Phenotypic differences between males and females (sexual dimorphism) are a major source of intra-specific variation. However, the majority of sexually dimorphic traits are assumed to arise from differences in expression for genes present in both sexes. Sex-biased genes have shown to exhibit accelerated rates of evolution in a wide array of species, yet the cause of this remains enigmatic. Recently, the research team led by Prof. HE Shunping from Institute of Hydrobiology, Chinese Academy of Sciences (IHB) revealed that both male-biased and female-biased genes evolve faster in fish genomes.   

They firstly identified sex-biased genes in zebrafish genome using RNA-seq data and found that almost 30% of protein-coding genes in zebrafish showed sex-biased expression. Subsequently, they found that both male-biased and female-biased genes evolve faster in zebrafish and stickleback genomes. In order to differentiate between adaptive and non-adaptive causes, they also tested for codon usage bias and signatures of different selective regimes in their sequence data and found that both male-biased and female-biased genes show signatures consistent with adaptive evolution.   

This study is the first report that both male-biased and female-biased genes evolve faster in fish genomes. This research was performed by Dr. YANG Liandong, and the corresponding author was Prof. HE Shunping. This work was supported by the China Scholarship Council and the Strategic Priority Research Program of the Chinese Academy of Sciences. The paper entitled “Both male-biased and female-biased genes evolve faster in fish genomes” has been published in the journal Genome Biology and Evolution.  

Figure: Both male-biased and female-biased genes evolve faster in zebrafish genome (Image by IHB)