Submitted to: Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2013
Publication Date: 7/1/2013
Citation: Bezier, A., Louis, F., Jancek, S., Periquet, G., Theze, J., Gyapay, G., Musset, K., Lesobre, J., Lenoble, P., Dupuy, C., Gundersen, D.E., Herniou, E., Drezen, J. 2013. Functional endogenous viral elements (EVEs) in the genome of the parasitoid wasp cotesia congregata: insights into the evolutionary dynamics of bracoviruses. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences. 368:1-14. Interpretive Summary: Tiny wasps known as parasitoids have potential to control moth pests, such as caterpillars, of agricultural crops and forests. The survival of many of these wasps is enhanced by a virus, called a polydnavirus, that is injected along with the wasp egg into a host caterpillar pest. In this modern molecular techniques were used to sequence and characterize the provirus form of the virus that is a part of the Cotesia congregata wasp DNA before it is removed in certain ovarian cells to become free virus. This study represents the most comprehensive study of the provirus form, and new discoveries were made about the evolution of the virus. The information obtained will help explain how the polydnavirus may be formed in the wasp and replicate, how the virus may have been formed to help the wasp to survive, and may lead to new biocontrol strategies. This information will be of interest to university and industry scientists who are interested in virus evolution and/or in developing new virus-based strategies to control pests.
Technical Abstract: Bracoviruses represent the most complex Endogenous Viral Elements (EVEs) described to date. Nudiviral genes have been hosted within the genomes of parasitoid wasps since ~ 100 MYA (Million Years Ago) and are functionally integrated in the parasitoid wasp life cycle. They are involved in the production of bracovirus particles injected into parasitized lepidopteran hosts during wasp oviposition. These particles encapsidate multiple dsDNA circles encoding virulence genes expressed in the parasitized hosts and required for parasitism success. Here we report the analysis of proviral segments, i.e. master sequences producing the encapsidated dsDNA circles, present in the genome of Cotesia congregata. The genomic organisation consists of a macrolocus comprising 2/3 of the proviral segments and seven smaller dispersed loci each containing one to three segments. Comparisons of C. congregata bracovirus proviral loci with those of related species gave further insight into the evolutionary dynamics of bracoviruses. The nudiviral gene odv-e66-like1 is conserved in the macrolocus, suggesting an ancient co-localisation of the nudiviral genome and proviral segments. Moreover, synteny analysis showed most of the proviral genome is stably integrated at homologous loci in the genomes of different wasp species. In contrast, the evolution of proviral segments within the macrolocus has involved serial lineage-specific duplications.