Evolution and genetics of accessory gland transcriptome divergence betweenDrosophila melanogasterand D.simulans

Abstract

ABSTRACTStudies of allele-specific expression in interspecific hybrids have provided important insights into gene-regulatory divergence and hybrid incompatibilities. Many such investigations in Drosophila have used transcriptome data from whole animals or gonads, however, regulatory divergence may vary widely among species, sex, and tissues. Thus, we lack sufficiently broad sampling of tissues to be confident about the general principles of regulatory divergence. Here we seek to fill some of these gaps in the literature by characterizing regulatory evolution and hybrid misexpression in a somatic male sex organ, the accessory gland, in F1 hybrids betweenDrosophila melanogasterandD. simulans.The accessory gland produces seminal fluid proteins, which play an important role in male and female fertility and may be subject to adaptive divergence due to male-male or male-female interactions. We find thattransdifferences are relatively more abundant thancis, in contrast to most of the interspecific hybrid literature, though large effect-sizetransdifferences are rare. Seminal fluid protein genes have significantly elevated levels of expression divergence and tend to be regulated through bothcisandtransdivergence. We find limited misexpression in this organ compared to other Drosophila studies. As in previous studies, male-biased genes are overrepresented among misexpressed genes and are much more likely to be underexpressed. ATAC-Seq data show that chromatin accessibility is correlated with expression differences among species and hybrid allele-specific expression. This work identifies unique regulatory evolution and hybrid misexpression properties of the accessory gland and suggests the importance of tissue-specific allele-specific expression studies.