pickpocket 6 as a genetic target of sexual selection

Identifying genes under sexual selection is challenging, especially those showing antagonistic effects between the sexes. We have developed knockout mutants of Pickpocket 6 (ppk6) in Drosophila pseudoobscura after it was implicated as a potential target of sexual selection following an experimental evolution study. Members of this gene family influence mating behaviour in D. melanogaster, but no studies have previously been reported in D. pseudoobscura. Here we show that knockout of ppk6 (ppk6-) influences sperm competition, fitness, lifetime reproductive success, and mating behaviour. ppk6- males were more successful at securing matings, showed significantly higher sperm defence and had greater lifetime reproductive success, even when outnumbered, compared to wild type (WT) males, suggesting that functional WT ppk6 alleles may be deleterious for males, i.e. antagonistic, when faced with high competition for mates. ppk6- females had a significantly higher remating rate, which may be adaptive to females in the context of “trading up” to a fitter partner, and processed sperm from multiple matings differently to WT females. Transcriptomic analyses were used to infer functions associated with ppk6; we found that ppk6- males showed significant enrichment for genes relating to ribosomal proteins which are associated with seminal fluid protein production, whereas mated ppk6- females were enriched for genes relating to pheromone perception and neural function. Overall, our results implicate ppk6 as a possible candidate of intralocus sexual antagonism and a crucial component of multiple reproductive behaviours.