The term Vitamin E can apply to eight naturally occurring forms of compounds known as tocotrienols and tocopherols. The synthesis of the former in plants is well studied. In the new work, Edgar B. Cahoon of the USDA-ARS Plant Genetics Research Unit and his colleagues investigated the pathway that leads to tocopherols. The researchers isolated genes that encode enzymes known as homogentisic acid geranylgeranyl transferases (HGGT). Plants engineered to overexpress HGGT contained 10 to 15 times the total Vitamin E content as normal plants did. In corn seeds, the increase was sixfold. The authors write in the September issue of the journal Nature Biotechnology that their results "demonstrate the ability to enhance the antioxidant content of crops by introduction of an enzyme that redirects metabolic flux."
Further work is required to maximize the dietary benefits of Vitamin E-rich plants produced using this method, the authors note. But if the process can be refined, there could be additional advantages. For one, the plants will most likely be more resistant to oxidative stresses, leading to seeds that can be stored longer and improved crop productivity. In addition, vegetable oils manufactured from the seeds would have an extended shelf life.