[Understanding the evolution of polydnaviruses].

Described in thousands of parasitoid wasp species polydnaviruses (PDVs) are unique viruses having both a segmented DNA genome in viral particles and an integrated form that persists as a provirus in the wasp genome. Parasitoid wasps inject their eggs in another insect host and along with them, the virus particles that are essential to ensure parasitism success. Two phylogenetically unrelated genera of polydnaviruses exist, the bracoviruses (BVs) and the ichnoviruses (IVs) associated with braconid and ichneumonid wasps respectively. New data on the genomes of two bracoviruses (Microplitis demolitor BV and Cotesia congregata BV) and an ichnovirus associated with Campoletis sonorensis (CsIV) offers us new elements to discuss the central questions concerning the origin and the evolution of these viral entities. The results indicate that the tens of millions of years of mutualistic associations between PDVs and wasps has had a strong impact on PDV genomes that now ressemble an eukaryotic region.