Polydnaviruses (PDVs) are a group of viruses that exist in obligate mutualism with certain members of ichneumonid and braconid wasps. These viruses have a segmented, double-stranded DNA genome which makes them unique among virus families. PDVs are divided into two genera, ichnoviruses (IVs) and bracoviruses (BVs) based on their wasp assoication. Although phylogentic studies indicate that the association between these viral groups and parasitoids arose independently, IVs and BVs share similar life cycles and produce similar pathologies in infected lepidopteran hosts. Microplitis demolitor bracovirus (MdBV) is the best characterized bracovirus, and is the focus of our current sequencing project. MdBV consists of 15 segments ranging in size from 4 to 26 kb, yielding an aggregate genome size of ~210 kb. The MdBV genome is largely non-coding, ~86% to this point, despite the presence of four multi-gene families. Segments O and K occur in hypermolar ratios compared to less abundant segments such as A. Interestingly, the only two gene families confirmed for MdBV, the EGF-like genes and Glc genes, reside on segment O. More recently, we have identified two additional putative gene families by BLASTX similarity to protein-tyrosine phosphatases and Nf-KB inhibitory proteins (also present in CsIV). If the Nf-KB genes are indeed expressed, this will be first instance of a shared gene family between BVs and IVs. With the complete sequence of the MdBV genome we can examine questions regarding the origin, evolution, and relationships between PDVs through comparative genomics.
Species 1: Hymenoptera Braconidae Microplitis demolitor
Species 2: Lepidoptera Noctuidae Heliothis virescens (Tobacco budworm)
Keywords: polydnavirus
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