Chromium-induced tropane alkaloid production and H6H gene expression in Atropa belladonna L. (Solanaceae) in vitro-propagated plantlets

Hyoscyamine and scopolamine tropane alkaloids found in several solanaceous plants are anticholinergic drugs. Hyoscyamine 6 beta-hydroxylase (H6H) catalyzes two consecutive oxidation reactions. The first reaction is the hydroxylation of hyoscyamine to 6 beta-hydroxyhyoscyamine and the second is epoxidation of 6 beta-hydroxyhyoscyamine yielding scopolamine that is the final metabolite in the tropane alkaloid biosynthetic pathway. The effects of trivalent chromium as KCr (SO4)(2) on the production of tropane alkaloids and the expression of hyoscyamine 6 beta-hydroxylase gene (h6h) were studied in micro-propagated Atropa belladonna L. plantlets. The results showed that chromium treatment decreased the growth parameters (weights and lengths of the plantlets) and chlorophyll contents and increased proline contents. Moreover, semiquantitave RT-PCR analysis showed that the transcript level of H6H increased under chromium treatment. This treatment also increased hyoscyamine and scopolamine contents as shown by HPLC analysis. Changes of scopolamine contents correlate with the expression levels of h6h gene under different concentrations of chromium. (C) 2011 Elsevier Masson SAS. All rights reserved.