Abstract
Campoletis sonorensis polydnavirus (CSPDV) gene products induce alterations in the normal development and cellular immune responses of its lepidopteran host Heliothis virescens, required for survival of its associated endoparasitic hymenopteran host. One of the central goals in the study of this and other parasitoid systems is the identification of polydnavirus gene products which mediate these effects. This is complicated by the size and complexity of polydnavirus genomes. These effects may also be mediated by multiple factors. At least two CSPDV gene families are expressed in the parasitized H. virescens host. The patterns of expression and localization of gene products encoded by two CSPDV gene families were analyzed to develop a better understanding of CSPDV gene family functional significance in the parasitized H. virescens host. An imperfectly conserved polypeptide domain averaging 180 amino acids in length was found singly or tandemly repeated in 3 different rep gene family encoded proteins. These 3 rep proteins were detected in the hemocytes of parasitized H. virescens larvae by immunoblot analysis, but no alterations in granulocyte morphology or adhesiveness was observed following recombinant baculovirus expression of the BHvO.9 rep gene in H. virescens hemocytes. Two members of the CSPDV cys-rich gene family, WHvl.O and WHvl.6, were also shown to be expressed in hemocytes. These proteins were however secreted and found-in the hemolymph of the parasitized H. virescens host as early as 4 hours post-parasitization. Both of these proteins specifically bound and were internalized by unparasitized H. virescens granulocytes in vitro. Mutants containing deletions of the WHvl.6 pre-cys, cysrich, and carboxy-terminal domains were still capable of binding H. virescens granulocytes. The specific association of these two cys-rich proteins with granulocytes implicates them in the abrogation of the host cellular encapsulation response and suggests that members of this protein family may act cooperatively.
Graham, Brent Lee (1996). Analysis of the expression and localization of gene products from two Campoletis sonorensis polydnavirus multigene families. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1996 -THESIS -G734.