Hairy root culture of Artemisia annua L. by Ri plasmid transformation and biosynthesis of artemisinin.

The hairy root culture system of the medical plant Artemisia annua L. was established by infection with Agrobacterium rhizogenes R1601. The transgenic state of transformed roots was confirmed by Southern blot hybridization with TL-DNA of pFw302. The expression of NPTII gene was confirmed by enzymic assay. The important secondary metabolites-artemisinin was obtained in the hairy root culture. The effects of various physical and chemical factors on the growth of the hairy roots and production of artemisinin were studied. Artemisinin could be detected in hairy roots cultures in the light. The optimum pH value of the medium was 5.4. Fast growth of the hairy roots and maximal production of artemisinin was observed in the presence of 3% sucrose. Low concentration of naphthylacetic acid (0.025 mg/L) enhanced the growth of the roots but inhibited the production of artemisinin. The growth and artemisinin production in hairy root cultures were greatly promoted by the addition of gibberellin (GA3) to the medium. Its optimum concentration was 4.8 mg/L.