title: Metabolic redesign of vitamin E biosynthesis in plants for tocotrienol production and increased antioxidant content.
abstract: Tocotrienols are the primary form of vitamin E in seeds of most monocot plants, including cereals such as rice and wheat. As potent antioxidants, tocotrienols contribute to the nutritive value of cereal grains in human and livestock diets. cDNAs encoding homogentisic acid geranylgeranyl transferase (HGGT), which catalyzes the committed step of tocotrienol biosynthesis, were isolated from barley, wheat and rice seeds. Transgenic expression of the barley HGGT in Arabidopsis thaliana leaves resulted in accumulation of tocotrienols, which were absent from leaves of nontransformed plants, and a 10- to 15-fold increase in total vitamin E antioxidants (tocotrienols plus tocopherols). Overexpression of the barley HGGT in corn seeds resulted in an increase in tocotrienol and tocopherol content of as much as six-fold. These results provide insight into the genetic basis for tocotrienol biosynthesis in plants and demonstrate the ability to enhance the antioxidant content of crops by introduction of an enzyme that redirects metabolic flux.
authors.affiliation: Crop Genetics Research and Development, Pioneer Hi-Bred, A DuPont Company, Experimental Station, Wilmington, Delaware 19880, USA. ecahoon@danforthcenter.org
authors.forename: Edgar B
authors.initials: EB
authors.lastname: Cahoon
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Hall
authors.forename: Kevin G
authors.initials: KG
authors.lastname: Ripp
authors.forename: Thaya S
authors.initials: TS
authors.lastname: Ganzke
authors.forename: William D
authors.initials: WD
authors.lastname: Hitz
authors.forename: Sean J
authors.initials: SJ
authors.lastname: Coughlan
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000235:genetics* / Q000378:metabolism*; D000975:Antioxidants / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D005818:Genetic Engineering / Q000379:methods*; D001467:Hordeum / Q000201:enzymology / Q000235:genetics; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism; D012275:Oryza / Q000201:enzymology / Q000235:genetics; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000378:metabolism*; D015202:Protein Engineering / Q000379:methods*; D011994:Recombinant Proteins / Q000378:metabolism; D024505:Tocopherols / Q000378:metabolism; D024508:Tocotrienols / Q000378:metabolism; D014908:Triticum / Q000201:enzymology / Q000235:genetics; D014810:Vitamin E / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D000975:Antioxidants; D009097:Multienzyme Complexes; D011994:Recombinant Proteins; D024508:Tocotrienols; D014810:Vitamin E; D019883:Alkyl and Aryl Transferases; C083291:geranylgeranyltransferase type-I; D024505:Tocopherols