Dissecting the genetic architecture of a stepwise infection process

How a host fights infection depends on an ordered sequence of steps, beginning with attempts to prevent a pathogen from establishing an infection, through to steps that mitigate a pathogen’s control of host resources, or minimising the damage caused during infection. Yet empirically characterising the genetic basis of these steps remains challenging. Although each step is likely to have a unique genetic and environmental signature, and may, therefore, respond to selection in a specific way, events that occur earlier in the infection process can mask or overwhelm the contributions of subsequent steps. In this study, we dissect the genetic architecture of a stepwise infection process using a quantitative trait loci (QTL) mapping approach. We control for variation at the first line of defence against a bacterial pathogen and expose downstream genetic variability related to the host’s ability to mitigate the damage pathogens cause. In our model, the water-flea Daphnia magna, we found a sing...