Why is the rice genome important to non-rice growers?

1. Rice is a model cereal plant.

Rice, apart from being a staple food for several billion people, is also a model system for cereals. For the rest of the world, other cereal crops, such as wheat, corn, sorghum and barely (among others) form the basis of most people’s “daily bread”. Rice is of particular use as a model for these other cereals because of the small size of its genome (430 Mb), its relatively short generation time and its relative genetic simplicity (it is diploid, or has two copies of each chromosome). Moreover, rice is quite easy to transform genetically. Wheat, in contrast, has a genome 40 times as large as rice, and can be diploid, but is more commonly tetraploid (4x), such as in durum wheat, or hexaploid (6x), such as in bread wheat. Each additional set of chromosomes adds complexity to genetic studies. But how can rice act as a model for other cereals? The most striking feature of the cereals is that, despite huge differences in genome size and ploidy, the genomes of rice and the other cereals are highly conserved. This conservation occurs not only in the sequences of the genes present, but in the order of the genes, or “synteny”.

2. Similarity between rice and other plants.

Rice and other plants, especially other cereals, are amazingly similar on a genetic level. For example, the genes are often present on the chromosomes in the same order (synteny), and moreover, the genes themselves are very similar at a sequences level (homology). This is important if the granted rice patent covers, through “homology” or “percent identity” language, a gene in other another cereal, such as maize or wheat. This means that when when patents contain broadening language, including percent identity language, they may literally cross-cover other species. That is, a patent on a rice gene with, for example, percent identity language, may actually cover genes in wheat, or barley, or even bamboo! This means that researchers in another field may be unwittingly infringing patents on rice.  (Note however, that because of recent changes in U.S. patent law, a court is likely to interpret the claim to cover only rice.)

3. Rice is the first major crop genome to be sequenced.

Patenting and research behavior resulting from rice genome data may have an impact on how other crops are handled in the future. In the years since the rice genome was sequenced, there have been tremendous improvements in high-throughput DNA sequencing. As a result, there has been an explosion in the number and variety of genomes that have been sequenced. It is likely that the disclosures and claims of some of the more recently-sequenced plant genomes will be modeled on the patenting behaviour of the rice genome.

Because many rice genome patents were filed before the related crop species were sequenced, there was relatively little sequence-based prior art to be found by patent examiners. As a result, earlier plant genome patents are likely to be broader in scope than later applications.