Nature Biotechnology
21, 1082 - 1087 (2003)
Published online: 3 August 2003; | doi:10.1038/nbt853
Metabolic redesign of vitamin E biosynthesis in plants for tocotrienol
production and increased antioxidant contentEdgar B Cahoon1, 2, Sarah E Hall1, Kevin G Ripp1, Thaya S Ganzke1, William D Hitz1
& Sean J Coughlan1, 21
Crop Genetics Research and Development, Pioneer
Hi-Bred, A DuPont Company, Experimental Station, Wilmington,
Delaware 19880, USA. 2
Present addresses: USDA−ARS Plant Genetics
Research Unit, Donald Danforth Plant Science Center, 975 North
Warson Road, Saint Louis, Missouri
63132, USA (E.B.C.), Agilent Technologies,
Inc., Little Falls Site, 2850 Centerville Road,
Wilmington, Delaware 19808-1644, USA
(S.J.C.).
Correspondence should be addressed to Edgar B Cahoon ecahoon@danforthcenter.orgTocotrienols 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.
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