Scientists confirm rice-maize similarity

The smallest rice chromosome has nearly twice as many predicted genes as the draft DNA sequence had indicated, claims a rice genome sequencing team in the US.

The scientists report in the latest issue of Science​ that the new 'finished' sequence and analysis of rice Chromosome 10 confirms that the rice genome is closely similar to that of other grains, in particular sorghum and maize.

Robin Buell, who led the rice genome sequencing team at The Institute for Genomic Research (TIGR), said that the 'finished' sequence - which helped researchers identify about 1,700 additional rice genes -shows the importance of completing a draft DNA sequence. "The finished Chromosome 10 sequence of rice will be a major component for future comparative studies of other cereals, such as corn and wheat."​

Chromosome 10 was sequenced by a US group - led by Buell at TIGR and by Rod A. Wing at the university of Arizona - as part of the International Rice Genome Sequencing Project (IRGSP), a public effort to complete the sequences of all 12 rice chromosomes, which have a total of 430 million DNA base pairs.

The IRGSP has already sequenced the genome of the japonica subspecies of rice (Oryza sativa) that is cultivated in Japan, Korea and the United States. Another rice subspecies, indica, has been sequenced by a Chinese institute.

Buell said that the new study predicts a total of about 3,500 genes on Chromosome 10, which encompasses about 22 million DNA base pairs. The previous estimate, based on the draft genome blueprint, had predicted about half that number of genes.

Research into rice genomes - the data for which is freely available to all scientists worldwide - is expected to help plant scientists develop improved rice strains that are hardier and more productive. The draft sequence also provides an important tool for scientists who focus their research on other cereal crops (including maize, wheat and barley) with genomes that are colinear with rice.