Pattern of gene duplication in the Cotesia congregata Bracovirus

Polydnaviruses (PDVs) are a family of double-stranded DNA viruses genetically linked to their wasp hosts. These viruses utilize the transcriptional machinery of the wasp cells to manufacture viral particles which contain circular segments of DNA. The female wasp, hosting the polydnavirus, lays its eggs along with the viral particles inside a caterpillar. Because no replication of the virus occurs while inside the caterpillar, fixed genetic changes occur solely inside the female wasp, as an integrated portion of its genome. Therefore, evolution of the polydnavirus is expected to parallel that of the wasp. Phylogenetic analysis of the polydnavirus genome showed a pattern of gene duplication consistent with the “birth-and-death” process frequently observed in eukaryotic genomes. Phylogenies provided no unequivocal evidence of horizontal gene transfer between the wasp host and the polydnavirus, but in some cases there were suggestions of such gene transfer.