Metabolic Engineering of Plant Vitamin C Biosynthesis for Improved Nutrition and Health

This project is aimed at uncovering the biosynthesis of L-ascorbic acid (vitamin C) in plants and to engineer plants to contain higher levels of this important molecule.

This is a collaborative project with the groups of Craig Nessler and Boris Chevone at the Department of Plant Pathology, Physiology & Weed Science. Funding is from the NSF and USDA under the Interagency Agreement on Metabolic Engineering.

Background

The biosynthesis of ascorbic acid in plants has remained unknown for a large number of years, while its animal equivalent was established in the 1950s. Recently, Wheeler et al. (1998) proposed a pathway that is consistent with experiments where labeled glucose is transformed into ascorbic acid without inversion of the carbon chain. While there is now strong supporting evidence for this pathway, there are also results that indicate that ascorbic acid may also be synthesized in different ways:

• a series of precursors that are not intermediates in the Wheeler pathway lead to ascorbic acid (Davey et al., 1999)
• expression of the terminal enzyme of the animal pathway (GLO) in plants leads to increased ascorbic acid levels (Jain & Nessler, 2000), implying that the animal precursor L-gulono-1,4-lactone is present in plants

We are investigating what these other pathways may be and devise ways in which plants can be made to increase their vitamin C content.

Links

• Project pages (only for members)