Scientists identify gene that may contribute to improved ...( A team of scientists including Penn...)

A team of scientists, including Penn State Distinguished Professor of Biology Hong Ma, has identified a gene in rice that controls the size and weight of rice grains. The gene may prove to be useful for breeding high-yield rice and, thus, may benefit the vast number of people who rely on this staple food for survival. "Our work shows that it is possible to increase rice's yield by enhancing the expression of a particular gene," said Ma. The team's results will be published on 28 September 2008 in an early online edition of the journal Nature Genetics, and in the November print issue of the journal.

The researchers first searched for and identified mutant strains of rice that exhibited underweight grains. "We found a particular mutant that is defective in its ability to produce normal-sized grains," said Zuhua He, a biology professor at the Chinese Academy of Sciences and the leader of the team. The group then examined the mutant and found that it carried a mutation within the GIF1 gene. "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 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."

Next, to test the ability of the GIF1 gene to control the production of invertase, the team measured the activity of invertase within a normal strain of rice, in which the GIF1 gene lacked any mutations, and within a mutant strain of rice, in which the GIF1 gene contained a mutation that caused a defect in the invertase activity. 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 ri
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