Related Wasp and Polydnavirus Genes: Role in Parasitism

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Some insect parasites inject secretions into the host along with their egg which results in avoiding immune defenses and causes host developmental arrest. For Campoletis sonorensis, both phenomena may be induced by a polydnavirus (PDV). PDV is the only animal DNA virus with a heterogeneous, segmented genome. Several viral gene families have been identified that are expressed during parasitism, and viral gene expression is tissue and/or host specific. Through evolution the parasite has acquired to assemble, amplify and transfer this genetic information in a viral form to another eucaryotic host which is essential for parasite survival. We have shown one family of the venom related (VR) wasp and PDV genes encode structural motifs that belong to "DEAD" protein family. This suggests that these unique genes may encode products involved in regulating, splicing or translation. Our recent studies show also that CsPDV genes contain sequences that encode a cysteine motif characteristic of peptide toxins. The presence of this motif is unlikely to be fortuitous, rather it may reflect a function as a ligand of cell surface receptors which may also be correlated with functions related to parasite survival. The significance of this study emphasizes the molecular basis of parasite induced avoidance of insect defense systems and the research conducted with NSF support will be directed to identifying these expression products and determining their functional significance.