| Cytoplasmic incompatibility (CI), a name given to the phenomenon by Laven (1959), results in high levels of egg mortality. CI arises when females of one strain are mated to males of another strain (usually from geographically separated regions): such crosses yield few or no progeny. CI has been linked to the presence of a Rickettsia-like endosymbiont inhabiting the gonads of infected animals. Though originally discovered in mosquitoes, CI has now been observed in a diverse array of insects including mosquitoes (Aedes group), beetles (Tribolium confusum), moths (Ephestia cautella), wasps (Nasonia vitripennis), and flies (Drosophila simulans). The cellular and molecular mechanisms of CI are not known.;To study mechanisms for the transmission of CI, egg cytoplasm from a naturally infected strain of Drosophila simulans from Riverside, CA. (DSR) was microinjected into a strain treated with the antibiotic tetracycline that removed the symbiont (designated DSR;The transinfected strains were assayed for the expression of CI. Interestingly, cytoplasmic transfers from DSR into DSR;To determine the effect of host factors on the expression of CI in the transinfected DM lines, a CI selection assay was used to select individual females expressing high levels of CI. Following eight generations of selection, DM lines expressing high levels of CI were attained. Further analysis provided evidence for the link between the level of CI and the level of infection in these populations. |
