The Epigenome of Evolving Drosophila Neo-Sex Chromosomes: Dosage Compensation and Heterochromatin Formation
Figure 3
Heterochromatin formation on the neo-Y of D. miranda.
(A) Enrichment profile of H3K9me2 on the D. miranda neo-sex chromosomes. Intensity ratios are plotted for H3K9me2 (y-axis) relative to chromosomal position (x-axis), for protein-coding genes and their flanking regions along the neo-sex chromosomes. (B) Genome Browser screen capture of a 50 kb region on the neo-sex chromosomes showing intensity ratios for histone marks (H3K9me2, in black) and read coverage depth for RNA-seq data (in red) for the neo-Y and neo-X chromosomes in male third instar larvae. Gene models for potentially functional neo-Y genes are in blue, and for non-functional neo-Y genes in black. (C) TE accumulation on the neo-Y relative to the neo-X, versus H3K9me2 binding along the neo-Y. The ratios of neo-Y repeat-linked read numbers versus neo-X repeat-linked reads were pooled into four bins of equal size, as a reflection of the degree of neo-Y specific repeat accumulation. The boxplots show the neo-Y specific H3K9me2 binding ratios within each bin, and genes without neo-Y specific repeat enrichments show a significantly lower H3K9me2 binding (Wilcoxon one tailed test: p-value<0.05) than others. The number of asterisks reflects the significance level. *, p-value<0.05; **, p-value<0.01; ***, p-value<0.0001.