Symbiotic associations with microbes are nearly ubiquitous across insects. Approximately half of all insects are infected with one such bacterium: Wolbachia. Wolbachia is passed from mother to offspring via the insect egg, and is of interest to insect management programs due to the bacterium’s ability to spread in insect populations and modify insect reproduction and physiology. However, we know relatively little about the mechanisms by which Wolbachia establishes infection in insects, alters their biology, and how this symbiosis in turn affects insect evolution. We use a range of genomic, molecular, and computational approaches to investigate insect-Wolbachia interactions. Some of the questions we are currently interested in include: (1) the genetic basis of Wolbachia-mediated changes in insect biology, (2) how Wolbachia regulate gene expression in response to host signals, (3) the mechanisms of establishing Wolbachia infections in new insect hosts, and (4) the genomic and evolutionary consequences of symbiosis with Wolbachia. Below are some of the systems we use to understand Wolbachia biology and evolution.
Across the Drosophila genus, there are numerous strains of Wolbachia that affect their fly hosts in various ways. Some harbor Wolbachia strains that cause sperm-egg incompatibilities. Other Wolbachia can make their host recalcitrant to secondary infections with RNA viruses, and are being transferred to mosquitoes for use in vector control programs. Certain Drosophila species host multiple co-infecting Wolbachia. The diversity of host-Wolbachia interactions in this group coupled with genetic tools available for Drosophila melanogaster make this an excellent system study fundamental aspects of Wolbachia-host interactions.
Many species of parasitoid wasps harbor Wolbachia strains that convert them to a form of asexual reproduction: parthenogenesis. Sometimes, this switch to asexuality can be permanent: wasps rely upon Wolbachia for the continued production of females. We are interested in the mechanistic basis of parthenogenesis induction, and the evolutionary consequences of Wolbachia-mediated loss of sex. We use wasps in the genera Trichogramma and Leptopilina to study insect-parasitoid, parasitioid-Wolbachia, and insect-parasitoid-Wolbachia interactions.
Insect cell culture systems allow us to easily move Wolbachia between host contexts, visualize the localization of the bacteria, and track the progress of infection. There is a suite of molecular tools available for insect cells lines that facilitate genetic, molecular, and microscopic studies of the host-Wolbachia relationship.