Fig 3. Dosage compensation of neo-X chromosomes.

(A) We profiled gene expression in Drosophila heads using RNA-seq, and male/female gene expression ratios are shown for each chromosome for D. robusta (top) and D. melanica (bottom). X-linked genes (blue boxes) are expressed at roughly equal levels in both males and females, suggesting that both the ancestral and neo-X chromosomes are fully dosage compensated. Underlying data can be found in S3 Data. (B) Identification of roX2. In other Drosophila species, the male-specific noncoding roX2 transcript is located between the protein-coding genes e(y)2 and ari-1. We identified the roX2 transcript in D. melanica and D. robusta by visualizing RNA-seq data from heads across the e(y)2–ari-1 genomic region. The gray box indicates the location of roX2, which shows abundant expression only in males. RNA-seq, RNA sequencing.