Transvection regulates the sex-biased expression of a fly X-linked gene

Sexual dimorphism in animals results from sex-biased gene expression patterns. These patterns are controlled by genetic sex determination hierarchies that establish the sex of an individual. Here we show that the male-biased wing expression pattern of the Drosophila biarmipes gene yellow, located on the X chromosome, is independent of the fly sex determination hierarchy. Instead, we find that a regulatory interaction between yellow alleles on homologous chromosomes (a process known as transvection) silences the activity of a yellow enhancer functioning in the wing. Therefore, this enhancer can be active in males (XY) but not in females (XX). This transvection-dependent enhancer silencing requires the yellow intron and the chromatin architecture protein Mod(mdg4). Our results suggest that transvection can contribute more generally to the sex-biased expression of X-linked genes.

Automated summary

Sexual dimorphism in animals is a result of sex-biased gene expression patterns controlled by genetic sex determination. The study shows that male-biased wing expression of the Drosophila gene yellow is independent of sex determination hierarchy and involves a process called transvection. This transvection-dependent enhancer silencing is mediated by the yellow intron and chromatin architecture protein Mod(mdg4), potentially contributing to sex-biased expression of X-linked genes.