Wolbachia infection at least partially rescues the fertility and ovary defects of several new Drosophila melanogaster bag of marbles protein-coding mutants

The D. melanogaster protein coding gene bag of marbles (bam) plays a key role in early male and female reproduction by forming complexes with partner proteins to promote differentiation in gametogenesis. Like another germline gene, Sex lethal, bam genetically interacts with the endosymbiont Wolbachia, as Wolbachia rescues the reduced fertility of a bam hypomorphic mutant. Here, we explored the specificity of the bam-Wolbachia interaction by generating 22 new bam mutants, with ten mutants displaying fertility defects. Nine of these mutants trend towards rescue by the wMel Wolbachia variant, with eight statistically significant at the fertility and/or cytological level. In some cases, fertility was increased a striking 20-fold. There is no specificity between the rescue and the known binding regions of bam, suggesting wMel does not interact with one singular bam partner to rescue the reproductive phenotype. We further tested if wMel interacts with bam in a non-specific way, by increasing bam transcript levels or acting upstream in germline stem cells. A fertility assessment of a bam RNAi knockdown mutant reveals that wMel rescue is specific to functionally mutant bam alleles and we find no obvious evidence of wMel interaction with germline stem cells in bam mutants.