Rice Genome Mapped

In late January of this year [2001], two private companies announced that they have mapped the entire genome (i.e. all of the genes) of the rice variety ‘NIPPON barre.’ Rice is only the second plant (and the first agronomically important plant species) to have its genome decoded. Only recently was the genome of the first plant, a small weed (Arabidopsis thaliana) often used in research, decoded.

Genetic material is stored in genes, and many genes together make up a chromosome. Rice has 12 chromosomes containing a total of approximately 50, 000 genes. The 50,000 genes are made up of 430 million chemical subunits called bases of DNA. There are only four different subunits, and they are repeated. The sequence of these subunits makes up an individual gene and determines its properties. To decode the genome means to determine the entire sequence of the subunits in all 50,000 genes. Although the functions of many of the 50,000 genes are known, the function of about 20% of them has not yet been determined. The similarity between the various cereal crops means that the genome of rice will serve as a blueprint for similar crops such as wheat and corn.

The completed DNA sequence will not be published. However, the two companies, Syngenta and Myriad, will make it available to researchers worldwide through research contracts. Syngenta has a policy of working with local research institutes in the developing world to explore how information can be used to develop products for subsistence farmers, without charging royalties or technology fees. Syngenta was recently formed as a result of a merger between Novartis and AstraZeneca, and is the world’s largest agribusiness with about $7 billion in sales in 1999.

The knowledge of rice’s genome will be used by plant breeders to develop new varieties of rice. Knowledge of the precise locations of specific genes will also allow biotechnologists to identify and transfer individual genes between cultivars. It is expected that the information will have an impact on new rice varieties within the next five years.