Rice gene code fully mapped, promising better crops

August 11, 2005|By Robert Lee Hotz | Robert Lee Hotz,LOS ANGELES TIMES

Researchers have deciphered the complete genetic code of rice, accelerating efforts to improve a staple that feeds half the world, an international consortium led by Japan announced yesterday.

Humanity has been growing rice for 10,000 years but only now have scientists dissected the molecules of its creation so the farmers who raise 880 billion pounds of rice a year can directly manipulate the blueprint of its growth and development.

There are 120,000 varieties of rice, but just two of them - japonica and indica - supply 20 percent of the world's calories, feeding more than 2 billion people in Asia alone. Demand has doubled in the past 20 years. By 2025, as many as 4.6 billion people will depend on rice for survival, experts predict.

Plant breeders have used preliminary information from the rice genome to craft experimental strains of rice that better withstand extremes of wind and cold.

"It is catalyzing a lot of research," said one of the project's leaders, Richard McCombie at the Cold Spring Harbor Laboratory in New York. "There is a lot of pressure on breeders to improve the crop, and this is a valuable tool to do that."

All told, it took researchers at 32 centers in 10 countries eight years to completely document and map the spiral chain of amino acids that encodes the life cycle of the rice plant.

Rough drafts of the japonica and indica genomes, developed by a San Diego-based research group and a research consortium in China, were released in 2002.

In research to be published today in the journal Nature, they reported that nature takes only two-thirds as many genes as scientists once predicted to create a rice plant but, even so, thousands more than required to make a human being.

The japonica strain of rice, researchers discovered, contains 37,544 genes spelled out in 389 million chemical letters of DNA packaged in 12 chromosomes, compared with about 20,000 known genes in the 24 chromosomes of the human genome.

More than 2,800 genes appear to be unique to rice, the scientists said.

At a time when researchers are quick to treat genetic information as a proprietary trade secret, the consortium is making its rice genome data freely available to all researchers.

The completed rice genome will be "indispensable" in the effort to boost harvests to meet a global appetite expected to grow 30 percent over the next 20 years, said Takuji Sasaki, vice president of the National Institute of Agrobiological Sciences in Tsukuba, Japan. He is the senior scientist in charge of the International Rice Genome Sequencing Project.

Because rice is the first cereal crop to be fully analyzed, researchers expect that such intimate knowledge of the genetics of rice will unlock the heredity of other more complex grains, including corn, wheat and barley.

"Rice is the Rosetta Stone for crop genomes," said Robin Buell, who led the rice sequencing effort at the Institute for Genomic Research in Rockville. "We can start to ask what makes a cereal a cereal."

The Los Angeles Times is a Tribune Publishing newspaper.

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