Genetic transformation of Tylophora indica with Agrobacterium rhizogenes A4: growth and tylophorine productivity in different transformed root clones

Benzoindolizidine Alkaloids Tylophorine and Lycorine and Their Analogues with Antiviral, Anti-Inflammatory, and Anticancer Properties: Promises and Challenges

Ongoing viral research, essential for public health due to evolving viruses, gains significance owing to emerging viral infections such as the SARS-CoV-2 pandemic. Marine and plant alkaloids show promise as novel potential pharmacological strategies. In this narrative review, we elucidated the potential of tylophorine and lycorine, two naturally occurring plant-derived alkaloids with a shared benzoindolizidine scaffold, as antiviral agents to be potentially harnessed against respiratory viral infections. Possible structure-activity relationships have also been highlighted. The substances and their derivatives were found to be endowed with powerful and broad-spectrum antiviral properties; moreover, they were able to counteract inflammation, which often underpins the complications of viral diseases. At last, their anticancer properties hold promise not only for advancing cancer research but also for mitigating the oncogenic effects of viruses. This evidence suggests that tylophorine and lycorine could effectively counteract the pathogenesis of respiratory viral disease and its harmful effects. Although common issues about the pharmacologic development of natural substances remain to be addressed, the collected evidence highlights a possible interest in tylophorine and lycorine as antiviral and/or adjuvant strategies and encourages future more in-depth pre-clinical and clinical investigations to overcome their drawbacks and harness their power for therapeutic purposes.

Natural Products in Renal-Associated Drug Discovery

The global increase in the incidence of kidney failure constitutes a major public health problem. Kidney disease is classified into acute and chronic: acute kidney injury (AKI) is associated with an abrupt decline in kidney function and chronic kidney disease (CKD) with chronic renal failure for more than three months. Although both kidney syndromes are multifactorial, inflammation and oxidative stress play major roles in the diversity of processes leading to these kidney malfunctions. Here, we reviewed various publications on medicinal plants with antioxidant and anti-inflammatory properties with the potential to treat and manage kidney-associated diseases in rodent models. Additionally, we conducted a meta-analysis to identify gene signatures and associated biological processes perturbed in human and mouse cells treated with antioxidants such as epigallocatechin gallate (EGCG), the active ingredient in green tea, and the mushroom Ganoderma lucidum (GL) and in kidney disease rodent models. We identified EGCG- and GL-regulated gene signatures linked to metabolism; inflammation (NRG1, E2F1, NFKB1 and JUN); ion signalling; transport; renal processes (SLC12A1 and LOX) and VEGF, ERBB and BDNF signalling. Medicinal plant extracts are proving to be effective for the prevention, management and treatment of kidney-associated diseases; however, more detailed characterisations of their targets are needed to enable more trust in their application in the management of kidney-associated diseases.

Phenanthroindolizidine Alkaloids Secondary Metabolites Diversity in Medicinally Viable Plants of the Genus Tylophora

Plants of the genus Tylophora have commonly been used in traditional medicine in various communities, especially in the tropical and subtropical regions of climatic zones. Of the nearly 300 species reported in the Tylophora genus, eight are primarily used in various forms to treat a variety of bodily disorders based on the symptoms. Certain plants from the genus have found use as anti-inflammatory, anti-tumor, anti-allergic, anti-microbial, hypoglycemic, hypolipidemic, anti-oxidant, smooth muscle relaxant, immunomodulatory, and anti-plasmodium agents, as well as free-radical scavengers. Pharmacologically, a few plant species from the genus have exhibited broad-spectrum anti-microbial and anti-cancer activity, which has been proven through experimental evaluations. Some of the plants in the genus have also helped in alcohol-induced anxiety amelioration and myocardial damage repair. The plants belonging to the genus have also shown diuretic, anti-asthmatic, and hepato-protective activities. Tylophora plants have afforded diverse structural bases for secondary metabolites, mainly belonging to phenanthroindolizidine alkaloids, which have been found to treat several diseases with promising pharmacological activity levels. This review encompasses information on various Tylophora species, their distribution, corresponding plant synonyms, and chemical diversity of the secondary metabolic phytochemicals as reported in the literature, together with their prominent biological activities.

Production of rosmarinic acid and correlated gene expression in hairy root cultures of green and purple basil (Ocimum basilicum L.)

Rosmarinic acid (RA) is an active constituent of Ocimum basilicum. It has been shown that hairy root production (measured as dry weight) improves when green basil (O. basilicum "Cinnamon") is cultured under the light. In contrast, purple basil (O. basilicum "Purpurascens") shows greater hairy root production when cultured under dark conditions. The level of gene expression was highest in hairy roots of green basil under dark conditions for up to 1 week. Transcript levels were highest in hairy roots of purple basil under both dark and light conditions after 2 weeks of culturing. After 3 weeks of culture under light conditions, green basil had accumulated 1.9-fold higher RA content than that of purple basil, which in turn was fivefold higher than that of the natural roots (42.86 µg/mg). Tyrosine aminotransferase showed a higher transcript level when compared to the other phenylpropanoid pathway genes (phenylalanine ammonia-lyase, cinnamate 4-hydroxylase, and coenzyme-A ligase) in both dark and light conditions and in all-time regimens. RA accumulation was higher in the cultured hairy roots of green basil than those of purple basil under both light and dark conditions.

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.

Tylophorine: Sources, Properties, Applications and Biotechnological Production

Tylophora indica, a medicinal climber, belongs to the family, Asclepiadaceae. Roots and leaves of the plant contain several alkaloids including tylophorine, tylophorinine and tylophrinidine. The major alkaloid, tylophorine found in T. indica possesses several properties, such as immunosuppressive, antitumour, antifeedant, antibacterial, antifungal, antiamoebic, diuretic and hepatoprotective activities. In addition to this, tylophorine provides positive stimulation to adrenal cortex. Biotechnological production of tylophorine was fulfilled by inducing hairy roots mediated by Agrobacterium rhizogenes (A4 strain). It was followed by its growth in liquid suspension culture that could yield maximum biomass and tylophorine production. This type of liquid suspension culture yielded 9.8 ± 0.21 mgL⁻¹ tylophorine within 4–6 weeks of incubation. Maceration technique employed for the extraction of tylophorine was the most viable and efficient protocol. Although many reports are available regarding the biotechnological production of tylophorine, its competent and economic production still continues as a problematic issue.

Hairy root culture as a valuable tool for allelopathic studies in apple

Allelopathic plants exploit their chemical 'weapons' to prevail over the competition, suppress neighboring plants and consequently use the available resources more efficiently. However, the investigation of plant allelopathic interactions in rhizosphere is difficult to perform because of its high complexity due to interactions of biotic and abiotic factors. Thus, autonomous, aseptic root cultures of apple (Malus × domestica Borkh.) could facilitate allelopathic studies. We report on the successful genetic transformation of apple cultivars Melrose, Golden Delicious, Čadel and Gloster using Agrobacterium rhizogenes (Riker et al. 1930) Conn 1942 strain 15834 and for the first time the establishment of apple autonomous and permanent in vitro hairy root cultures that could be used as a new tool for apple allelopathic assays. Molecular characterization of transgenic hairy root lines was conducted to elucidate the possible relationship between expression of T-DNA genes and root growth characteristics that include branching. Similar content of phenolic acids (chlorogenic, caffeic, syringic, p-coumaric and ferulic), glycosilated flavonoids (rutin, quercitrin, isoquercitrin, kaempferol-3-glucoside) and flavonoid aglycones (quercetin and naringenin), and dihydrochalcone phloridzin, was detected in untransformed and transgenic apple root tissue by ultra high-performance liquid chromatography with mass spectrometry (UHPLC/(+/-)HESI-MS/MS) analyses, confirming that genetic transformation did not disturb secondary metabolite production in apple. Chlorogenic and caffeic acids and dihydrochalcones phloridzin and phloretin were detected as putative allelochemicals exuded into the growth medium in which transgenic roots were maintained for 4 weeks. Apple hairy root exudates significantly affected shoot and root development and growth of test plant Arabidopsis thaliana (L.) Heynh. seedlings after 5 or 10 days of treatment. Additionally, core cell-cycle genes CDKA1;1, CDKB2;1, CYCA3;1 and CYCB2;4 were down regulated in Arabidopsis shoots suggesting, in part, their role in inhibition of shoot growth. The present work highlighted an autonomous and permanent in vitro hairy root culture system as a valuable tool for studying allelopathic potential of apple, offering new perspective for allelopathy background elucidation in this important fruit species.

Influence of different Agrobacterium rhizogenes strains on hairy root induction and analysis of phenolic and flavonoid compounds in marshmallow (Althaea officinalis L.)

Hairy roots were induced in Althea officinalis using Agrobacterium rhizogenes, strains A4, A13, ATCC15834, and ATCC15834(GUS). The leaf, petiole and shoot explants of marshmallow were used for the hairy roots induction. When hairy roots appeared, cultures were established in MS (Murashige and Skoog) liquid medium without growth regulators. Hairy roots in explants appeared 5-12 days after inoculation. Maximum transformation frequency of 83% was observed on shoot explants with ATCC15834 strain. Among the strains, ATCC15834(GUS) strain showed better potential in the mass production of hairy roots in the hormone-free liquid medium after 50 days of culturing. The highest total phenolic and flavonoids content was found at 1.57 ± 0.1 mg/g dry weight in A13 strain and 3.47 ± 0.3 mg/g in A4 strain, respectively. Secondary metabolite content of hairy roots was found to be strain-specific.

Neoteric trends in tissue culture-mediated biotechnology of Indian ipecac [Tylophora indica (Burm. f.) Merrill]

Tylophora indica (Burm. f.) Merrill, an ethno-pharmacologically important perennial climber of Asclepiadaceae, is commonly known as Antamul or Indian ipecac. It is essentially accredited for its medicinal properties owing to its wide range of alkaloids in the form of bioactive secondary metabolites, such as tylophorine, tylophorinine, and tylophorinidine. Accelerated mass propagation of Tylophora is challenging because of its reduced seed germination frequency that consequently headed the pursuit for efficient protocols on in vitro propagation for the large-scale regeneration, conservation as well as sustainable supply of quality propagules. Ample tissue culture-mediated biotechnological investigations have been carried out on this medicinal plant till date and several micropropagation protocols have been standardized as well. The present review compares between several typical methods as well as factors, involving on direct and indirect organogenesis of Tylophora along with various up-to-date and modified techniques such as somatic embryogenesis, protoplast culture, synthetic seed production, genetic transformation, and in vitro interventions for the secondary metabolite production that have been reported in last two decades. This compilation will allow assessing the achievements and trends of Tylophora research so far, as well as will advance the research more rapidly, since many aspects, basic and applied, have yet to be explored.

Optimizing culture conditions for establishment of hairy root culture of Semecarpus anacardium L

Semecarpus anacardium L. is a tree species which produces secondary metabolites of medicinal importance. Roots of the plant have been traditionally used in folk medicines. Different strains of Agrobacterium rhizogenes (A4, ATCC15834 and LBA 9402) were used for induction of hairy roots in in vitro grown tissues of the plant. Hairy root initiation was observed after 25–30 days of infection. Optimum transformation frequency of 61% was achieved on leaf explants with ATCC15834 strain. Infection time of 30 min resulted in greater transformation frequency compared to 10 and 20 min, respectively. The hairy roots cultured in growth regulator-free semi-solid woody plant medium differentiated into callus. Whole shoots infected with ATCC 15834 were found to produce more transformants upon co-cultivation for 4 (65%) and 5 (67%) days. Induction of hairy roots in stem explants infected with ATCC 15834 was lower (52%) compared to leaves (62%) after 4 days of co-cultivation. In A4 and LBA9402 strains transformation efficiency was 49 ± 2.8% and 36 ± 5.7% in shoots after 4 days of co-cultivation. Transformation frequency was higher in ATCC15834 strain, irrespective of explants. The hairy roots of S. anacardium elongated slowly upon transfer to half-strength liquid medium. After 3–4 passages in liquid medium slender hairy roots started differentiating which were separated from the original explants. Visible growth of the roots was observed in hormone-free liquid medium after 2–3 months of culturing. Polymerase chain reaction with gene-specific primers from rol A, B and C genes confirms the positive transformation events.

Micropropagation and genetic transformation of Tylophora indica (Burm. f.) Merr.: a review

This review provides an in-depth and comprehensive overview of the in vitro culture of Tylophora species, which have medicinal properties. Tylophora indica (Burm. f.) Merr. is a climbing perennial vine with medicinal properties. The tissue culture and genetic transformation of T. indica, which has been extensively studied, is reviewed. Micropropagation using nodal explants has been reported in 25 % of all publications. Leaf explants from field-grown plants has been the explant of choice of independent research groups, which reported direct and callus-mediated organogenesis as well as callus-mediated somatic embryogenesis. Protoplast-mediated regeneration and callus-mediated shoot organogenesis has also been reported from stem explants, and to a lesser degree from root explants of micropropagated plants in vitro. Recent studies that used HPLC confirmed the potential of micropropagated plants to synthesize the major T. indica alkaloid tylophorine prior to and after transfer to field conditions. The genetic integrity of callus-regenerated plants was confirmed by RAPD in a few reports. Tissue culture is an essential base for genetic transformation studies. Hairy roots and transgenic T. indica plants have been shown to accumulate tylophorine suggesting that in vitro biology and transgenic methods are viable ways of clonally producing valuable germplasm and mass producing compounds of commercial value. Further studies that investigate the factors affecting the biosynthesis of Tylophora alkaloids and other secondary metabolites need to be conducted using non-transformed as well as transformed cell and organ cultures.

The Fate of Integrated Ri T-DNA rol Genes during Regeneration via Somatic Embryogenesis in Tylophora indica

The fate of integrated Ri T-DNA rol genes during regeneration via indirect somatic embryogenesis and stability of its effect on morphology and tylophorine content of Ri-transformed plants have been studied in Tylophora indica. Integration and expression of Ri T-DNA genes in transformed embryogenic callus lines derived from transformed root lines, 300 Ri-transformed somatic embryos, and 23 Ri-transformed plant lines were analysed. Fifty root lines studied showed integration and expression of four rol genes of TL-DNA. Spontaneous regeneration via indirect somatic embryogenesis was obtained from root lines that were TL+/TR−. Stable integration and expression of rol genes were observed in root lines, embryogenic callus lines, and the spontaneously induced somatic embryos. Nineteen out of the 23 Ri-transformed plant lines and their clones showed phenotypic and genetic stability over the period of 3 years. Four Ri-transformed plants were morphologically similar to nontransformed plants but showed variation with the integration and expression of the rolA gene and absence of other rol genes. Variant Ri-transformed plant line A428#1-V showed highest tylophorine content (2.93±0.03 mg gDW−1) among plant lines studied. The effects of T-DNA genes on growth, morphology, and tylophorine content of the Ri-transformed plants were stable in the long term culture.

Establishment of transgenic Rhazya stricta hairy roots to modulate terpenoid indole alkaloid production

Transgenic hairy roots of R. stricta were developed for investigation of alkaloid accumulations. The contents of five identified alkaloids, including serpentine as a new compound, increased compared to non-transformed roots. Rhazya stricta Decne. is a rich source of pharmacologically active terpenoid indole alkaloids (TIAs). In order to study TIA production and enable metabolic engineering, we established hairy root cultures of R. stricta by co-cultivating cotyledon, hypocotyl, leaf, and shoot explants with wild-type Agrobacterium rhizogenes strain LBA 9402 and A. rhizogenes carrying the pK2WG7-gusA binary vector. Hairy roots initiated from the leaf explants 2 to 8 weeks. Transformation was confirmed by polymerase chain reaction and in case of GUS clones with GUS staining assay. Transformation efficiency was 74 and 83% for wild-type and GUS hairy root clones, respectively. Alkaloid accumulation was monitored by HPLC, and identification was achieved by UPLC-MS analysis. The influence of light (16 h photoperiod versus total darkness) and media composition (modified Gamborg B5 medium versus Woody Plant Medium) on the production of TIAs were investigated. Compared to non-transformed roots, wild-type hairy roots accumulated significantly higher amounts of five alkaloids. GUS hairy roots contained higher amounts two of alkaloids compared to non-transformed roots. Light conditions had a marked effect on the accumulation of five alkaloids whereas the composition of media only affected the accumulation of two alkaloids. By successfully establishing R. stricta hairy root clones, the potential of transgenic hairy root systems in modulating TIA production was confirmed.

High-performance liquid chromatographic quantification of plumbagin from transformed rhizoclones of Plumbago zeylanica L.: inter-clonal variation in biomass growth and plumbagin production

An optimized protocol for induction and establishment of Agrobacterium rhizogenes-mediated hairy root cultures of Plumbago zeylanica L. was developed through selection of suitable explant type and the bacterial strain. The infection of internodal explants from an in vivo plant and leaves of in vitro origin with the A4 strain resulted in the emergence of hairy roots at a transformation frequency of 86.33 and 42.33 %, respectively. Independent transformed root somaclones (rhizoclones) capable of sustained growth were maintained under a low illumination in auxin-free agar-solidified Murashige and Skoog (MS) medium through subcultures at periodic intervals. The presence of pRi T L-DNA rolB or rolC genes and pRi T R-DNA mas2 gene in the transformed rhizoclone genome was ascertained by PCR amplification. Concentrations and type of carbon source, auxin and media strength were optimized for root biomass growth. Five independent rhizoclones each from A4- and LBA9402-transformed root lines were studied for their plumbagin accumulation at different growth phases, using HPLC analysis. The potential for plumbagin biosynthesis was expressed in all the tested rhizoclones, although distinct inter-clonal variations were noted. It was evident that maturation of hairy roots was more important for plumbagin accumulation; slow-growing and early-maturing rhizoclones accumulated more plumbagin compared to fast-growing and late-maturing rhizoclones. A4-induced rhizoclone HRA2B5 was identified as the most superior clone with a higher plumbagin yield potential in comparison with other tested hairy root clones, in vitro-grown non-transformed roots and in vivo roots of naturally occurring P. zeylanica.

Genetic elicitation by inducible expression of β-cryptogein stimulates secretion of phenolics from Coleus blumei hairy roots

The accumulation of phenolic compounds in plants is often part of the defense response against stress and pathogen attack, which can be triggered and activated by elicitors. Oomycetal proteinaceous elicitor, β-cryptogein, induces hypersensitive response and systemic acquired resistance against some pathogens. In order to test the effect of endogenously synthesized cryptogein protein on phenolic compounds accumulation in tissue, and secretion into the culture medium, Coleus blumei hairy roots were generated. Agrobacterium rhizogenes was employed to insert synthetic crypt gene, encoding β-cryptogein, under the control of alcohol-inducible promoter. The expression of β-cryptogein, in C. blumei hairy roots, was controlled by application of 1% and 2% ethanol, during 21 days induction period. Ethanol-induced expression of β-cryptogein caused significant decrease of soluble phenolics and rosmarinic acid (RA) in hairy root lines and increase of phenolics, RA and caffeic acid in culture medium. These data suggest that β-cryptogein might be a potential regulatory factor for phenolics secretion from the roots.

Use of the cryptogein gene to stimulate the accumulation of Bacopa saponins in transgenic Bacopa monnieri plants

Genetic transformation of the Indian medicinal plant, Bacopa monnieri, using a gene encoding cryptogein, a proteinaceous elicitor, via Ri and Ti plasmids, were established and induced bioproduction of bacopa saponins in crypt-transgenic plants were obtained. Transformed roots obtained with A. rhizogenes strain LBA 9402 crypt on selection medium containing kanamycin (100 mg l(-1)) dedifferentiated forming callus and redifferentiated to roots which, spontaneously showed shoot bud induction. Ri crypt-transformed plants thus obtained showed integration and expression of rol genes as well as crypt gene. Ti crypt-transformed B. monnieri plants were established following transformation with disarmed A. tumefaciens strain harboring crypt. Transgenic plants showed significant enhancement in growth and bacopa saponin content. Bacopasaponin D (1.4-1.69 %) was maximally enhanced in transgenic plants containing crypt. In comparison to Ri-transformed plants, Ri crypt-transformed plants showed significantly (p ≤ 0.05) enhanced accumulation of bacoside A(3), bacopasaponin D, bacopaside II, bacopaside III and bacopaside V. Produced transgenic lines can be used for further research on elicitation in crypt-transgenic plants as well as for large scale production of saponins. Key message The cryptogein gene, which encodes a proteinaceous elicitor is associated with increase in secondary metabolite accumulation-either alone or in addition to the increases associated with transformation by A. rhizogenes.

Use of Chenopodium murale L. transgenic hairy root in vitro culture system as a new tool for allelopathic assays

We investigated Chenopodium murale transgenic hairy root in vitro culture system as a new tool for allelopathic assays. Transgenic hairy roots were induced by Agrobacterium rhizogenes A4M70GUS from roots, cotyledons, leaves, and internodes of C. murale seedlings. Roots were found to be the best target explants, providing transformation efficiency of up to 11.1%. Established hairy root clones differed in their morphology and growth potential. Molecular characterization of these clones was carried out by PCR, RT-PCR and histochemical GUS analyses. No differences in rol gene expression were observed. Liquid culture system of characterized hairy root clones was maintained for over 2 years. Six hairy root clones were selected for assaying the allelopathic effect of their growth medium against germination and seedling elongation of wheat and lettuce test plants. The inhibitory potential varied depending on the hairy root clone. Some transgenic clones showed significantly higher inhibition compared to wild-type roots. These results revealed that hairy roots as an independent system synthesize some bioactive substances with allelopathic activity and exude them into the growth medium. Concentrations of caffeic, ferulic and p-coumaric acids (0.07-2.85 μmol/L) identified by HPLC analysis in the growth media were at least 1000 times lower than the inhibitory active concentration (5 mmol/L) of pure grade phenolic acids, suggesting that they have a limited role in the allelopathic phenomena of C. murale. The presented hairy root system appears to be a suitable tool for further investigation of the potential and nature of root-mediated allelopathic interference of C. murale.

Genetic transformation of Bacopa monnieri by wild type strains of Agrobacterium rhizogenes stimulates production of bacopa saponins in transformed calli and plants

We have developed an efficient transformation system for Bacopa monnieri, an important Indian medicinal plant, using Agrobacterium rhizogenes strains LBA 9402 and A4. Transformed roots induced by strain LBA 9402 spontaneously dedifferentiated to callus while excised roots induced by strain A4 spontaneously showed induction of shoot buds within 10 days. PCR and RT-PCR analysis revealed the presence and expression of the rolAB and rolC genes at the transcription level in pRi A4 transformed cultures indicating that the TL-DNA was integrated retained and expressed in the A4-Ri transformed shoots. Transformed calli showed the presence of rolAB or rol A, TR and ags genes. Transformed plants showed morphological features typically seen in transgenic plants produced by A. rhizogenes. Growth and biomass accumulation was significantly higher in the transformed shoots (twofold) and roots (fourfold) than in the non-transformed (WT) plants. In pRi A4-transformed plants, the content of bacopasaponin D, bacopasaponin F, bacopaside II and bacopaside V was enhanced significantly as compared to WT plants of similar age while bacoside A3 and bacopasaponin C content was comparable with that of WT plants. Significant increase in content of five bacopa saponins could be detected in pRi 9402-transformed callus cultures. There is an overall stimulatory effect on accumulation of bacopa saponins in transformed plants and cells of B. monnieri establishing the role of endogenous elicitation by Ri T-DNA of A. rhizogenes.

Determination of escin content in androgenic embryos and hairy root culture of Aesculus hippocastanum

Escin, a group of chemically related triterpenic glycosides, is widely used in commercial preparations for the treatment of venous insufficiency. Since the zygotic embryo cotyledons accumulate the highest amount of escin, it is currently extracted from the seeds of horse chestnut, Aesculus hippocastanum L. (Hippocastanaceae), on a large scale. As this material is available during only short period of the year, we studied the possibility of using plant tissue culture to obtain escin. For this purpose, the content of escin in androgenic embryos and hairy root cultures of horse chestnut was studied. Escin content was found to be dependent on the stage of androgenic embryo development and the type of phytoregulator supplemented to the nutritive medium. In the absence of phytoregulators, androgenic embryos at the globular stage of development contained approximately four times less escin than those at the cotyledonary stage. Inclusion of various phytoregulators in the nutritive media stimulated escin production. Among them, 2,4-dichlorophenoxyacetic acid (2,4-D) showed the most pronounced effect, with escin content almost reaching that found in zygotic embryos (6.77% versus 6.96%). Two hairy root clones produced substantial amounts of escin (3.57% and 4.09%), less than zygotic embryos, but higher than cotyledonary embryos on phytoregulator-free medium.

Agrobacterium rhizogenes-transformed roots of coffee (Coffea arabica): conditions for long-term proliferation, and morphological and molecular characterization

BACKGROUND AND AIMS

The aims of this study were to set up proliferation conditions for hairy roots of Coffea arabica regenerated after transformation by Agrobacterium rhizogenes strain A4-RS, and to carry out the morphological and molecular characterization of hairy root clones maintained over the long term.

METHODS

Auxin supply, light conditions and sucrose concentration were modified with the aim of establishing efficient root proliferation conditions. The morphological variability among 62 established hairy root clones was phenotyped by scanning the roots and analysing the images using 'whinRHIZO' software procedures. PCR analysis of integration in transformed root cells of rol and aux oncogenes from the T-DNA of the Ri plasmid was used to study the molecular variability among clones.

KEY RESULTS

Auxin supply was necessary to obtain and stimulate growth and branching, and IBA applied at 0.5 microm was the most efficient auxin. Significant differences were shown among the 62 clones for total root length and for the percentage of fine roots. These variables were stable across subcultures and could hence be used for efficient characterization of hairy root clones. The majority of hairy root clones (86 %) exhibited non-significant phenotype differences with non-transformed roots. Eight clones were significantly different from the non-transformed controls in that they possessed a low proportion of fine roots. Two other hairy root clones grew significantly faster than the other clones. The PCR analysis revealed a low variability in the integration of rol and aux oncogenes in transformed root cells. The T(R)-DNA was never integrated as aux1 and aux2 genes were not found, although rolB and rolC genes from the T(L)-DNA were always present.

CONCLUSIONS

The discovery of low morphological variability among coffee hairy roots together with the identification of morphological variables allowing easy identification of phenotypically altered clones represent two important results. They make hairy roots a possible, and efficient, tool for functional-genomic studies of coffee root genes.

The genetic manipulation of medicinal and aromatic plants

Medicinal and aromatic plants have always been intimately linked with human health and culture. Plant-derived medicines constitute a substantial component of present day human healthcare systems in industrialized as well as developing countries. They are products of plant secondary metabolism and are involved in many other aspects of a plant's interaction with its immediate environment. The genetic manipulation of plants together with the establishment of in vitro plant regeneration systems facilitates efforts to engineer secondary product metabolic pathways. Advances in the cloning of genes involved in relevant pathways, the development of high throughput screening systems for chemical and biological activity, genomics tools and resources, and the recognition of a higher order of regulation of secondary plant metabolism operating at the whole plant level facilitate strategies for the effective manipulation of secondary products in plants. Here, we discuss advances in engineering metabolic pathways for specific classes of compounds in medicinal and aromatic plants and we identify remaining constraints and future prospects in the field. In particular we focus on indole, tropane, nicotine, isoquinoline alcaloids, monoterpenoids such as menthol and related compounds, diterpenoids such as taxol, sequiterpenoids such as artemisinin and aromatic amino acids.

Changes in morphological phenotypes and withanolide composition of Ri-transformed roots of Withania somnifera

Developmental variability was introduced into Withania somnifera using genetic transformation by Agrobacterium rhizogenes, with the aim of changing withasteroid production. Inoculation of W. somnifera with A. rhizogenes strains LBA 9402 and A4 produced typical transformed root lines, transformed callus lines, and rooty callus lines with simultaneous root dedifferentiation and redifferentiation. These morphologically distinct transformed lines varied in T-DNA content, growth rates, and withasteroid accumulation. All of the lines with the typical transformed root morphology contained the T(L) T-DNA, and 90% of them carried the T(R) T-DNA, irrespective of the strain used for infection. Accumulation of withaferin A was maximum (0.44% dry weight) in the transformed root line WSKHRL-1. This is the first detection of withaferin A in the roots of W. somnifera. All of the rooty callus lines induced by strain A4 contained both the T(L) and the T(R)-DNAs. In contrast, 50% of the rooty-callus lines obtained with strain LBA 9402 contained only the T(R) T-DNA. All the rooty callus lines accumulated both withaferin A and withanolide D. The callusing lines induced by LBA 9402 lacked the T(L) T-DNA genes, while all the callusing lines induced by strain A4 contained the T(L) DNA. Four of these callus lines produced both withaferin A (0.15-0.21% dry weight) and withanolide D (0.08-0.11% dry weight), and they grew faster than the transformed root lines. This is the first report of the presence of withasteroids in undifferentiated callus cultures of W. somnifera.

Indolizidine and quinolizidine alkaloids

This review covers the isolation, structure determination, synthesis, chemical transformations and biological activity of indolizidine and quinolizidine alkaloids. Included in the review are the hydroxylated indolizidines lentiginosine, swainsonine, castanospermine and their analogues; alkaloids from animal sources, including ants, amphibians and beetles; indolizidine alkaloids from the genera Polygonatum, Prosopis and Elaeocarpus; indolizidine and phenanthroindolizidine alkaloids; alkylquinolizidine alkaloids, including myrtine, epimyrtine, plumerinine and Lycopodium metabolites; Lythraceae and Nuphar alkaloids; lupine alkaloids; and alkaloids from marine sources. 150 references are cited.

Spontaneous plant regeneration in transformed roots and calli from Tylophora indica: Changes in morphological phenotype and tylophorine accumulation associated with transformation by Agrobacterium rhizogenes

We examined the effects of genetic transformation by Agrobacterium rhizogenes on the production of tylophorine, a phenanthroindolizidine alkaloid, in the Indian medicinal plant, Tylophora indica. Transformed roots induced by the bacterium grew in axenic culture and produced shoots or embryogenic calli in the absence of hormone treatments. However, hormonal treatment was required to regenerate shoots in root explants of wild type control plants. Transformed plants showed morphological features typically seen in transgenic plants produced by A. rhizogenes, which include, short internodes, small and wrinkled leaves, more branches and numerous plagiotropic roots. Plants regenerated from transformed roots showed increased biomass accumulation (350-510% in the roots and 200-320% in the whole plants) and augmented tylophorine content (20-60%) in the shoots, resulting in a 160-280% increase in tylophorine production in different clones grown in vitro.

Efficient production of Agrobacterium rhizogenes-transformed roots and composite plants for studying gene expression in coffee roots

The possibility of rapid validation and functional analysis of nematode resistance genes is a common objective for numerous species and particularly for woody species. In this aim, we developed an Agrobacterium rhizogenes-mediated transformation protocol for Coffea arabica enabling efficient and rapid regeneration of transformed roots from the hypocotyls of germinated zygotic embryos, and the subsequent production of composite plants. The A. rhizogenes strain A4RS proved to be the most virulent. High transformation efficiencies (70%) were obtained using a 2-week co-cultivation period at a temperature of 15-18 degrees C. Using a p35S-gusA-int construct inserted in the pBIN19 binary plasmid, we could estimate that 35% of transformed roots were GUS positive (co-transformed). Using the GUS assay as visual marker, 40% composite plants bearing a branched co-transformed rootstock could be obtained after only 12 weeks without selection with herbicides or antibiotics. Transgenic coffee roots obtained with A. rhizogenes did not exhibit the 'hairy' disturbed phenotype and were morphologically similar to normal roots. PCR analyses demonstrated that all co-transformed roots were positive for the expected rolB and gusA genes. Transformed and non-transformed root systems from both susceptible and resistant varieties were inoculated with Meloidogyne exigua nematode individuals. Inoculation of composite plants from the Caturra susceptible variety resulted in the normal development of nematode larvae. Numbers of extracted nematodes demonstrated that transformed roots retain the resistance/sensibility phenotype of varieties from which they are derived. These results suggest that composite plants constitute a powerful tool for studying nematode resistance genes.