Rockville, MD -- Every year, the world consumes over 880 billion poundsof rice, which feeds half the population. Those tiny grains add up. Somaybe it's no surprise that this important food crop turns out to havemore genes than humans.
It's certainly not to researchers at The Institute for GenomicResearch (TIGR), who have been sequencing the first food crop genome aspart of an international consortium for the last six years. Thecompleted sequence, published in the August 11 issue of Nature, unveils a genome consisting of roughly 400 million DNA bases holding 37,544 genes on rice's 12 chromosomes.
"Rice is a critically important crop, and this finished sequencerepresents a major milestone," said Robin Buell, lead investigator forTIGR's portion of the project. "We know the scientific community canuse these data to develop new varieties of rice that deliver increasedyields and grow in harsher conditions."
Over the next 20 years, world rice production must increase bya projected 30% to feed the earth's growing population. This finishedsequence will provide an indispensable roadmap to agriculturalresearchers using both biotechnology and conventional breeding todevelop hardier rice varieties. The genetic map will greatly speedtheir hunt for genes that increase yield, protect against disease andpests, or provide drought-resistance in rice and other cereal crops.Rice is genetically similar to maize, wheat, barley, rye, sorghum, andsugarcane.
"Rice is the Rosetta Stone for crop genomes," Buell says. "Wecan use the rice genome as a base for genomic studies of cereals." Sheadds that rice has a considerably smaller genome than maize and wheat,making it a better candidate for sequencing. Luckily, though, the ricegenome is largely co-linear with other cereal genomes. In other words,similar genes in the other plant species should pop up in roughly thesame spots as their rice counterparts. With the finished sequence, riceresearchers gain a kind of genetic GPS, while other cereal researchersinherit a hand-drawn map with some important landmarks.
TIGR researchers sequenced more than 10% of the genome of the temperate subspecies of rice, Oryza sativa subspecies japonica,which is cultivated mainly in Japan, Korea, and the U.S. Their effortwas part of the International Rice Genome Sequencing Project (IRGSP),which began in 1998 and pooled the resources of groups from tennations, including Japan, China, India, Thailand, Taiwan, Brazil,France, Canada, the United Kingdom, and the United States. Japan leadsthe IRGSP.
The newly complete rice genome builds upon earlier draftsequences published by private companies Monsanto and Syngenta. In whatBuell calls a "nice model of a public-private partnership," thesecompanies donated their genome sequences to the IRGSP, saving thepublic consortium both time and money.
"Much as the Human Genome Project has revolutionized biology,the rice genome promises to inspire new cereal crop research," remarksTIGR President Claire Fraser. "This is a major step forward foragriculture."
Already, in fact, the finished rice genome is acceleratingdiscovery. Scientists have used the finished sequence to identify genesthat control fundamental processes, such as flowering. Rice'ssimilarity to barley also has helped researchers identify genesresponsible for resistance to barley powdery mildew and stem rust, twomajor crop diseases.
In the current study, researchers compared rice to the only other fully sequenced plant genome: Arabidopsis thaliana, a leafy plant that is a popular laboratory model. While 90% of Arabidopsis proteinsalso occur in rice, only 71% of rice's proteins also occur inArabidopsis. That, says Buell, suggests that rice may hold manyrice-specific or cereal-specific genes.
Along with TIGR, other U.S. groups involved in sequencing thegenome included Cold Spring Harbor Laboratory, the University ofArizona, Rutgers University, Washington University in St. Louis, andthe University of Wisconsin-Madison. Major funding for TIGR's portionof the project came from the U.S. Department of Energy, the NationalScience Foundation, and the U.S. Department of Agriculture'sCooperative State Research, Education, and Extension Service.
The rice project is an important part of TIGR's plant genomicsprogram, which includes other major research projects involving maize,potato, and Arabidopsis. TIGR is also conducting research involvingpine, barley, banana, and plant pathogens. Work on rice at TIGRcontinues with a four-year project to annotate the genome--identifyingits features, assigning known information to each gene, and creatingcomparative line-ups with other plant species. The finished rice genomeis available at www.tigr.org/tdb/e2k1/osa1/.
The Institute for Genomic Research (TIGR) is a not-for-profit researchinstitute based in Rockville, Maryland. TIGR, which sequenced the firstcomplete genome of a free-living organism in 1995, has been at theforefront of the genomic revolution since the institute was founded in1992. TIGR conducts research involving the structural, functional, andcomparative analysis of genomes and gene products in viruses, bacteria,archaea, and eukaryotes.
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