VENOM OF THE ECTOPARASITOID, NASONIA VITRIPENNIS, INFLUENCES GENE EXPRESSION IN Musca domestica HEMOCYTES

Abstract

Insect hosts have evolved potent innate immunity against invasion by parasitoid wasps. Host/parasitoids live in co-evolutionary relationships. Nasonia vitripennis females inject venom into their dipteran hosts just prior to laying eggs on the host's outer integument. The parasitoid larvae are ectoparasitoids because they feed on their hosts within the puparium, but do not enter the host body. We investigated the influence of N. vitripennis venom on the gene expression profile of hemocytes of their hosts, pupae of the housefly, Musca domestica. We prepared venom by isolating venom glands and treated experimental host pupae with venom. We used suppression subtractive hybridization (SSH) to determine the influence of venom on hemocyte gene expression. At 1 h post treatment, we recorded decreases in transcript levels of 133 EST clones derived from forward a subtractive library of host hemocytes and upregulation in transcript levels of 111 EST clones from the reverse library. These genes are related to immune and stress response, cytoskeleton, cell cycle and apoptosis, metabolism, transport, and transcription/translation regulation. We verified the reliability of our data with reverse transcription quantitative real-time PCR analysis of randomly selected genes, and with assays of enzyme activities. These analyses showed that the expression level of all selected genes were downregulated after venom treatment. Outcomes of our experiments support the hypothesis that N. vitripennis venom influences the gene expression in host hemocytes. We conclude that the actions of venom on host gene expression influence host biology in ways that benefit the development and emergence of the next generation of parasitoids.