The genes of some plants consist of more than 90 percent transposable elements, while in others the percentage may be less than 20 percent. Overall, however, transposable elements are a huge part of most genomes. The answer is that we do believe they play a significant role in genetic function and diversity. The team's first step will be to identify by computer methods all the transposable elements in the rice genome. They will then study the elements in Wessler's lab, developing them as molecular markers to see if any of them are biologically active and contribute to genome diversity.
Researchers believe some are activated in response to environmental stress.
Transposable elements may provide a way to diversify the genome in response to environmental changes. Rice, corn, barley, wheat and sorghum are all grasses, and each species has numerous varieties bred over the centuries by farmers and scientists. The mechanisms behind all this genetic diversity is poorly understood, however, and transposable elements may play a major role in many of the plants' differences, such as size. What we need to know is whether this diversity has functional consequences. If successful, this project will go al long way toward answering that question.