UNIVERSITY PARK, Penn.—Scientists have identified a gene in rice that controls the size and weight of rice grains, which may help breed high-yield rice. "The GIF1 gene is responsible for controlling the activity of the enzyme invertase, which is located in the cell wall and converts sucrose to substances that then are used to create starch," said study researcher Zuhua He. "Invertase is important in the formation of starch within developing grains of rice. If invertase is not active, the rice plant cannot produce edible grains."