Extensive chromosomal insertions of Wolbachia genes noted in the Glossina genome.

Wolbachia is an obligatory intracellular maternally transmitted bacterium that infects many arthropod and filarial nematode species. Wolbachia infections result in a number of reproductive alterations in the host, including parthenogenesis induction, male killing, feminization of genetic males, and cytoplasmic incompatibility (CI). Wolbachia has prompted research regarding its potential for control of agricultural and medical disease vectors, including Glossina spp., which transmits African trypanosomes, the causative agents of sleeping sickness in humans and nagana in animals. Several recent studies reported that Wolbachia genes have been horizontally transferred to host chromosomes including in Glossina morsitans morsitans. In our study we present the localization of three Wolbachia insertions on G. m. morsitans mitotic chromosomes. From the in situ hybridization results, it appears that the three Wolbachia sequences 16S rRNA, fbpA, and wsp consistently show a biased location on X, Y and B supernumerary chromosomes. Southern-blot analysis were performed to determine the number of chromosomal insertions, using genomic DNA from tetracycline treated G. m. morsitans females and untreated normal females and males. Both the Southern blot and in situ hybridization analyses provide evidence that Wolbachia fragments are inserted into the chromosome, supporting the in silico data. The chromosomal location of the Wolbachia insertions may reflect the common evolutionary origin of the sex and B chromosomes. It remains to be assessed whether the the inserted sequences play any functional role(s) in host physiology.