Wolbachia variants differentially rescue the fertility of a bag-of-marbles mutant in Drosophila melanogaster

The vertically-transmitted endosymbiotic bacterium Wolbachia pipientis infects a large proportion of arthropod species by manipulating their reproductive biology in order to increase its transmission. In Drosophila melanogaster, effects of Wolbachia pipientis (wMel) infection on host fitness can range from detrimental to beneficial. Previous work showed that wMel infection rescues fertility defects in mutants of bag-of-marbles (bam), a key switch for germline stem cell differentiation that shows patterns of episodic adaptive evolution across the Drosophila genus. wMel is therefore of key interest as a potential selective pressure on bam. The aim of this project was to further understand the co-evolutionary relationship between wMel and bam and determine whether fertility rescue of bam mutants by wMel varies due to wMel genotype. We examined female fertility and oocyte production of isogenic D. melanogaster bam mutants infected with 11 genetically distinct wMel variants over the course of 17 days. Subsequent analysis led to the result that wMel infection not only rescues fertility of bam mutants, but that the degree of rescue depends on the wMel variant. The highest rescue was due to infection by wMelCS-like variants, which typically have higher titer. Future steps include manipulating wMel titer using the wMelPop strain to directly investigate the relationship between titer and degree of bam rescue. This and future studies will further elucidate the co-evolutionary relationship between Drosophila melanogaster and Wolbachia pipientis.