimed to delve deeper into hairy root development in C. asiatica and explore the optimization of genetic transformation for enhanced bioactive compound production. Previously established hairy root lines of C. asiatica were categorized based on their centelloside production capacity into HIGH, MID, or LOW groups. These lines were then subjected to a meticulous label-free proteomic analysis to identify and quantify proteins. Subsequent multivariate and protein network analyses were conducted to discern proteome differences and commonalities. Additionally, the quantification of rol gene copy numbers was undertaken using qPCR, followed by gene expression measurements. From the proteomic analysis, 213 proteins were identified. Distinct proteome differences, especially between the LOW line and other lines, were observed. Key proteins related to essential processes like photosynthesis and specialized metabolism were identified. Notably, potential biomarkers, such as the Tr-type G domain-containing protein and alcohol dehydrogenase, were found in the HIGH group. The presence of ornithine cyclodeaminase in the hairy roots emerged as a significant biomarker linked with centelloside production capacity lines, indicating successful Rhizobium-mediated genetic transformation. However, qPCR results showed an inconsistency with rol gene expression levels, with the HIGH line displaying notably higher expression, particularly of the rolD gene. The study unveiled the importance of ornithine cyclodeaminase as a traceable biomarker for centelloside production capacity. The strong correlation between this biomarker and the rolD gene emphasizes its potential role in optimizing genetic transformation processes in C. asiatica.

Identification and Functional Characterization of UDP-Glycosyltransferases Involved in Isoflavone Biosynthesis in Astragalus membranaceus

Isoflavones are rich natural compounds present in legumes and are essential for plant growth and development. Moreover, they are beneficial for animals and humans. Isoflavones are primarily found as glycoconjugates, including calycosin-7-O-β-d-glucoside (CG) in Astragalus membranaceus, a legume. However, the glycosylation mechanism of isoflavones in A. membranaceus remains unclear. In the present study, three uridine diphosphate (UDP)-glycosyltransferases (UGTs) that may be involved in the biosynthesis of isoflavone were identified in the transcriptome of A. membranaceus. Enzymatic analysis revealed that AmUGT88E29 and AmUGT88E30 had high catalytic activity toward isoflavones in vitro. In addition, AmUGT88E29 and AmUGT88E30 could accept various flavones, flavanones, flavonols, dihydroflavonols, and dihydrochalcones as substrates. AmUGT71G10 was only active against phloretin and dihydroresveratrol. Overexpression of AmUGT88E29 significantly increased the contents of CG, an isoflavone glucoside, in the hairy roots of A. membranaceus. This study provided candidate AmUGT genes for the potential metabolic engineering of flavonoid compounds in plants and a valuable resource for studying the calycosin glycosides biosynthesis pathway.

Phytochemical, Pharmacological, and Biotechnological Study of Ageratina pichinchensis: A Native Species of Mexico

Ageratina pichinchensis (Asteraceae) has been used for a long time in traditional Mexican medicine for treating different skin conditions and injuries. This review aimed to provide an up-to-date view regarding the traditional uses, chemical composition, and pharmacological properties (in vitro, in vivo, and clinical trials) that have been achieved using crude extracts, fractions, or pure compounds. Moreover, for a critical evaluation of the published literature, key databases (Pubmed, Science Direct, and SciFinder, among others) were systematically searched using keywords to retrieve relevant publications on this plant. Studies that reported on crude extracts, fractions, or isolated pure compounds of A. pichinchensis have found a varied range of biological effects, including antibacterial, curative, antiulcer, antifungal, and anti-inflammatory activities. Phytochemical analyses of different parts of A. pichinchensis revealed 47 compounds belonging to chromenes, furans, glycosylated flavonoids, terpenoids, and essential oils. Furthermore, biotechnological studies of A. pichinchensis such as callus and cell suspension cultures have provided information for future research perspectives to improve the production of valuable bioactive compounds.

A Brief Overview of Potential Treatments for Viral Diseases Using Natural Plant Compounds: The Case of SARS-Cov

The COVID-19 pandemic, as well as the more general global increase in viral diseases, has led researchers to look to the plant kingdom as a potential source for antiviral compounds. Since ancient times, herbal medicines have been extensively applied in the treatment and prevention of various infectious diseases in different traditional systems. The purpose of this review is to highlight the potential antiviral activity of plant compounds as effective and reliable agents against viral infections, especially by viruses from the coronavirus group. Various antiviral mechanisms shown by crude plant extracts and plant-derived bioactive compounds are discussed. The understanding of the action mechanisms of complex plant extract and isolated plant-derived compounds will help pave the way towards the combat of this life-threatening disease. Further, molecular docking studies, in silico analyses of extracted compounds, and future prospects are included. The in vitro production of antiviral chemical compounds from plants using molecular pharming is also considered. Notably, hairy root cultures represent a promising and sustainable way to obtain a range of biologically active compounds that may be applied in the development of novel antiviral agents.

Hairy root transformation of Brassica rapa with bacterial halogenase genes and regeneration to adult plants to modify production of indolic compounds

During the last years halogenated compounds have drawn a lot of attention. Metabolites with one or more halogen atoms are often more active than their non-halogenated derivatives like indole-3-acetic acid (IAA) and 4-Cl-IAA. Within this work, bacterial flavin-dependent tryptophan halogenase genes were inserted into Brassica rapa ssp. pekinensis (Chinese cabbage) with the aim to produce novel halogenated indole compounds. It was investigated which tryptophan-derived indole metabolites, such as indole glucosinolates or potential degradation products can be synthesized by the transgenic root cultures. In vivo and in vitro activity of halogenases heterologously produced was shown and the production of chlorinated tryptophan in transgenic root lines was confirmed. Furthermore, chlorinated indole-3-acetonitrile (Cl-IAN) was detected. Other tryptophan-derived indole metabolites, such as IAA or indole glucosinolates were not found in the transgenic roots in a chlorinated form. The influence of altered growth conditions on the amount of produced chlorinated compounds was evaluated. We found an increase in Cl-IAN production at low temperatures (8 °C), but otherwise no significant changes were observed. Furthermore, we were able to regenerate the wild type and transgenic root cultures to adult plants, of which the latter still produced chlorinated metabolites. Therefore, we conclude that the genetic information had been stably integrated. The transgenic plants showed a slightly altered phenotype compared to plants grown from seeds since they also still expressed the rol genes. By this approach we were able to generate various stably transformed plant materials from which it was possible to isolate chlorinated tryptophan and Cl-IAN.

Agrobacterium rhizogenes mediated transformation of Ficus carica L. for the efficient production of secondary metabolites

BACKGROUND

Ficus carica L., an ancient source of food and medicines, is rich in valuable nutritional and secondary compounds with antioxidant, antimicrobial, and anticancer effects. The present study is the first attempt to examine hairy root (HR) induction of F. carica (Sabz and Siah) by inoculating the 3-week-old shoots and leaves with different strains of Agrobacterium rhizogenes and also to investigate methyl jasmonate (MeJA) elicitation of HRs to produce a fast and high-yield production method for secondary metabolites.

RESULTS

The maximum transformation rate (100%) was achieved by inoculating the shoots with Agrobacterium rhizogenes strain A7. Siah HRs elicited with 100 and 200 μmol L^-1 MeJA and Sabz HRs with 100 μmol L^-1 MeJA showed the highest total phenolic content. The highest flavonoid content was 3.935 mg QE g^-1 DW in Siah HRs treated with 200 μmol L^-1 MeJA and 2.762 mg QE g^-1 DW in Sabz HRs treated with 300 μmol L^-1 MeJA. The 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity and ferric reducing antioxidant power (FRAP) value of HRs were affected by MeJA treatments. Methyl jasmonate elicitation also significantly enhanced the content of six phenolic acids (gallic acid, caffeic acid, chlorogenic acid, coumaric acid, rosmarinic acid, and cinnamic acid) and three flavonoids (rutin, quercetin, and apigenin). Thymol, a monoterpene phenol, was the main HR compound detected in gas chromatography mass spectrometry (GC-MS) analysis of the essential oils.

CONCLUSION

Induction of HRs and elicitation of F. carica HRs by MeJA resulted in a significant increase in the production of important phenolic compounds and a significant increase in antioxidant capacity. © 2020 Society of Chemical Industry.

Small-Scale Bioreactor for Sterile Hydroponics and Hairy Roots: Metabolic Diversity and Salicylic Acid Exudation by Hairy Roots of Hyoscyamus niger

The volume and complexity of commercial bioreactors for sterile hydroponics and hairy roots are too large for comparative analysis of many cultures. Here a small-scale bioreactor fabricated from standard glass materials and suitable for both airlift and bubble aeration mode is described. The performance of the bioreactor was tested by growing oilseed rape (Brassica napus L.) and rose plants (Rosa canina L.) in sterile hydroponics and by cultivating hairy roots of henbane (Hyoscyamus niger L.) and sesame (Hyoscyamus niger L.). Plants grown in hydroponics for up to six weeks did not show chloroses or necroses. Hairy roots grew faster or comparably fast in bioreactors as compared to shaking flasks. Root exudates of roses and exudates of hairy roots of henbane were subjected to targeted and nontargeted analysis by HPLC coupled with optical and mass spectrometric detectors. The diversity and concentration of hairy root exudates were higher in bioreactors than in shaking flasks. The composition of hairy root exudates of three accessions of H. niger did not match the genetic relatedness among the accessions. Hairy roots of Hyoscyamus niger exuded salicylic acid in amounts varying among plant accessions and between bioreactors and shaking flask cultures.

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.

Comparative analysis of glucosinolates and metabolite profiling of green and red mustard (brassica juncea) hairy roots

Here, accumulation of glucosinolates and expression of glucosinolates biosynthesis genes in green and red mustard hairy roots were identified and quantified by HPLC and qRT-PCR analyses. The total glucosinolates content of green mustard hairy root (10.09 µg/g dry weight) was 3.88 times higher than that of red mustard hairy root. Indolic glucosinolates (glucobrassicin, 4-methoxyglucobrassicin, and neoglucobrassicin) in green mustard were found at 30.92, 6.95, and 5.29 times higher than in red mustard hairy root, respectively. Conversely, levels of glucotropaeolin (aromatic glucosinolate) was significantly higher in red mustard than in green mustard. Accumulation of glucoraphasatin, an aliphatic glucosinolate, was only observed only in red mustard hairy roots. Quantitative real-time PCR analysis showed that the expression level of genes related to aliphatic and aromatic glucosinolate biosynthesis were higher in red mustard, exception BjCYP83B. The expression of BjCYP79B2, which encodes a key enzyme involved in the indolic glucosinolate biosynthetic pathway, was higher in green mustard than in red mustard. Additionally, to further distinguish between green mustard and red mustard hairy roots, hydrophilic and lipophilic compounds were identified by gas chromatography-mass spectrometry and subjected to principal component analysis. The results indicated that core primary metabolites and glucosinolate levels were higher in the hairy roots of green mustard than in those of red mustard.

Specialized Plant Metabolism Characteristics and Impact on Target Molecule Biotechnological Production

Plant secondary metabolism evolved in the context of highly organized and differentiated cells and tissues, featuring massive chemical complexity operating under tight environmental, developmental and genetic control. Biotechnological demand for natural products has been continuously increasing because of their significant value and new applications, mainly as pharmaceuticals. Aseptic production systems of plant secondary metabolites have improved considerably, constituting an attractive tool for increased, stable and large-scale supply of valuable molecules. Surprisingly, to date, only a few examples including taxol, shikonin, berberine and artemisinin have emerged as success cases of commercial production using this strategy. The present review focuses on the main characteristics of plant specialized metabolism and their implications for current strategies used to produce secondary compounds in axenic cultivation systems. The search for consonance between plant secondary metabolism unique features and various in vitro culture systems, including cell, tissue, organ, and engineered cultures, as well as heterologous expression in microbial platforms, is discussed. Data to date strongly suggest that attaining full potential of these biotechnology production strategies requires being able to take advantage of plant specialized metabolism singularities for improved target molecule yields and for bypassing inherent difficulties in its rational manipulation.

Transformed Root Culture: From Genetic Transformation to NMR-Based Metabolomics

Hairy root (HR) culture is considered as "green factory" for mass production of bioactive molecules with pharmaceutical relevance. As such, HR culture has an immense potential as a valuable platform to elucidate biosynthetic pathways and physiological processes, generate recombinant therapeutic proteins, assist molecular breeding, and enhance phytoremediation efforts. However, some plant species appear recalcitrant to the classical Agrobacterium rhizogenes transformation techniques. Sonication-assisted Agrobacterium-mediated transformation (SAArT) is a highly effective method to deliver bacteria to target plant tissues that includes exposure of the explants to short periods of ultrasound in the presence of the bacteria.Nuclear magnetic resonance (NMR)-based metabolomics is one of the most powerful and suitable platforms for identifying and obtaining structural information on a wide range of compounds with a high analytical precision. In terms of plant science, NMR metabolomics is used to determine the phytochemical variations of medicinal plants or commercial cultivars in certain environments and conditions, including biotic stress and plant biotic interaction, structural determination of natural products, quality control of herbal drugs or dietary supplements, and comparison of metabolite differences between plants and their respective in vitro cultures.In this chapter, we attempt to summarize our knowledge and expertise in induction of hairy roots from rare and recalcitrant plant species by SAArT technique and further methodology for extraction of secondary metabolites of moderate to high polarity and their identification by using NMR-based metabolomics.

Nitraria schoberi L. hairy root culture as a source of compounds with antiviral activity against influenza virus subtypes А(H5N1) and А(H3N2)

The hairy root culture of halophyte Nitraria schoberi was obtained by transforming seedlings' primary leaves with a wild strain of Agrobacterium rhizogenes 15834 SWISS (transformation frequency was 78.7%). The roots' transgenic status was confirmed by PCR analysis using rolB-, rolC-, virC-, virD1-specific primers. There was a significant increase in the biosynthesis of flavonoids, hydroxycinnamic acids, pectins, protopectins and saponins in hairy roots as compared to intact plant roots. The сatechin content in ethanol extracts of transformed roots' exceeded this factor 3.8 times in plant roots, but the compound composition of catechin nature in the latter was more diverse. The high antiviral activity of N. schoberi hairy root ethanol extracts against influenza virus subtypes A(H5N1), A(H3N2) was revealed, which manifested itself in the effective inhibition of infectivity both in vitro-in MDCK cell culture-and in vivo increasing survival of mice infected with them.

Elite hairy roots of Raphanus sativus (L.) as a source of antioxidants and flavonoids

An efficient protocol for hairy root induction in radish was established by optimizing several parameters that affect the efficiency of Agrobacterium rhizogenes-mediated transformations. Explants wounded using sterile hypodermic needle, infected with Agrobacterium suspension (0.6 OD600) for 10 min and co-cultivated in 1/2 MS medium containing acetosyringone (100 µM) for 2 days displayed maximum percentage of hairy root induction using MTCC 2364 (77.6%) and MTCC 532 (67.6%). On further experiments with MTCC 2364 initiated hairy roots, maximum biomass accumulation (fresh weight = 9.50 g; dry weight = 1.48 g) was achieved in liquid 1/2 MS medium supplemented with 87.6 mM sucrose after 40 days of culture. Transgenic state of hairy roots of MTCC 2364 was confirmed by polymerase chain reaction using rolB- and rolC-specific primers. The MTCC 2364-induced hairy roots produced higher amount of phenolic (33.0 mg g-1), flavonoid (48.0 mg g-1), and quercetin (114.8 mg g-1) content compared to auxin-induced roots of non-transformed radish. Furthermore, the results of ferric reducing antioxidant power and 1,1-diphenyl-2-picrylhydrazyl assay confirmed that the antioxidant activity of MTCC 2364 root extracts was improved when compared to auxin-induced roots of non-transformed radish. The present study offers a new insight in radish for production of phenolics and flavonoids (quercetin) using A. rhizogenes-mediated hairy root induction.

The Extracts of Morinda officinalis and Its Hairy Roots Attenuate Dextran Sodium Sulfate-Induced Chronic Ulcerative Colitis in Mice by Regulating Inflammation and Lymphocyte Apoptosis

Morinda officinalis is beneficial for the treatment of inflammatory bowel disease (IBD). The hairy root with higher genetic and biochemical stability cultured from M. officinalis might have similar effects to treat IBD. In this study, the main chemical composition of the root extracts of M. officinalis (MORE) native plant and the hairy root extract of M. officinalis (MOHRE) was compared by quantitative HPLC. The difference of their therapeutic effects and potential mechanism was evaluated using 3% dextran sodium sulfate-induced chronic colitis in mice and T lymphocytes in vitro. The results found that MOHRE possesses many specific peaks unobserved in the chromatogram of native plant. The content of iridoids in the MORE (3.10%) and MOHRE (3.01%) is somewhat similar but quite different for their anthraquinones’s content (0.14 and 0.66%, respectively). Despite all this, treatment with both MORE and MOHRE significantly attenuated the symptoms of colitis, including diarrhea, body weight loss, colon shortening, histological damage, and decreased inflammatory cytokine levels. In addition, they dose-dependently increased the apoptosis of T lymphocyte in vivo and in vitro. And, the differences for treatment effects on ulcerative colitis (UC) between them both in this study were mostly insignificant. The results demonstrated that the effects of MORE and MOHRE for the treatment of UC are similar, although there are a few difference on their chemical composition, indicating the hairy root cultured from M. officinalis might be able to replace its native plant on treatment of UC. The successful derivation of a sustainable hairy root culture provides a model system to study the synthetic pathways for bioactive metabolites, which will make the use of bioreactors to largely produce traditional medicine become reality.

Meristem Plant Cells as a Sustainable Source of Redox Actives for Skin Rejuvenation

Recently, aggressive advertisement claimed a “magic role” for plant stem cells in human skin rejuvenation. This review aims to shed light on the scientific background suggesting feasibility of using plant cells as a basis of anti-age cosmetics. When meristem cell cultures obtained from medicinal plants are exposed to appropriate elicitors/stressors (ultraviolet, ultrasound ultraviolet (UV), ultrasonic waves, microbial/insect metabolites, heavy metals, organic toxins, nutrient deprivation, etc.), a protective/adaptive response initiates the biosynthesis of secondary metabolites. Highly bioavailable and biocompatible to human cells, low-molecular weight plant secondary metabolites share structural/functional similarities with human non-protein regulatory hormones, neurotransmitters, pigments, polyamines, amino-/fatty acids. Their redox-regulated biosynthesis triggers in turn plant cell antioxidant and detoxification molecular mechanisms resembling human cell pathways. Easily isolated in relatively large quantities from contaminant-free cell cultures, plant metabolites target skin ageing mechanisms, above all redox imbalance. Perfect modulators of cutaneous oxidative state via direct/indirect antioxidant action, free radical scavenging, UV protection, and transition-metal chelation, they are ideal candidates to restore photochemical/redox/immune/metabolic barriers, gradually deteriorating in the ageing skin. The industrial production of plant meristem cell metabolites is toxicologically and ecologically sustainable for fully “biological” anti-age cosmetics.

Biolistic transformation of Scoparia dulcis L

Here, we report for the first time, the optimized conditions for microprojectile bombardment-mediated genetic transformation in Vassourinha (Scoparia dulcis L.), a Plantaginaceae medicinal plant species. Transformation was achieved by bombardment of axenic leaf segments with Binary vector pBI121 harbouring β-glucuronidase gene (GUS) as a reporter and neomycin phosphotransferase II gene (npt II) as a selectable marker. The influence of physical parameters viz., acceleration pressure, flight distance, gap width & macroprojectile travel distance of particle gun on frequency of transient GUS and stable (survival of putative transformants) expressions have been investigated. Biolistic delivery of the pBI121 yielded the best (80.0 %) transient expression of GUS gene bombarded at a flight distance of 6 cm and rupture disc pressure/acceleration pressure of 650 psi. Highest stable expression of 52.0 % was noticed in putative transformants on RMBI-K medium. Integration of GUS and npt II genes in the nuclear genome was confirmed through primer specific PCR. DNA blot analysis showed more than one transgene copy in the transformed plantlet genomes. The present study may be used for metabolic engineering and production of biopharmaceuticals by transplastomic technology in this valuable medicinal plant.

Ultraviolet Radiation-Elicited Enhancement of Isoflavonoid Accumulation, Biosynthetic Gene Expression, and Antioxidant Activity in Astragalus membranaceus Hairy Root Cultures

In this work, Astragalus membranaceus hairy root cultures (AMHRCs) were exposed to ultraviolet radiation (UV-A, UV-B, and UV-C) for promoting isoflavonoid accumulation. The optimum enhancement for isoflavonoid production was achieved in 34-day-old AMHRCs elicited by 86.4 kJ/m(2) of UV-B. The resulting isoflavonoid yield was 533.54 ± 13.61 μg/g dry weight (DW), which was 2.29-fold higher relative to control (232.93 ± 3.08 μg/g DW). UV-B up-regulated the transcriptional expressions of all investigated genes involved in isoflavonoid biosynthetic pathway. PAL and C4H were found to be two potential key genes that controlled isoflavonoid biosynthesis. Moreover, a significant increase was noted in antioxidant activity of extracts from UV-B-elicited AMHRCs (IC50 values = 0.85 and 1.08 mg/mL) in comparison with control (1.38 and 1.71 mg/mL). Overall, this study offered a feasible elicitation strategy to enhance isoflavonoid accumulation in AMHRCs and also provided a basis for metabolic engineering of isoflavonoid biosynthesis in the future.

Plant Cell, Tissue and Organ Culture: The Most Flexible Foundations for Plant Metabolic Engineering Applications

Significant advances in plant cell, tissue and organ culture (PCTOC) have been made in the last five decades. PCTOC is now thought to be the underlying technique for understanding general or specific biological functions of the plant kingdom, and it is one of the most flexible foundations for morphological, physiological and molecular biological applications of plants. Furthermore, the recent advances in the field of information technology (IT) have enabled access to a large amount of information regarding all aspects of plant biology. For example, sequencing information is stored in mega repositories such as the National Center for Biotechnology Information (NCBI), which can be easily accessed by researchers worldwide. To date, the PCTOC and IT combination strategy for regulation of target plant metabolism and the utilization of bioactive plant metabolites for commercial purposes is essential. In this review, the advantages and the limitations of these methodologies, especially regarding the production of bioactive plant secondary metabolites and metabolic engineering in target plants are discussed mainly from the phenotypic view point.

Plants and endophytes: equal partners in secondary metabolite production?

Well known plant production systems should be re-evaluated due to findings that the interesting metabolite might actually be produced by microbes intimately associated with the plant, so-called endophytes. Endophytes can be bacteria or fungi and they are characterized usually by the feature that they do not cause any harm to the host. Indeed, in some cases, such as mycorrhizal fungi or other growth promoting endophytes, they can be beneficial for the plant. Here some examples are reviewed where the host plant and/or endophyte metabolism can be induced by the other partner. Also, partial or complete biosynthesis pathways for plant secondary metabolites can be attributed to such endophytes. In other cases the host plant is able to metabolize substances from fungal origin. The question of the natural role of such metabolic changes for the endophyte will be briefly touched. Finally, the consequences for the use of plant cultures for secondary metabolite production is discussed.

Efficient production of isoflavonoids by Astragalus membranaceus hairy root cultures and evaluation of antioxidant activities of extracts

In this study, Astragalus membranaceus hairy root cultures (AMHRCs) were established as an attractive alternative source for the efficient production of isoflavonoids (IF). A. membranaceus hairy root line II was screened as the most efficient line and was confirmed by PCR amplification of rolB, rolC and aux1 genes. Culture parameters of AMHRCs were systematically optimized, and five main IF constituents were quali-quantitatively determined by LC-MS/MS. Under optimal conditions, the total IF accumulation of 34 day old AMHRCs was 234.77 μg/g dry weight (DW). This yield was significantly higher compared to that of 3 year old field grown roots (187.38 μg/g DW). Additionally, in vitro antioxidant assays demonstrated that AMHRC extracts exhibited antioxidant activities with lower IC50 values (1.40 and 1.73 mg/mL) as compared to those of field grown roots (1.96 and 2.17 mg/mL). Overall, AMHRCs may offer a promising and continuous product platform for naturally derived, high quality and valuable nutraceuticals.