Biochemical and cell biological studies of cytoplasmic incompatibility in Drosophila
Boyle, Lee Ann
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Permalink
https://hdl.handle.net/2142/19010
Description
Title
Biochemical and cell biological studies of cytoplasmic incompatibility in Drosophila
Author(s)
Boyle, Lee Ann
Issue Date
1993
Doctoral Committee Chair(s)
Karr, Timothy L.
Department of Study
Cell & Developmental Biology
Discipline
Cell & Developmental Biology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Entomology
Cellular Biology
Language
eng
Abstract
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$\sb{\rm T}).$ Similar experiments were performed in a closely related species, D. melanogaster (DM). The resulting transinfected lines were found to be infected with Wolbachia using two independent assays; (1) DAPI fluorescence (which detects DNA in the symbiont), and (2) the polymerase chain reaction (PCR) using primers specific for the 16S rRNA gene of Wolbachia.
"The transinfected strains were assayed for the expression of CI. Interestingly, cytoplasmic transfers from DSR into DSR$\sb{\rm T}$ displayed significant levels of CI while transfers from DSR into DM failed to exhibit any significant expression of CI. To determine the nature of the differences between these two strains, a quantitative confocal microscopic assay was used to determine that the number of Wolbachia in the transinfected DM strains were significantly lower than the DSR strains, suggesting that a ""threshold"" level of infection is necessary for the expression of CI."
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.
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