Differential expression of immune defences is associated with specific host-parasite interactions in insects

Abstract

Recent ecological studies in invertebrates show that the outcome of an infection is dependent on the specific pairing of host and parasite. Such specificity contrasts the long-held view that invertebrate innate immunity depends on a broad-spectrum recognition system. An important question is whether this specificity is due to the immune response rather than some other interplay between host and parasite genotypes. By measuring the expression of putative bumblebee homologues of antimicrobial peptides in response to infection by their gut trypanosome Crithidia bombi, we demonstrate that expression differences are associated with the specific interactions.

Figure 1. Relative expression of the antimicrobial peptides.

Expression levels of (A) hymenoptaecin (values zero skew log transformed as: ln (fold change in hymenoptaecin expression – 0.1952191) normalised to a noninfected control), (B) abaecin (box-cox transformed: Fold change^−1.0302212/−0.0302212, normalised to a noninfected control) and (C) defensin (box-cox transformed: Fold change^−0.955746/0.044254, normalised to a noninfected control) across four B.terrestris colonies (host lines) in response to four different Crithidia isolates (see in-graph legend). Points represent the means and error bars represent the standard errors.