Establishment of transformed root cultures of Paulownia tomentosa for verbascoside production

Abstract

The formation of eleven hairy root lines of Paulownia tomentosa was induced by infection of stem segments with strains of Agrobacterium rhizogenes LBA 9402 and A4. The transformation frequency was dependent on the age of expiant. Hairy root cultures grew rapidly with the characteristic high degree of lateral branching in hormone-free Woody Plant liquid medium. Production of verbascoside in hairy roots under culture conditions was demonstrated. Depending on the hairy root line used, the level of verbascoside varied from 1.7 to 8% of dry weight. Enhancement of verbascoside production was attempted by using various basal media, like Murashige and Skoog (MS), Gamborg (B5) and Woody Plant (WP) as well as half-strength MS, B5 and WP media. Experiments with one of the most productive line (PT-3) showed that the maximum verbascoside yield was achieved in half-strength Gamborg's B5 liquid medium. Under these conditions the transformed roots had a verbascoside content amounting to 9.5% of dry weight (more than 1 g/L of culture). The amount was approximately doubled compared with the yield in the roots of 4.5-month-old-plants.