Scientists find rice gene that's linked to yields

Monday, April 14, 2003

Chinese scientists have discovered a gene that regulates the branching and height of rice plants, hinting at a way to boost yields of a crop that feeds more than half the world's population.

The researchers showed that inserting extra copies of the gene into rice plants increased the number of seed-bearing sprouts called tillers, although they did not grow those plants to harvest.

A team led by Jiayang Li, director of the Chinese Academy of Sciences' Institute of Genetics in Beijing, report the discovery in journal Nature.

Other scientists said the gene is clearly important but likely represents just one part of the biological machinery that regulates yield.

"This is not what I would call a yield gene. It affects plant architecture and plant architecture ultimately affects yield," said Susan McCouch, a professor of and plant biology at Cornell University.

"It's not an immediate fix ... but it's still really significant."

McCouch, who was not involved in the research, said the gene appears to be a "master switch" that regulates proteins that control a number of features of rice

Li agrees that discovering the gene is just a first step toward understanding the complex factors that influence a plant's yield.

His team began their work by scrutinizing a naturally occurring mutant rice plant that grows into a single main stem, without the grain-bearing tillers that normal rice plants sprout.

Aided by a draft map of the rice plant's genome completed last year by an international team of scientists, they determined that a single defective copy of the MOC1 gene impaired the plant's growth.

They inserted one and three normal versions of the gene into the mutant plants and found that all developed into normal-appearing rice plants, although the plants with three copies produced many more tillers than the ones harboring a single copy.

The altered plants were also shorter -- a helpful trait for farming.

Although those plants were not grown to harvest to assess their yields, in theory because they produced more tillers that could mean more grains of rice.

Li said his team is now working to see if simply adding extra, normal copies of MOC1 can increase the yield of normal rice plants. "We hope we can have some fruitful results in the future," he said.

However, Li said simply adding several extra copies of the gene to normal plants could instead decrease yields. That is because plants with too many tiller tend to develop smaller "ears" of rice, which grow from specialized branches that grow on the tillers.

Pamela Ronald, a professor of plant pathology at the University of California in Davis, said Li's work is intriguing even if it is just a first step toward boosting yields.

She said now that scientists have the rice plant's genome at their disposal their work to improve rice's drought-tolerance, disease-resistance and boost yields will become easier. "This is just the first of many exciting discoveries to come," she said.

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