[Polydnaviruses, a unique example of viral machinery domesticated by parasitoid wasps]

Polydnaviruses are unique mutualistic viruses associated with thousands of parasitoid wasps. They are characterized by a segmented packaged DNA genome and are necessary for parasitic success. Virus particles are produced in the wasp ovaries from a set of "viral" sequences integrated into the wasp genome. The polydnavirus/wasp associations as observed today result from the integration of a viral genomes into the wasp genome during evolution. Recent years have been marked by the discovery of the viral ancestors of the two known types of polydnavirus, bracovirus and ichnovirus, which has helped to shed some light on the evolution of the symbiosis. Some of the viral genes have been conserved in the genome of the parasitoid, allowing the latter to produce non-replicative viral particles, that contain DNA molecules encoding essentially "virulence" genes, probably of insect origin. Thus polydnaviruses can be considered as endogenous viral elements (EVE) that have been domesticated by the wasp to become a "weapon" allowing its survival.