[Enhanced biosynthesis of scopolamine in transgenic Atropa belladonna by overexpression of h6h gene].

Transgenic Atropa belladonna with high levels of scopolamine was developed by metabolic engineering. A functional gene involved in the rate limiting enzyme of h6h involved in the biosynthetic pathway of scopolamine was over expressed in A. belladonna via Agrobacterium-mediation. The transgenic plants were culturing till fruiting through micropropogating and acclimating. The integration of the h6h genes into the genomic DNA of transgenic plants were confirmed by genomic polymerase chain reaction (PCR) analysis. Analysis of the difference of plant height, crown width, stem diameter, leaf length, leaf width, branch number and fresh weight was carried out using SPSS software. The content of hyoscyamine and scopolamine in roots, stems, leaves and fruits was determined by HPLC. The investigation of the expression levels of Hnh6h by qPCR. Both Kan(r) and Hnh6h genes were detected in five transgenic lines of A. belladonna plants (A8, A11, A12, C8 and C19), but were not detected in the controls. The plant height, crown width, stem diameter, leaf length, leaf width, branch number and fresh weight of transgenic plants did not decrease by comparison with the non-transgenic ones, and furthermore some agronomic characters of transgenic plants were better than those of the controls. The highest level of scopolamine was found in leaves of transgenic A. belladonna, and the content of scopolamine was also higher than that of hyoscyamine in leaves. The contents of scopolamine of leaves in different transgenic lines were listed in order: C8 > A12 > C19 > A11 > A8, especially, the content of scopolamine in transgenic line C8 was 2.17 mg x g(-1) DW that was 4.2 folds of the non-transgenic ones (0.42 mg x g(-1) DW). The expression of transgenic Hnh6h was detected in all the transgenic plants but not in the control. The highest level of Hnh6h expression was found in transgenic leaves. Overexpression of Hnh6h is able to break the rate limiting steps involved in the downstream pathway of scopolamine biosynthesis, and thus promotes the metabolic flux flowing toward biosynthesis of scopolamine to improve the capacity of scopolamine biosynthesis in transgenic plants. As a result, transgenic plants of A. belladonna with higher level of scopolamine were developed.