Rice Genome Sequence Means More Food for the Future

TSUKUBA, Japan, August 15, 2005 (ENS) - Scientists with the International Rice Genome Sequencing Project have published the DNA pattern for rice - the first crop plant to be completely decoded. Scientists around the world will use the new information to improve yields of rice and also other related grass crops such as barley, corn, rye, sugarcane and wheat.

More than half the world's growing population relies upon rice as a staple food, but worldwide environmental degradation has decreased rice production for the past four years. The newly published sequence offers the hope that rice yields can be increased to keep pace with demand.

Child in Ghana enjoys his bowl of rice. Ghanians consume around metric 110,000 tons of rice per year. (Photo by P. Cenini courtesy FAO)

Analysis of the rice genome, reported in Thursday's issue of the journal "Nature," made public the location and sequence of over 37,500 protein-encoding genes in 389 million bases of DNA. By comparison, the human genome has 25,000 genes, so this important food crop has more genes than humans.

"Knowing the sequence of one of the world's most important crops, will be invaluable to plant genomics researchers. This project will potentially help millions of people around the globe," said Arden L. Bement, Jr., director of the U.S. National Science Foundation, which funded part of the research.

Agricultural experts estimate that world rice production must increase by 30 percent in the next 20 years to keep pace with the growing world population.

Originally planned as a 10 year project, the rice genome sequence was completed in six years due to sharing of materials, data, and technology among researchers from publicly funded laboratories in 10 countries who make up the International Rice Genome Sequencing Project.

Established in 1998, the Japanese led IRGSP consortium includes Brazil, China, France, India, Korea, Taiwan, Thailand, the United Kingdom, and the United States.

"This is one of the most accurate and complete sequences from a higher organism," the IRGSP said. "The sequence was obtained through the clone-by-clone sequencing strategy. The accuracy of the sequence data is maintained at 99.999% corresponding to less than one error per 10,000 bases so that the reliability of identified genes is also high."

Rice is the staple food for more than half the world's people. (Photo by Keith Weller courtesy USDA)

The newly complete sequence builds upon earlier draft sequences published by private companies Monsanto and Syngenta, which donated their genome sequences to the IRGSP, saving the public consortium time and money.

"This is a monumental achievement. Enough credit cannot be given to the IRGSP members for working together to advance the research of such an important world crop," said Mary Clutter, assistant director for NSF's biology directorate.

The japonica subspecies of rice, which is cultivated in Japan, Korea and the United States, was the type of rice analyzed.

The group made public a draft sequence of the japonica genome in late 2002. Since then, IRGSP scientists have increased the quality of the sequence to 95 percent complete at greater than 99 percent accuracy.

The accurate, map based sequence of the rice genome has already led to the identification of genes that affect the plant's growth habit to promote yield and photoperiod genes to extend the range of elite cultivars. Scientists have used the finished sequence to identify genes that control fundamental processes, such as flowering.

The drought that is parching much of Asia this year will cost the region hundreds of millions of dollars in lost agricultural production and drive millions of people into poverty. A better scientific understanding of how a rice plant tolerates drought could help rice breeders to develop varieties that can withstand the dry years.

Man transplants rice seedlings, Nueva Vizcaya, Philippines. (Photo by J. Villamora courtesy FAO)

Rice has a smaller genome than maize and wheat, making it a better candidate for sequencing yet the rice genome is largely co-linear with other cereal genomes. Similar genes in the other plant species should appear in roughly the same spots as their rice counterparts.

"Rice is the Rosetta Stone for crop genomes," Buell says. "We can use the rice genome as a base for genomic studies of cereals."

Rice's similarity to barley has helped researchers identify genes responsible for resistance to barley powdery mildew and stem rust, two major crop diseases.

Every year, the world consumes over 880 billion pounds of rice, but rice plants provide more than food. The grain is fermented into wine. Rice straw makes cattle feed, paper, rope and bricks. Rice oil goes into soap and cosmetics, and seed hulls provide fuel for simple stoves and packing material for fragile cargo.

Technical details and access to the sequence are online at: http://rgp.dna.affrc.go.jp/