Résumé
Because of their role as vectors of diseases, the evolution of insecticide
resistance in mosquitoes has been intensively investigated. Insecticide
resistance is associated to a wide range of pleiotropic effects on several
key life history traits of mosquitoes such as longevity and behavior.
However, despite its potential implications in pathogen transmission, the
effects of insecticide resistance on mosquito immunity have received
little, if any, attention. Here, we investigate the impact of insecticide
resistance in Culex pipiens, an epidemiologically important vector of a
wide array of pathogens. Using both isogenic laboratory strains and
field-caught mosquitoes, we investigate the impact of two main insecticide
resistance mechanisms (metabolic detoxification and target site
modification) on the relative transcription of several genes involved in
the immune response to pathogens, at both their constitutive and inducible
levels. Our results show a discrepancy between the isogenic laboratory
lines and field collected mosquitoes: while in the isogenic strains
insecticide resistant mosquitoes show a drastic increase in immune gene
expression, no such effect appears in the field. We speculate on the
different mechanisms that may underlie this discrepancy, and discuss the
risks of making inferences on the pleiotropic effects of insecticide
resistant genes by using laboratory-selected insecticide resistant lines.