Wolbachia neither induces nor suppresses transcripts encoding antimicrobial peptides

Wolbachia are intracellular maternally inherited microorganisms that are as sociated with reproductive abnormalities such as cytoplasmic incompatibilit y (Cl), feminization and parthenogenesis in the various arthropod species t hey infect. Surveys indicate that these bacteria infect more than 16% of al l insect species as well as isopods, mites and nematodes, making Wolbachia one of the most ubiquitous parasites yet described. However, nothing is kno wn about the interactions of this bacterium with the host's immune system. We studied the expression of inducible antimicrobial markers in the adults of two Wolbachia infected insect species, Drosophila simulans and Aedes alb opictus. The lack of available immune markers in the mosquito species led u s to clone part of the defensin gene from this species, which was found to be very similar to the other mosquito defensins cloned from Anopheles gambi ae and Aedes aegypti. Comparisons of the expression pattern of the antibact erial markers between Wolbachia-infected and cured lines, and also between bacteria-challenged and unchallenged adults indicated that Wolbachia does n ot either constitutively induce or suppress the transcription of these anti bacterial genes. In addition, no difference in the transcription of these g enes was found between double and single Wolbachia-infected strains or betw een strains in which Wolbachia has different tissue tropisms.