Complex environmental drivers of immunity and resistance in malaria mosquitoes

Considerable research effort has been directed at understanding the genetic and molecular basis of mosquito innate immune mechanisms. Whether environmental factors interact with these mechanisms to shape overall resistance remains largely unexplored. Here we examine how changes in mean ambient temperature, diurnal temperature fluctuation, and time of day of infection affected the immunity and resistance of Anopheles stephensi to infection with Escherichia coli. We used quantitative PCR to estimate the gene expression of three immune genes in response to challenge with heat-killed Escherichia coli. We also infected mosquitoes with live E. coli and ran bacterial survival assays to quantify host resistance. Both mosquito immune parameters and resistance were directly affected by mean temperature, diurnal temperature fluctuation, and time of day of infection. Furthermore there was a suite of complex 2- and 3-way interactions yielding idiosyncratic phenotypic variation under different en...