Agrobacterium rhizogenes-mediated transformation enhances the antioxidant potential of Artemisia tilesii Ledeb

Efficient hairy root induction system of Astragalus membranaceus and significant enhancement of astragalosides via overexpressing AmUGT15

KEY MESSAGE

Astragalus membranaceus hairy roots induced by direct injection of Rhizobium rhizogenes with AmUGT15 overexpressing genes into the stem explants demonstrate enhanced astragaloside biosynthesis Astragalus membranaceus is a widely used medicinal plant, which has important economic, ecological, medicinal, and ornamental values for accumulating various triterpene saponins named astragalosides in roots. Although the hairy root culture technique has been established in A. membranaceus, the molecular regulation of metabolic pathways for improving astragaloside contents was not reported. In this study, an efficient hairy root induction method was established in A.membranaceus by directly injecting Rhizobium rhizogenes into the stem, with an induction rate of up to 80.1%. We improved the production of astragaloside in hairy roots by overexpressing AmUGT15, a 3-O-glucosyltransferase catalyzed xylosylation at C3-OH. The fluorescence microscopy observation revealed that the AmUGT15 fused with DsRed report gene constructed in T-DNA region was overexpressed in hairy roots, and the maximum biomass of hairy roots was measured on the 28th day of cultivation. HPLC analysis confirmed the total amount of astragalosides produced by AmUGT15 overexpressing hairy roots is 4.2 times higher than the non-transgenic control group. Our study proposed an effective method for astragalosides production in A. membranaceus hairy roots via metabolic engineering.

Study of Superoxide Dismutase Activity in Long-Term Cultivated Artemisia and Althaea "hairy" Roots

The aim of the study was to evaluate the long-term effect of Agrobacterium rhizogenes genes transfer on plant antioxidant system by the study of superoxide dismutase (SOD) activity in "hairy" roots of Artemisia and Althaea spp plants. PCR analyses revealed stability of the transformation and presence of bacterial rol B and rol C genes in the "hairy" roots after 4-6 years from the transformation event. SOD activity in the roots of untransformed in vitro cultivated plants used for the initiation of "hairy" roots growth was in the range of 45.8 ± 8.7 U/μg (Althaea officinalis) and 275 ± 97.1 U/μg (Artemisia ludoviciana). After a long-term in vitro cultivation more than half of tested "hairy" root lines (54%) showed a significant increase in SOD activity values compared to untransformed roots. The highest SOD activity values of "hairy" root lines (24-fold increase) were founded in A. officinalis (1105 ± 174 U/μg) and A. dracunculus (1356 ± 402 U/μg). The increase of the activity was found also in "hairy" roots of A. vulgaris (up to 375 ± 28.2 U/μg, sevenfold increase), A. ludoviciana (1001 ± 191 U/μg, 3.6-fold increase), and A. tilesii (438 ± 104 U/μg, 1.6-fold increase). The results of our study indicate that transformation by wild-type A. rhizogenes not harboring any foreign genes implementing in SOD activity regulation can often stably activate plant antioxidant enzyme system. This effect, observed in the "hairy" roots of five plant species in 4-6 years of the transformation event, obviously, should be taken into account in works aimed at creating transgenic plants by Agrobacterium-mediated transformation.

Response of physiological parameters in Dionaea muscipula J. Ellis teratomas transformed with rolB oncogene

BACKGROUND

Plant transformation with rol oncogenes derived from wild strains of Rhizobium rhizogenes is a popular biotechnology tool. Transformation effects depend on the type of rol gene, expression level, and the number of gene copies incorporated into the plant's genomic DNA. Although rol oncogenes are known as inducers of plant secondary metabolism, little is known about the physiological response of plants subjected to transformation.

RESULTS

In this study, the physiological consequences of rolB oncogene incorporation into the DNA of Dionaea muscipula J. Ellis was evaluated at the level of primary and secondary metabolism. Examination of the teratoma (transformed shoots) cultures of two different clones (K and L) showed two different strategies for dealing with the presence of the rolB gene. Clone K showed an increased ratio of free fatty acids to lipids, superoxide dismutase activity, synthesis of the oxidised form of glutathione, and total pool of glutathione and carotenoids, in comparison to non-transformed plants (control). Clone L was characterised by increased accumulation of malondialdehyde, proline, activity of superoxide dismutase and catalase, total pool of glutathione, ratio of reduced form of glutathione to oxidised form, and accumulation of selected phenolic acids. Moreover, clone L had an enhanced ratio of total triglycerides to lipids and accumulated saccharose, fructose, glucose, and tyrosine.

CONCLUSIONS

This study showed that plant transformation with the rolB oncogene derived from R. rhizogenes induces a pleiotropic effect in plant tissue after transformation. Examination of D. muscipula plant in the context of transformation with wild strains of R. rhizogenes can be a new source of knowledge about primary and secondary metabolites in transgenic organisms.

Methyl jasmonate enhances ursolic, oleanolic and rosmarinic acid production and sucrose induced biomass accumulation, in hairy roots of Lepechinia caulescens

Background

Ursolic (UA), oleanolic (OA) and rosmarinic (RA) acids are bioactive metabolites found in Lepechinia caulescens that have generated interest for their health benefits, which include antimicrobial, antioxidant, antimutagenic, gastroprotective, antidiabetic, antihypertensive and anti-inflammatory properties, among others. To date, very few attempts have been made to evaluate the potential for simultaneous production of these bioactive compounds, using a biotechnological approach. Hairy root cultures offer a biotechnology approach that can be used to study the factors affecting the biosynthesis and the production of UA, OA and RA. In the current study, we established hairy root cultures of L. caulescens and evaluated the effect of sucrose on biomass accumulation, and the effect of different concentrations and times of exposure of methyl jasmonate (MeJA), on the accumulation of UA, OA and RA.

Methods

Leaves from plants of L. caulescens were inoculated with Agrobacterium rhizogenes strain ATCC 15834. PCR of rolB gene confirmed the transgenic nature of hairy roots. Hairy roots were subcultured in semisolid MSB5 medium, supplemented with 15, 30, 45 or 60 g/L sucrose and after 4 weeks, dry weight was determined. The accumulation of UA, OA and RA of wild plants and hairy roots were determined by HPLC. Finally, the hairy roots were treated with 0, 100, 200 and 300 µM of MeJA and the content of bioactive compounds was analyzed, after 24, 48 and 72 h.

Results

High frequency transformation (75%) was achieved, using leaf explants from axenic seedlings, infected with A. rhizogenes. The hairy roots showed an enhanced linear biomass accumulation, in response to the increase in sucrose concentration. The hairy root cultures in MSB5 medium, supplemented with 45 g/L sucrose, were capable to synthesizing UA (0.29 ± 0.00 mg/g DW), OA (0.57 ± 0.00 mg/g DW) and RA (41.66 ± 0.31 mg/g DW), about two, seven and three times more, respectively, than in roots from wild plants. Elicitation time and concentration of MeJA resulted in significant enhancement in the production of UA, OA and RA, with treatments elicited for 24 h, with a concentration of 300 µM of MeJA, exhibiting greatest accumulation.

Conclusion

This is the first report on development of hairy root cultures of L. caulescens. Future studies should aim towards further improving triterpenes and polyphenolic compound production in hairy roots of L. caulescens, for use in the pharmaceutical and biotechnological industry.

‘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.