Meiotic double strand DNA breaks and spontaneous mutation in Drosophila melanogaster

The exchange of genetic material during meiosis requires the formation and repair of DNA double-strand breaks (DSBs), which may not be repaired with perfect fidelity. If meiotic exchange is mutagenic, this would add to the costs of sexual reproduction and affect patterns of genome evolution, but much of the evidence for this is indirect. In the fruit fly Drosophila melanogaster, it is possible to completely suppress endogenous DSBs while retaining normal fertility. We took advantage of this system to generate fly strains with and without a mutant allele of mei-P22, a gene that is essential for meiotic DSB formation, on a common genetic background. This allowed us to investigate the relationship between DSBs and genome-wide mutation patterns, using a mutation accumulation design to allow un-selected spontaneous mutations to be observed. Following 30 generations of mutation accumulation, we identified over 1800 mutations by whole-genome sequencing. The presence of meiotic DSBs had little effect on the rate and spectrum of point mutations. We found that mutations were more likely to occur in areas of the genome with higher rates of crossover recombination, regardless of whether meiotic DSBs were occurring. We also found that the rate of transposable element insertions across multiple TE families was substantially elevated in the group lacking meiotic DSBs, suggesting that host suppression of mobile genetic elements is closely associated with meiotic recombination mechanisms.