Virus with a Multipartite Superhelical DNA Genome from the Ichneumonid Parasitoid Campoletis sonorensis

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Abstract
Virus was isolated from the lumen of the calyx region of ovaries in the parasitoid wasp C. sonorensis (Hymenoptera: Ichneumonidae), and the nature of the viral DNA was analyzed. DNA purified from a homogeneous band of virus contained double-stranded superhelical molecules which were polydisperse in MW. At least 25 different covalently closed circles were present, ranging in MW from 4.0-13.6 .times. 106. The virus DNA was analyzed with restriction enzymes, and the nature of the genetic complexity was evaluated by Southern blot hybridization of native superhelical and relaxed circular virus DNA and SalI- and HindIII-digested DNA. Evidently, most of the variously sized covalently closed DNA were composed primarily of nonhomologous sequences. The different size classes of covalently closed viral DNA did not appear to exist in equimolar concentrations. There was no evidence for observation of virus particles by EM or from virus fractionation experiments that a mixture of viruses was present in the calyx fluid. Thus, the virus isolated from C. sonorensis, like those isolated from other endoplasmic hymenoptera, may belong to a new class of DNA viruses in which the genome is multipartite, with each DNA existing as a superhelical molecule.