A gene in rice that controls the size and weight of rice grains has been identified, and may thus be useful for breeding 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. 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."

The scientists found that invertase activity in the mutant strain was only 17 percent of the activity that was observed in the normal strain, suggesting that the GIF1 gene does, indeed, control invertase activity. The team then created transgenic lines of rice in which the GIF1 gene is overexpressed and found that, compared with normal strains, the transgenic rice had larger and heavier grains.

Photo: The researchers created transgenic lines of rice (G-2 and G-8) in which the GIF1 gene was overexpressed. Compared to the normal strain (WT), they found that the transgenic rice had larger and heavier grains. In this figure, the grains on the top are encased in their shells and the grains on the bottom have had their shells removed. Credit: Zuhua He, Chinese Academy of Sciences

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