The key to the improvement in the genome sequence analysis is that the researchers have used the combined DNA sequence data from the two subspecies to facilitate the sequence assembly. The result is a nearly 1,000-fold increase in contiguity for the two genome sequences relative to the existing sequence data.
The researchers have used their improved genome sequence to investigate the evolutionary history of rice. Central to evolution is the development of new functions through mutation of existing genes. But when mutations occur in functional genes, the result is rarely beneficial, so it is thought that evolution is more likely to proceed first by duplicating existing genes and then experimenting on the "backup" copy of the gene.
Wong and colleagues report that there is evidence in the rice DNA sequences for a whole-genome duplication event just before the grasses diverged from other flowering plants, about 5570 million years ago. This genome duplication may have played a role in the origin of the grasses, which then spread rapidly across the world to provide important sources of food that, among other things, possibly influenced human evolution.
Analysis of the rice genomes also indicates that there is massive ongoing duplication of individual genes. These individual gene duplications provide a continuous source of raw material for gene genesis and very likely contribute to the differences between members of the grass family. Now the challenge is to use the rice sequences as a basis for detailed genetic analyse
Contact: Paul Ocampo
Public Library of Science