title: Reduction of cholesterol and glycoalkaloid levels in transgenic potato plants by overexpression of a type 1 sterol methyltransferase cDNA.
abstract: Transgenic potato (Solanum tuberosum cv Désirée) plants overexpressing a soybean (Glycine max) type 1 sterol methyltransferase (GmSMT1) cDNA were generated and used to study sterol biosynthesis in relation to the production of toxic glycoalkaloids. Transgenic plants displayed an increased total sterol level in both leaves and tubers, mainly due to increased levels of the 24-ethyl sterols isofucosterol and sitosterol. The higher total sterol level was due to increases in both free and esterified sterols. However, the level of free cholesterol, a nonalkylated sterol, was decreased. Associated with this was a decreased glycoalkaloid level in leaves and tubers, down to 41% and 63% of wild-type levels, respectively. The results show that glycoalkaloid biosynthesis can be down-regulated in transgenic potato plants by reducing the content of free nonalkylated sterols, and they support the view of cholesterol as a precursor in glycoalkaloid biosynthesis.
authors.affiliation: Department of Plant Biology and Forest Genetics, Swedish University of Agricultural Sciences, 75007 Uppsala, Sweden.
authors.forename: Lisa
authors.initials: L
authors.lastname: Arnqvist
authors.forename: Paresh C
authors.initials: PC
authors.lastname: Dutta
authors.forename: Lisbeth
authors.initials: L
authors.lastname: Jonsson
authors.forename: Folke
authors.initials: F
authors.lastname: Sitbon
mesh_terms: D000470:Alkaloids / Q000096:biosynthesis / Q000378:metabolism*; D002784:Cholesterol / Q000096:biosynthesis / Q000378:metabolism*; D018076:DNA, Complementary / Q000235:genetics; D015870:Gene Expression; D008780:Methyltransferases / Q000235:genetics* / Q000378:metabolism*; D015394:Molecular Structure; D018515:Plant Leaves / Q000378:metabolism; D035281:Plant Tubers / Q000378:metabolism; D030821:Plants, Genetically Modified; D011198:Solanum tuberosum / Q000201:enzymology* / Q000235:genetics*; D013025:Glycine max / Q000235:genetics
chemical_list: D000470:Alkaloids; D018076:DNA, Complementary; D002784:Cholesterol; D008780:Methyltransferases