Affiliations: 1) Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL; 2) University of Florida Genetics Institute, University of Florida, Gainesville, FL; 3) Department of Biological Sciences, Auburn University, Auburn, AL; 4) Department of Biological Sciences, North Dakota State University, Fargo, ND; 5) Department of Biological Sciences, University of Southern California, Los Angeles, CA
Keywords: d. evolution of gene expression; j. epigenetics
Antagonistic coevolution between the sexes should drive the faster evolution of reproductive-related characteristics, including sexually dimorphic morphology and behavior. Interestingly, the closely related human commensal species, D. melanogaster and D. simulans, have diverged in sexual dimorphic behaviors. These behaviors are potential targets of sex antagonism. While trends of sex-biased expression tend to be tissue-specific in Drosophila, there has been more male-biased expression observed in head and brain tissues, with an enrichment of male-biased genes on the X chromosome. However, the relationship between sex-biased expression and chromatin in the context of sex dimorphism and evolution is not well understood. Here we show evidence for faster evolution of the X for both chromatin and gene expression in D. melanogaster and D. simulans, with underlying sex-biased genes conserved between the species. We observe more sex-biased expression, specifically male-biased expression, on the X compared to the autosomes in both species. Additionally, male open chromatin marks are enriched on the X. Open chromatin marks in each of the sexes are associated (70% concordant) with sex-biased expression in the corresponding sex. These results indicate chromatin plays a role in sex dimorphism of expression and evolution.