Virus World

Researchers shed light on the important role that microbial genes, like those from viruses, can play in insect and animal evolution. Jennifer Brisson, an associate professor of biology at the University of Rochester, and her former postdoctoral student Benjamin Parker, now an assistant professor of microbiology at the University of Tennessee, studied phenotypically plastic traits in pea aphids and uncovered, for the first time, genes that influence whether aphids produce wingless or winged offspring in response to their environment. Pea aphids are insects that reproduce rapidly and typically give birth to offspring that do not have wings. When an environment becomes too crowded with other aphids, the females begin producing offspring that have wings, rather than the typical wingless offspring. The winged offspring can then fly to and colonize new, less crowded plants. The researchers used techniques from evolutionary genetics and molecular biology to identify genes that determine the degree to which aphids respond to crowding. Surprisingly, the genes they uncovered are from a virus that then became incorporated into the aphid genome. The virus, which is from a group of insect viruses called densoviruses, causes its host to produce offspring with wings. Most laterally transferred DNA -- DNA that is inherited from other organisms, like viruses -- is not expressed by its hosts because it is quickly inactivated or eliminated. However, there are examples in most organisms -- even humans -- where genomes co-opt genes laterally; in humans, for instance, the gene that creates a membrane between the placenta and the fetus was co-opted from a retrovirus.