Science |Wasps have injected new genes into butterflies
If you’re a caterpillar, you do not want to meet a parasitic wasp. The winged insect will inject you full of eggs, which will grow inside your body, develop into larvae, and hatch from your corpse. But a new study reveals that wasps have given caterpillars something beneficial during these attacks as well: pieces of viral DNA that become part of the caterpillar genome, protecting them against an entirely different lethal virus. In essence, the wasps have turned caterpillars into genetically modified organisms.
“The key strength of the study is it clearly demonstrates that [viruses] have been a source of horizontal gene transfer for some insects,” says parasitic wasp expert Michael Strand of the University of Georgia, Athens, who was not involved in the study.
Study author and biologist Jean-Michel Drezen of François Rabelais University in Tours, France, has been studying the parasitic relationship between the wasps and their lepidopteran (butterflies and moths) victims for decades. He specializes in bracoviruses, which are injected by the wasps along with their eggs. Once inside the caterpillar, the bracovirus prevents a normal immune response by disrupting the cell’s cytoskeleton—a network of filamentlike proteins responsible for moving components and machinery around the cell. Without an immune response, the wasp eggs are free to grow unchecked.
But the discovery that the caterpillars have taken up and repurposed bits of the wasp virus for their own means came as a surprise. "I couldn’t believe it,” Drezen says. “We did not expect this at all.”