Metabolic engineering of plant L-ascorbic acid biosynthesis: recent trends and applications.

Vitamin C (L-ascorbic acid; AsA) is the major soluble antioxidant found in plants and is also an essential component of human nutrition. Although numerous biotechnological methods have been exploited to increase its yield, pressures such as commercial competition and environmental concerns make it urgent to find a new way for industrial production of plant-derived AsA. Engineering plant AsA has now become feasible because of our increased understanding of its biosynthetic pathway. Several possible strategies could be followed to increase AsA production, such as overcoming the rate limiting steps in the biosynthetic pathway, promoting recycling, and reducing catabolism. For these purposes, genes of plant, microbial and animal origins have been successfully used. Several examples will be given to illustrate these various approaches. The existing and potential achievements in increasing AsA production would provide the opportunity for enhancing nutritional quality and stress tolerance of crop plants.