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Regulation of Wolbachia density within Drosophila simulans Open Access


Other title
Drosophila simulans
WO phage
cytoplasmic incompatibility
Type of item
Degree grantor
University of Alberta
Author or creator
Haukedal, Jennifer Ann
Supervisor and department
Keddie, Andrew (Department of Biological Sciences)
Harris, Harriet (Department of Biological Sciences)
Examining committee member and department
Fallon, Ann (Department of Entomology)
Evans, David (Department of Medical Microbiology and Immunology)
Simmonds, Andrew (Department of Cell Biology)
Department of Biological Sciences
Physiology, Cell and Developmental Biology
Date accepted
Graduation date
Doctor of Philosophy
Degree level
The endosymbiont Wolbachia pipientis is a Gram negative alpha proteobacterium and is found in a wide range of insects, spiders and mites, nematodes, and crustaceans. Wolbachia is responsible for several reproductive manipulations within its host, most notably, cytoplasmic incompatibility (CI). CI is a form of conditional male sterility by which infected males can only successfully mate with females infected with the same Wolbachia strain. Wolbachia density within developing sperm has been implicated in determination of the penetrence of CI within populations. To this end, this study examines two distinct factors that may regulate Wolbachia density in Drosophila simulans: replication of the WO phage and oxidative stress imbalance between host and symbiont. The replication of the WO phage, a temperate bacteriophage found within the wRi genome has previously been correlated with Wolbachia density and CI. In D. simulans, only one of the three phage genomes is undergoing replication, WORiC, and replication of WORiC does not appear to correlate with Wolbachia density. D. simulans infected with wRi (DSR) contains a higher amount of reactive oxygen species (ROS) when compared with uninfected flies (DSRT). The exogenous feeding of the antioxidant compounds glutathione and ascorbic acid increases Wolbachia density three fold in males, females, and their testes and ovaries. This increase in density is not attributed to amino acid scavenging or an increase in fly fitness. In developing sperm, the ROS-producing enzyme NADPH oxidase is found exclusively in the nuclear region and does not appear to differ between DSR and DSRT. Dual oxidase, another member of the NADPH oxidase family, however, was found in close association with Wolbachia-containing vesicles. In vitro, the NADPH oxidase inhibitors VAS2870, apocynin, and DPI had varying abilities to inhibit the amount of total ROS found in DSR and DSRT; homogenates from DSR were more susceptible to apocynin and DPI than DSRT. Exogenous feeding of apocynin and VAS2870, however, did not change Wolbachia density in young males. Unlike other Wolbachia-host systems, the activity of the WO phage in wRi does not appear to be a factor that is regulating Wolbachia density. This may be due to a very low level of replicating phage and a relatively high Wolbachia titer. A redox-dependent mechanism of regulation of Wolbachia density is more likely and dual oxidase is a strong candidate as the key component of this regulation.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
Biliske, J. a, Batista, P.D., Grant, C.L., Harris, H.L., 2011. The bacteriophage WORiC is the active phage element in wRi of Drosophila simulans and represents a conserved class of WO phages. BMC Microbiology 11, 251.

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