Improving Photosynthesis by Gene Engineering
William L. Ogren
In photosynthesis, a plant uses sunlight to remove carbon dioxide from the atmosphere and converts it into sugar and starch. The plant uses these for growth of seeds, fruits, tubers, or other plant parts of economic value, such as leaves, roots, and stems. Because crop productivity increases when photosynthesis occurs more rapidly, much research is directed toward improving this process.
One approach being taken by a USDA research team at the University of Illinois Department of Agronomy is to speed up the first step of photosynthesis. Five years ago, this team discovered an enzyme that governs the rate at which leaves absorb carbon dioxide. The gene that determines the structure of this enzyme, and thus the enzyme's activity, was then obtained. Using genetic engineering, several different changes were made in the gene to alter the properties of its enzyme product.
It cannot be predicted how changes in enzymes will affect their activity. Because enzymes have highly organized structures, changes usually result in less activity. In this case, however, one of the altered enzymes had more activity than normal. Attempts are now being made to incorporate the modified genes into plants, using standard methods of genetic transformation. Following transformation, photosynthesis measurements of the transgenic plants will be made. Such tests will determine the possibility of improved plant productivity by modifying this component of photosynthesis.
William L. Ogren, research leader, USDA/ARS, and professor of agronomy