Polydnavirus Genome Organization

Polydnavirus DNA of the braconid wasp Chelonus inanitus is integrated in the wasp's genome and excised only in later pupal and adult stages of the female

“…In the only other polydnavirus-wasp system where integration/ excision regions have been sequenced, the ichnovirus of C. sonorensis, some similar observations were made. Short imperfect direct repeats of 59 nucleotides were found at both termini of integrated virus DNA and a single copy was found in the virus DNA (Fleming & Summers, 1990Fleming & Krell, 1993). Rejoining of genomic DNA was not investigated in this system but the presented sequence data are compatible with the model of excision that we propose for the bracovirus of C. inanitus in Fig.…”

“…The mechanism utilized for ichnoviruses appears to be integration of virus DNA into the wasp's genome. Several segments of the ichnovirus of Campoletis sonorensis were detectable as off-size restriction fragments in male and female somatic tissue (Fleming & Summers, I986;Fleming & Krell, 1993) and for one virus segment integration into the wasp genome has been unequivocally demonstrated (Fleming & Summers,199I (Xu & Stoltz, 1991). For bracoviruses the mechanism of transmission of virus DNA (integrated into wasp genomic DNA or episomal) is still unclear.…”

“…Polydnaviruses are characterized by having polydisperse dsDNA genomes and occur in parasitic wasps of the families Ichneumonidae and Braconidae (reviewed in Fleming, I992;Fleming & Krell, 1993;Stoltz, 1993). Accordingly, they are classified as the genera Ichnovirus and Bracovirus (Francki et aI., 1991).…”

“…Ichnovirus particles consist of lenticular nucleocapsids of usually uniform size and are surrounded by two unit membrane envelopes. Bracovirus particles, on the other hand, consist of nucleocapsids of uniform diameter but of variable length and may contain one or more nucleocapsid within a single unit membrane envelope (reviewed in Stoltz & Vinson, 1979;Fleming & Krell, 1993 The sequence data reported in this paper have been deposited in the EIBL database and assigned the accession numbers Z58828 and Z58830-Z58832, replicate only in the nuclei of calyx ceils of wasp ovaries from where they are secreted into the oviduct and injected into the host egg or larva (reviewed in Stoltz, 1993). Polydnaviruses are of crucial importance for survival of the parasitoid larva as they play a role in abrogation of the immune response against the parasitoid (reviewed in Lavine & Beckage,I995) and in host regulation (reviewed in Lawrence & Lanzrein, 1993;Stoltz, 1993).…”

Polydnavirus infection inhibits synthesis of an insect plasma protein, arylphorin

“…Polydnaviruses replicate only in the calyx cells of the female reproductive tract, bud into the oviduct lumen and are injected, along with the wasp egg, venom and ovarian proteins, into host insects during parasitization (for reviews see Fleming, 1992;Fleming & Krell, 1993;Stoltz & Whitfield, 1992;Beckage, 1993). The Campoletis sonorensis polydnavirus (CsPDV) has been characterized to the greatest extent at the molecular level.…”