Elevating the vitamin E content of plants through metabolic engineering.
alpha-Tocopherol (vitamin E) is a lipid-soluble antioxidant synthesized only by photosynthetic organisms. alpha-Tocopherol is an essential component of mammalian diets, and intakes in excess of the U.S. recommended daily allowance are correlated with decreased incidence of a number of degenerative human diseases. Plant oils, the main dietary source of tocopherols, typically contain alpha-tocopherol as a minor component and high levels of its biosynthetic precursor, gamma-tocopherol. A genomics-based approach was used to clone the final enzyme in alpha-tocopherol synthesis, gamma-tocopherol methyltransferase. Overexpression of gamma-tocopherol methyltransferase in Arabidopsis seeds shifted oil compositions in favor of alpha-tocopherol. Similar increases in agricultural oil crops would increase vitamin E levels in the average U.S. diet.
Shintani
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Department of Biochemistry, Mail Stop 200, University of Nevada, Reno, NV 89557, USA.
DellaPenna
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D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D000458:Cyanobacteria / Q000235:genetics; D015870:Gene Expression; D005798:Genes, Bacterial; D017343:Genes, Plant; D005818:Genetic Engineering; D008780:Methyltransferases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009876:Operon; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012639:Seeds / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D013379:Substrate Specificity; D014170:Transformation, Genetic; D014810:Vitamin E / Q000032:analysis / Q000096:biosynthesis*
D011994:Recombinant Proteins; D014810:Vitamin E; D008780:Methyltransferases; C047259:gamma-tocopherol methyltransferase