Research Accomplishment Reports 2010

Genomic Approaches to Analyses of Immune-suppressive Genes of the Campoletis sonorensis Polydnavirus

B.A. Webb
Department of Entomology

 

Non-Technical Summary

Control of insect pests requires novel approaches on an ongoing basis because insects have demonstrated the ability to evolve resistance to many insect control practices. This project seeks to develop novel approaches to insect control that take advantage of new means to suppress the insect immune system.

2010 Project Description

In 2010, this project has discovered a novel virus that plays an integral part in the biology of the Campoletis sonorensis wasp, lepidopteran host and polydnavirus system. This novel virus is a cypovirus that is closely related to other lepidopteran cypoviruses, but has some unusual properties. Notably, the newly discovered cypovirus appears to be able to replicate in both the lepdidopteran host and the parasitic wasp.

Furthermore, replication in the parasitic wasp has a deleterious effect on the wasp while the cypovirus had no measurable effect on development and weight gain in the lepidopteran larvae.

Further, investigation of this phenomenon has shown that the cypovirus exists in two variants. Variant1 is preferentially associated with the parasitic wasp while variant 2 is preferentially found in the lepidopteran host.

We have developed a working hypothesis that the novel cypovirus may enhance survival of lepidopteran larvae directly by activating immune responses that enable survival of parasitized larvae and have a negative effect on wasp survival. We have initiated efforts to define the molecular differences between the two variants and detail how the two viral genomes are interacting relative to the lepidopteran immune system.

2010 Impact

Our discovery of the apparent negative effect of lepidopteran cypoviruses on parasitic wasps suggest that cypovirus infections, which are common but little studied in lepidopteran larvae, may directly reduce the efficacy of parasitic wasps and potentially of other biocontrol agents. Biocontrol agents are of increasing importance in agroecosystems so understanding the factors that limit the efficacy of biocontral agents is of considerable importance.

On a more speculative note, it appears that lepidopteran larvae may, in effect, have a viral defense against parasitization. If this turns out to be the case it would be a novel finding of fundamental importance to our understanding of the interactions between pathogenic and commensal viruses in wasp-parasitoid systems.