Cis-regulatory variation in relation to sex and sexual dimorphism in Drosophila melanogaster

Abstract

Much of sexual dimorphism is likely due to sex-biased gene expression, which results from differential regulation of a genome that is largely shared between males and females. Here we use allele-specific expression to explore cis-regulatory variation in Drosophila melanogaster in relation to sex. We develop a Bayesian framework to infer the transcriptome-wide joint distribution of cis-regulatory effects across the sexes. We use this approach to quantify transcriptome-wide sex differences in cis-regulatory effects as well as examine patterns of cis-regulatory variation with respect to two other levels of variation in sexual dimorphism: (i) across genes varying in their degree of sex-biased expression, and (ii) among tissues that vary in their degree of dimorphism (e.g., relatively low dimorphism in heads vs high dimorphism in gonads). We uncover evidence of widespread cis-regulatory variation in all tissues examined, with female-biased genes being especially enriched for this variation. A sizeable proportion of cis-regulatory variation is inferred to have sex-specific effects, with sex-dependent cis effects being much more frequent in gonads than in heads. Finally, we detect some genes with reversed allelic imbalance between the sexes. Such variants could provide a mechanism for sex-specific dominance reversals, a phenomenon important for sexually antagonistic balancing selection.