Hairy roots induced by Agrobacterium rhizogenes and production of regenerative plants in hairy root cultures in maize

Production of Phenolic Compounds and Antioxidant Activity in Hairy Root Cultures of Salvia plebeia

Salvia plebeia (Lamiaceae) is a medicinal plant containing diverse bioactive constituents that have biological properties. In this study, we determined the optimal conditions (media and auxin) for the hairy root culture of S. plebeia for the growth and accumulation of phenolic compounds and evaluated its antioxidant activities. Rosmarinic acid and five phenylpropanoids were detected using high-performance liquid chromatography. The hairy roots grown in 1/2 SH medium with 1 mg/L NAA had a high level of rosmarinic acid content. Hairy roots cultured in 1 mg/L NAA had the highest total content of five phenylpropanoids. Compared to wild-type roots grown in the field, hairy roots (NAA 1) expressed similar levels of rosmarinic acid but significantly enhanced phenylpropanoid accumulation. Furthermore, the total phenolic content and total flavonoid content of hairy roots (NAA 1) were 2.22 and 1.73 times higher than those of wild-type roots. In the results of DPPH, ABTS, and reducing power assays, the hairy roots (NAA 1) showed higher free radical scavenging effects and reduction potential than the wild-type roots. These results suggest that S. plebeia hairy roots cultured under optimal conditions, which exhibit enhanced phenolic compound accumulation and antioxidant activity, can potentially be used as sources of antioxidants.

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.

Hairy root induction and Farnesiferol B production of endemic medicinal plant Ferula pseudalliacea

The effects of medium, gibberellic acid (GA₃) and stratification treatments on the seed germination of Ferula pseudalliacea were evaluated. Filter paper medium, 500 micro molar GA₃ and 8 week chilling treatment were resulted in significantly more seed germination than others. F. pseudalliacea was also transformed by Agrobacterium rhizogenes. Explants from young leaves, stems, cotyledon, and embryo were inoculated with A. rhizogenes strains ATCC 15834, 1724, A4, LB9402 and Ar318. Hairy roots were induced only from 10 to 12-days embryo explants using strains ATCC 15824 and 1724. Although, the transformation efficiency of ATCC 15834 (4%) strain was higher than 1724 (2%). Maximum hairy root transformation frequency (25%) was obtained in infection time of 10 min compared to that of 20 (20%) and 30 (5%) min. In addition, the transformation rate was significantly higher at the inoculation time of 72 h (29%) compared to that of 48 h (22%) and 24 h (6%). Transgenic hairy root lines were confirmed by PCR amplification of rolB gene. Hairy root lines were produced higher biomass in half B5 medium compared to that of half MS medium. Hairy roots lines from the strain ATCC 15834 produced more hairy root numbers and fresh and dried biomass compared to that of the strain 1724. Analyses of transgenic hairy root and natural roots extracts using HPLC showed that all the hairy root lines produced farnesiferol B.

Striga parasitizes transgenic hairy roots of Zea mays and provides a tool for studying plant-plant interactions

BACKGROUND

Striga species are noxious root hemi-parasitic weeds that debilitate cereal production in sub-Saharan Africa (SSA). Control options for Striga are limited and developing Striga resistant crop germplasm is regarded as the best and most sustainable control measure. Efforts to improve germplasm for Striga resistance by a non-Genetic Modification (GM) approach, for example by exploiting natural resistance, or by a GM approach are constrained by limited information on the biological processes underpinning host-parasite associations. Additionaly, a GM approach is stymied by lack of availability of candidate resistance genes for introduction into hosts and robust transformation methods to validate gene functions. Indeed, a majority of Striga hosts, the world's most cultivated cereals, are recalcitrant to genetic transformation. In maize, the existing protocols for transformation and regeneration are tedious, lengthy, and highly genotype-specific with low efficiency of transformation.

RESULTS

We used Agrobacterium rhizogenes strain K599 carrying a reporter gene construct, Green Fluorescent Protein (GFP), to generate transgenic composite maize plants that were challenged with the parasitic plant Striga hermonthica. Eighty five percent of maize plants produced transgenic hairy roots expressing GFP. Consistent with most hairy roots produced in other species, transformed maize roots exhibited a hairy root phenotype, the hallmark of A. rhizogenes mediated transformation. Transgenic hairy roots resulting from A. rhizogenes transformation were readily infected by S. hermonthica. There were no significant differences in the number and size of S. hermonthica individuals recovered from either transgenic or wild type roots.

CONCLUSIONS

This rapid, high throughput, transformation technique will advance our understanding of gene function in parasitic plant-host interactions.