Enhancement of scopolamine production in Hyoscyamus muticus L. hairy root cultures by genetic engineering

In order to test the possibility of enhancing the production of pharmaceuti cally valuable scopolamine in transgenic cultures, the 35S-h6h transgene th at codes for the enzyme hyoscyamine-6 beta-hydrosylase (EC 1.14.11.11) was introduced into Hyoscyamus muticus L. strain Cairo (Egyptian henbane). This plant was chosen for its capability to produce very high amounts of tropan e alkaloids (up to 6% of the dry weight in the leaves of mature plant). To our knowledge, this is the first time such a large population of transgenic cultures has been studied at the morphological, chemical and genetic level s. A great variation was observed in the tropane alkaloid production among the 43 positive transformants. The best clone (KB7) produced 17 mg/l scopol amine, which is over 100 times more than the control clones. However, conve rsion of hyoscyamine to scopolamine was still incomplete. The expression of h6h was found to be proportional to the scopolamine production, and was th e main reason behind the variation in the scopolamine/hyoscyamine ratio in the hairy-root clones. These results indicate that H. muticus strain Cairo has a potential for even more enhanced scopolamine production with more eff icient gene-expression systems.