The excision of polydnavirus sequences from the genome of the wasp Cotesia congregata (Braconidae, Microgastrinae) is developmentally regulated but not strictly restricted to the ovaries in the adult

Authors


Dr J.-M.Drezen Institut de Recherche sur la Biologie de l'Insecte–UPRESA CNRS 6035, Faculté des Sciences, Parc de Grandmont, 37200 Tours, France. e-mail: drezen@univ-tours.fr

Abstract

Cotesia congregata polydnavirus (CcPDV) is essential for the successful parasitism of Manduca sexta larvae by the braconid wasp Cotesia congregata. In the absence of PDV, parasitoid eggs are encapsulated. Molecular analysis has demonstrated that polydnavirus sequences are integrated in the wasp chromosomes, and an ultrastructural analysis has shown that PDV replication occurs in the calyx region in the ovaries of the wasp. The bracovirus sequences appear to be excised from the wasp genome in the calyx cells where the virus replicates. Following excision of the virus sequences, the flanking sequences are rejoined. We analysed the production of two polydnavirus circles during wasp development and in different body parts of the adults of both sexes. Our study indicates that the excision of viral sequences is developmentally regulated, beginning in the pupal stage. In the adult wasp, excision occurs ubiquitously. However, regulation in the adult seems to occur only in diploid individuals, as no excision is detected in haploid males produced from virgin females.

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