Research teams from the University of Valencia in Spain and the University of Tours in France have discovered that genes originating from parasitic wasps are present in the genomes of many butterflies. These genes were acquired through a wasp-associated virus that integrates into DNA. Wasp genes have now been domesticated and likely play a role in in protecting butterflies against other pathogenic viruses. These results, published online in the open-access journal PLOS Genetics on September 17, 2015, reveal that butterflies, including the Monarch, an iconic species for naturalists and well-known for its spectacular migrations, constitute naturally produced genetically modified organisms (GMOs) during the course of evolution. This finding “relativizes” the novelty of producing GM insects, because such insects already exist in nature, but also highlights that genes introduced in GM insects can be transferred between distant species. The PLOS Genetics article is titled “Recurrent Domestication by Lepidoptera of Genes from Their Parasites Mediated by Bracoviruses.” To reproduce, braconid wasps lay their eggs inside caterpillars and inject a “giant virus” named bracovirus to circumvent the caterpillars' immune response. Bracoviruses can integrate into the DNA of parasitized caterpillars and control caterpillar development, enabling wasp larvae to colonize their host. Bracovirus genes can be detected in the genomes of several species of butterfly and moth, including the famous Monarch (Danaus plexippus), the silkworm (Bombyx mori), and insect pests such as the Fall Armyworm (Spodoptera frugiperda) and the Beet Armyworm (Spodoptera exigua).
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