Transinfection of Wolbachia in the Mediterranean Flour Moth, Ephestia kuehniella, by Embryonic Microinjection

Wolbachia are maternally transmitted intracellular bacteria found in many arthropod species. They cause a reproductive incompatibility called cytoplasmic incompatibility (CI) in several hosts, including the Mediterranean flour moth, Ephestia kuehniella. Two strains of E. kuehniella, one from Yokohama city and the other from Tsuchiura city, express different levels of CI: the Yokohama strain expresses CI at a higher level than the Tsuchiura strain. In order to determine whether the difference of CI levels depends on Wolbachia or the host, we performed transinfection experiments in E. kuehniella by means of embryonic microinjection, and successfully transferred Wolbachia carried by the Yokohama strain into the Tsuchiura strain, from which the original Wolbachia had been removed by tetracycline treatment. The resulting transinfected strain expressed CI at a level near that of the Yokohama strain, suggesting that, in these strains of E. kuehniella, the level of CI is determined by Wolbachia rather than by the host.