title: Overexpression of tropinone reductases alters alkaloid composition in Atropa belladonna root cultures.
abstract: The medicinally applied tropane alkaloids hyoscyamine and scopolamine are produced in Atropa belladonna L. and in a small number of other Solanaceae. Calystegines are nortropane alkaloids that derive from a branching point in the tropane alkaloid biosynthetic pathway. In A. belladonna root cultures, calystegine molar concentration is 2-fold higher than that of hyoscyamine and scopolamine. In this study, two tropinone reductases forming a branching point in the tropane alkaloid biosynthesis were overexpressed in A. belladonna. Root culture lines with strong overexpression of the transcripts contained more enzyme activity of the respective reductase and enhanced enzyme products, tropine or pseudotropine. High pseudotropine led to an increased accumulation of calystegines in the roots. Strong expression of the tropine-forming reductase was accompanied by 3-fold more hyoscyamine and 5-fold more scopolamine compared with control roots, and calystegine levels were decreased by 30-90% of control. In some of the transformed root cultures, an increase of total tropane alkaloids was observed. Thus, transformation with cDNA of tropinone reductases successfully altered the ratio of tropine-derived alkaloids versus pseudotropine-derived alkaloids.
authors.affiliation: Institute of Pharmaceutical Biology, Martin-Luther-University Halle-Wittenberg, Hoher Weg 8, D-06120 Halle/Saale, Germany.
authors.forename: Ute
authors.initials: U
authors.lastname: Richter
authors.forename: Grit
authors.initials: G
authors.lastname: Rothe
authors.forename: Anne-Katrin
authors.initials: AK
authors.lastname: Fabian
authors.forename: Bettina
authors.initials: B
authors.lastname: Rahfeld
authors.forename: Birgit
authors.initials: B
authors.lastname: Dräger
mesh_terms: D000429:Alcohol Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D000470:Alkaloids / Q000096:biosynthesis* / Q000737:chemistry; D001532:Atropa belladonna / Q000201:enzymology*; D015870:Gene Expression; D015394:Molecular Structure; D018517:Plant Roots / Q000201:enzymology; D030821:Plants, Genetically Modified
chemical_list: D000470:Alkaloids; D000429:Alcohol Oxidoreductases; C083753:tropinone reductase