Comparative immunogenomics

Insects are remarkably diverse (there are an estimated 1 million species), and across that diversity is also an unusual degree of immunological diversity. Until recently, relatively little was known about the presence or absence of immunological proteins across species. Recent full genome sequencing suggests that insects can be quite different in the makeup of their immune system, with some pathways being completely absent in some species, like pea aphids, or generally reduce, like in many social insects.

Schematic of some of the immune pathways in the pea aphid. Genes outlined in red are missing in pea aphids but found in most other insects

Bumblebees are commonly infected with a trypanosome gut parasite. This is best known from the buff-tailed bumblebee Bombus terrestris, which is infected by Crithidia bombi. I use quantitative PCR and RNA-seq to determine what is involved in bumblebee immunity to this parasite, and how individuals vary in their response.

The consequences of sex

Mating is an expensive activity, and the costs should be visible in reduced investment in other costly traits like growth. I’m studying how sex influences a variety of these traits in bumblebees and what it means in terms of disease resistance.

Pea aphids are missing many of the immune components that other insects have. I have been exploring how aphids respond to immune challenges. While much of their immune response to Gram-negative bacteria is missing, it’s unclear whether aphids have other ways of dealing with Gram-negative infection. For example, aphids could respond to infection with increased reproduction rather than investing in costly immunity or might have other ways to respond to infection. I have been studying whether we can detect the costs of responding to pathogens (with Ben Parker) and whether aphids alter their reproduction to immune challenge in aphids of different ages and bearing different symbiotic bacteria (with Dan Sok). Aphids are very well suited to studies of the costs of immunity because they are extremely tractable and we can monitor many of the important evolutionarily important characteristics such as onset of reproduction, lifetime reproduction and survivorship. Working with Gabriel Leventhal and Robert Dünner we’re now using a mix of models and experiments to assess the conditions where fecundity compensation is likely to to succeed. 

Responses to infection: fecundity compensation and the costs of immunity

Bumblebee immunological gene expression