Regulation of Wolbachia density within Drosophila simulans

• Author / Creator

  Haukedal, Jennifer Ann

• 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.

• Subjects / Keywords

  • Cytoplasmic incompatibility
  • WO phage
  • Drosophila simulans
  • Wolbachia

• Graduation date

  Fall 2013

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3XS5JR4G

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.