PT  - JOURNAL ARTICLE
AU  - Ana Llopart
AU  - Evgeny Brud
AU  - Nikale Pettie
AU  - Josep M. Comeron
TI  - Support for the dominance theory in <em>Drosophila</em> transcriptomes
AID  - 10.1101/321455
DP  - 2018 Jan 01
TA  - bioRxiv
PG  - 321455
4099  - http://biorxiv.org/content/early/2018/05/14/321455.short
4100  - http://biorxiv.org/content/early/2018/05/14/321455.full
AB  - Interactions among divergent elements of transcriptional networks from different species can lead to misexpression in hybrids through regulatory incompatibilities, some with the potential to generate sterility. Genes with male-biased expression tend to be overrepresented among genes misexpressed in hybrid males. While the possible contribution of faster-male evolution to this misexpression has been explored, the role of the hemizygous X chromosome (i.e., the dominance theory for transcriptomes) remains yet to be determined. Here we study genome-wide patterns of gene expression in females and males of Drosophila yakuba and D. santomea and their hybrids. We used attached-X stocks to specifically test the dominance theory, and we uncovered a significant contribution of recessive alleles on the X chromosome to hybrid misexpression. Our analysis of gene expression patterns suggests that there is a contribution of weakly deleterious regulatory mutations to gene expression divergence in the sex towards which the expression is biased. In the opposite sex (e.g., genes with female-biased expression analyzed in male transcriptomes), we detect stronger selective constraints on gene expression divergence. Although genes with high degree of male-biased expression show a clear signal of faster-X evolution for gene expression divergence, we also detected slower-X evolution of gene expression in other gene classes (e.g. female-biased genes) that is mediated by significant decreases of cis- and trans-regulatory divergence. The distinct behavior of X-linked genes with high degree of male-biased expression is consistent with these genes experiencing a higher incidence of positively selected regulatory mutations than their autosomal counterparts. We propose that both dominance theory and faster-X evolution of gene expression may be major contributors to hybrid misexpression and possibly the large X-effect in these species.