Agrobacterium rhizogenes mediated transformation of Scutellaria baicalensis and production of flavonoids in hairy roots

Using different explants of in vitro seed grown Scutellaria baicalensis Georgi plantlets, hairy roots were induced following inoculation of Agrobacterium rhizogenes strains A4GUS, R1000 LBA 9402 and ATCC11325. The A4GUS proved to be more competent than other strains and the highest transformation rates were observed in cotyledonary leaf explant (42.6%). The transformed roots appeared after 15-20 d of incubation on hormone free Murashige and Skoog medium. Growth of hairy roots was assessed on the basis of total root elongation, lateral root density and biomass accumulation. Maximum growth rate was recorded in root:medium ratio 1:100 (m/v). Hairy root lines were further established in Gamborg B5 medium and the biomass increase was maximum from 15 to 30 d. PCR, Southern hybridization and RT-PCR confirmed integration and expression of left and right termini-linked Ri T-DNA fragment of the Ri plasmid from A4GUS into the genome of Scutellaria baicalensis hairy roots. GUS assay was also performed for further integration and expression. All the clones showed higher growth rate than non-transformed root and accumulated considerable amounts of the root-specific flavonoids. Baicalin content was 14.1-30.0% of dry root mass which was significantly higher than in control field-grown roots (18%). The wogonin content varied from 0.08 to 0.18% among the hairy root clones which was also higher than in non-transformed roots (0.07%).