Submitted to: Journal of General Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/30/2003
Publication Date: 8/1/2003
Citation: Chen, Y., Gundersen, D.E. 2003. Morphological and genomic characterization of the polydnavirus associated with the parasitoid wasp, glyptapanteles indiensis (hymenoptera: braconidae). Journal of General Virology. Interpretive Summary: Lepidopteran caterpillars are successfully parasitized by a variety of wasps in the ecosystem. Polydnaviruses are unique viruses carried by a large number of economically important parasitoid wasps. During oviposition, polydnaviruses are injected into the caterpillar along with wasp's eggs. Within the caterpillar host, polydnaviruses play an essential role in the survival of the parasitoid wasp, by disrupting the host's cell immune response. Yet this virus has not been characterized. In the present study, the structural features and genomic organization of one polydnavirus were characterized. This is the first detailed characterization of a Braconid polydnavirus. The virus was found to be oval-shaped and to have multiple genomic DNA segments. Two new viral genes were isolated from the host and found to be present on more than one of the DNA segments. This study provides a fundamental basis for explaining how polydnavirus assists in the wasp's survival. This information will be of interest to the scientific community and to biological companies because the gene encoded proteins may have great potential in future biopesticide development.
Technical Abstract: Glyptapanteles indiensis polydnavirus (GiPDV) is essential for successful parasitization of the larval stage of the lepidopteran Lymantria dispar (gypsy moth) by the endoparasitic wasp, Glyptapanteles indiensis. This virus has not been characterized. Ultrastructural studies of GiPDV showed that the virions had an oval-shaped form and each virion contained as many as ten nucleocapsids enclosed by a single unit membrane envelope. Field Inversion Gel Electrophoresis (FIGE) analysis revealed that GiPDV had a segmented genome composed of 13 ds DNA segments, ranging in size from approximately 11 kb to more than 30 kb. Four genomic segments were presented in higher molar concentration than the others. Further characterization of the GiPDV genome yielded several cDNA clones which encoded GiPDV-specific mRNAs and were expressed in the parasitized host. Each was present on more than one GiPDV genomic DNA segment, suggesting the existence of homologous sequences among DNA segments or nested genomic segments. It has been proposed that in polydnavirus systems, genome segmentation, hypermolar ratio segments and segment nesting may function to increase the copy number of essential genes and to increase the levels of gene expression in the absence of virus replication. The present data support this notion and suggest that GiPDV morphology and genomic organization may be intrinsically linked to the function and evolutionary strategies of the virus.