Research Accomplishment Reports 2010

The Regulation of Innate Immune Responses to Endoparasites in Lepidopteran and Dipteran Larvae

B.A. Webb, S. Govind
Department of Entomology

 

Non-Technical Summary

Immune responses of insects to parasitic wasps are poorly understood but criticial to the efficacy of biological control in natural and agroecosystems. This project will describe the basic immune responses to allow better prediction of the results of biocontrol and possibly identify important genes from insects that could be useful for insect control.

2010 Project Description

This project compared two parasitoid-host systems one with and one without a polydnavirus. The virulence factors of one system were produced in a supracellular system of actin-lined canals that controlled the biogenesis and release of those virulence factors from the parasitoid venom glands. These factors markedly affected the transcription of immune genes. Similarly, in the polydnavirus-containing system insect immune responses against against microbial challenge, polydanviruses and parasitoids were described.

We hypothesized that the regulation of host immune responses determines the success of parasitization for the endoparasitoid Campoletis sonorensis in its lepidopteran host. A EST chip was designed and analyzed to test this hypothesis. From 44,844 Heliothis virescens ESTs, 15,305 putatively different transcripts were used to construct a custom microarray.

Combining the microarray results with qPCR, we found parasitization inhibited cecropin, gloverin, lebocin and attacin expression in host hemocytes. Attacin expression was inhibited in host hemocytes and fat body tissues following parasitization and LPS injection. The findings provide novel information about the regulation of lepidopteran immune system after C. sonorensis parasitization and that CsIV is an immunosuppressive factor of the host immune responsive genes regulated via NF- κB signaling.

2010 Impact

The immunological responses of hosts to parasitoids and the ability of parasitoids to overcome those responses determines the host range and biological success of these important biocontrol agents. By taking a genomic approach that is also comparative in nature we begin to define the common host systems that are suppressed by polydnaviruses or venom in the two respective systems. The conserved elements in the two systems are likely to be the most important and potentially targets for newly developed insect control strategies.