Genomes are thought of blueprints-- collections of the genetic instructions for development and function and organisms. But genomes also contain other material, often including substantial amounts of parasitic DNA, in the form of transposable elements (TEs). TEs act as parasites by using their host genomes replication and metabolic machinery to reproduce themselves. They are successful parasites when they replicate within genomes faster than their hosts' own genes; in fact, they can be so successful that they make up major fractions of the genomes of a wide variety of organisms.
Like many parasites, TEs can also be harmful: as they replicate within genomes, they necessarily break the backbone of the DNA molecule, which can disrupt host genes and threaten the integrity of the genome. Hence, organisms have evolved to repress TE replication, especially in reproductive cells (e.g. eggs and sperm), where new mutations can be transmitted to offspring. As a result, active TEs tend to be those that have only recently invaded host genomes from another species.
In this project, we are investigating the evolution of host repression of TEs, taking advantage of an active TE that has recently invaded a fruit fly (Drosophila) species. Most similar work focuses on females, where transposable elements can have a major effect on fertility. Here, we focused on males. First, we asked if the TE also has a negative effect on male fertility, showing that it does. Second, we asked if the flies have evolved suppression of the TE in the testes as a result; results from this part of the project are forthcoming.
As a result of their important impact on the genomes of so many organisms, understanding the basic biology of TEs is a societal good, which may have long-term benefits in understanding the biology of genetic disease.
