Metabolic engineering of an alternative pathway for ascorbic acid biosynthesis in plants

Plants and most animals can synthesize their own L-ascorbic acid (vitamin C), but a mutation in the L-gulono--lactone oxidase gene in the primate lineage makes it necessary for humans to acquire this vital compound from their diet. Despite the fact that plants and animals synthesize ascorbic acid via different pathways, transgenic tobacco and lettuce plants expressing a rat cDNA encoding L-gulono--lactone oxidase accumulated up to seven times more ascorbic acid than untransformed plants. These results demonstrate that basal levels of ascorbic acid in plants can be significantly increased by expressing a single gene from the animal pathway.