title: Increased alpha-tocopherol content in soybean seed overexpressing the Perilla frutescens gamma-tocopherol methyltransferase gene.
abstract: Tocopherols, with antioxidant properties, are synthesized by photosynthetic organisms and play important roles in human and animal nutrition. In soybean, gamma-tocopherol, the biosynthetic precursor to alpha-tocopherol, is the predominant form found in the seed, whereas alpha-tocopherol is the most bioactive component. This suggests that the final step of the alpha-tocopherol biosynthetic pathway catalyzed by gamma-tocopherol methyltransferase (gamma-TMT) is limiting in soybean seed. Soybean oil is the major edible vegetable oil consumed, so manipulating the tocopherol biosynthetic pathway in soybean seed to convert tocopherols into more active alpha-tocopherol form could have significant health benefits. In order to increase the soybean seed alpha-tocopherol content, the gamma-TMT gene isolated from Perilla frutescens was overexpressed in soybean using a seed-specific promoter. One transgenic plant was recovered and the progeny was analyzed for two generations. Our results demonstrated that the seed-specific expression of the P. frutescens gamma-TMT gene resulted in a 10.4-fold increase in the alpha-tocopherol content and a 14.9-fold increase in the beta-tocopherol content in T2 seed. Given the relative contributions of different tocopherols to vitamin E activity, the activity in T2 seed was calculated to be 4.8-fold higher than in wild-type seed. In addition, the data obtained on lipid peroxidation indicates that alpha-tocopherol may have a role in preventing oxidative damage to lipid components during seed storage and seed germination. The increase in the alpha-tocopherol content in the soybean seed could have a potential to significantly increase the dietary intake of vitamin E.
authors.affiliation: Department of Plant and Soil Sciences, University of Kentucky, 1405 Veterans Road, Lexington, KY 40546-0312, USA.
authors.forename: Venkata S
authors.initials: VS
authors.lastname: Tavva
authors.forename: Yul-Ho
authors.initials: YH
authors.lastname: Kim
authors.forename: Isabelle A
authors.initials: IA
authors.lastname: Kagan
authors.forename: Randy D
authors.initials: RD
authors.lastname: Dinkins
authors.forename: Kyung-Hwan
authors.initials: KH
authors.lastname: Kim
authors.forename: Glenn B
authors.initials: GB
authors.lastname: Collins
mesh_terms: D000595:Amino Acid Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D002851:Chromatography, High Pressure Liquid; D018506:Gene Expression Regulation, Plant; D015227:Lipid Peroxidation; D008315:Malondialdehyde / Q000378:metabolism; D008780:Methyltransferases / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D015394:Molecular Structure; D031344:Perilla frutescens / Q000201:enzymology* / Q000235:genetics; D030821:Plants, Genetically Modified; D012639:Seeds / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment; D013025:Glycine max / Q000235:genetics* / Q000378:metabolism; D014810:Vitamin E / Q000378:metabolism; D024502:alpha-Tocopherol / Q000737:chemistry / Q000378:metabolism*
chemical_list: D014810:Vitamin E; D008315:Malondialdehyde; D008780:Methyltransferases; C047259:gamma-tocopherol methyltransferase; D024502:alpha-Tocopherol