by Piyaporn Hawiset
6 April 2002
Scientists in April 2002 laid bare the "life code" of rice. Two groups of researchers reported a draft DNA sequence of the plant - a staple for more than half the world's population - in the journal Science. The genetic information should speed up the breeding of tougher and higher-yielding varieties that could help feed the world's burgeoning population. The genomic data would also prove invaluable in boosting the productivity of the other grasses on which humans depend, such as maize (corn) and wheat. The research shows that a rice plant probably has more genes than a human - perhaps as many as 50-60,000 genes, compared with our 30-40,000.
But the rice genome, like the gene sets of all plants, contains tremendous duplication. Something like three-quarters of all rice genes are repeated in the code.
Much duplication
Scientists think plants copy their genes and then modify them as a strategy for coping with the selective pressures associated with evolution.
The Beijing Genomics Institute and the University of Washington Genome Center, with colleagues at 11 Chinese institutions, read the code of the rice strain known as indica, the predominant subspecies in China and other Asian-Pacific countries. The second team, fronted by the Swiss-based Syngenta company, decoded the japonica, or Nipponbare, subspecies, which is popular in more arid regions and, in particular, Japan. The genetic difference between the two is small but significant - about a half to one percent variation in the code. This is about 10 times the variation you would find in the genetic codes of two humans.
Rice, known scientifically by the Linnean name Oryza sativa, was the second plant to be decoded. The first was the tiny mustard plant, Arabidopsis thaliana, used as a laboratory model to investigate plant biology. Rice, however, was the first food crop to be sequenced.
Another method
Both teams used the Whole-Genome Shotgun technique, the same method employed by the private company Celera to read the human "code of life". And just like Celera, Syngenta struck a deal with the Science journal editors that would ensure it would keep proprietorial control over the japonica sequence. The code was not deposited in a public database, GenBank, as is customary, but in an escrow account held by Science and a separate system run by Syngenta.
Researchers wanting to work on the sequence would have to sign usage agreements with the Swiss company. Critics claimed the access restrictions go against the spirit of open research and would slow the advance of new knowledge. A consortium of public laboratories, known as the International Rice Genome Sequencing Project (IRGSP), financed by Japan, has also sequencing the Nipponbare subspecies.
The consortium opted to use a more systematic, traditional route to decryption which, though more precise, can take longer. The IRGSP was expected to publish its results later in 2002.