The rice genome structure as a trail from the past to beyond.

Rice is the first cultivated plant species to be completely sequenced. Cultivation, in general, is a major factor that contributes to selection pressure of a target species resulting in accelerated changes in genome structure from an original wild species. The genome sequence of cultivated rice can now be used as a standard for comparison with many other cultivated rice species, its wild relatives and other grass species. Several indices define the dynamic nature of genome structure and function. Genome dynamics in rice is described here based on transposon, retrotransposon and polyploidy. Comparative studies with other related grass species based on the principle of synteny are expected to generate invaluable information that will clarify the trail that led to the present cultivated rice as well as the trail that will lead to its further improvement.