Biology subjects

Liu, M. J.

Publications and source records attributed to Liu, M. J..

3 recordsLinked to original sources

bioRxiv2026

Sex-biased expression in whole bodies, tissues and cell-types: patterns across and within levels

Whole body transcriptomes have been widely used to study the evolution of sex-biased genes, yet it remains unclear what whole body sex bias represents biologically. Using the FlyAtlas2 and Fly Cell Atlas datasets from Drosophila melanogaster, we show that whole body sex bias emerges from both sex-biased regulation within smaller biological units and how genes are expressed these across units, the latter indicating the contribution of compositional differences to whole body sex bias. Despite these compositional effects, the direction of whole body sex bias is generally consistent with that observed across most tissues and cell-types because sex bias tends to be positively correlated among tissues and among cell-types. Genes which display sex-biased expression across multiple tissues/cell-types typically exhibit the greatest magnitude of sex bias in reproductive tissues/cell-types, consistent with widespread pleiotropic spillover from reproductive components. Among genes lacking gonadal sex bias, the magnitude of sex-biased expression is often greatest in tissues where genes are less highly expressed, further suggesting the role of pleiotropy. In revisiting the evolutionary patterns with respect to tissue level sex bias, we find that elevated rates of adaptive evolution among gonad-expressed sex-biased genes are better explained by their greater expression localization in the reproductive tissues, rather than by their sex bias itself. However, among genes not expressed in the gonads, strong male-biased expression in non-gonadal tissues remains independently associated with increased adaptive evolution. Together, our results show that whole body sex bias is a meaningful summary of broad-scale sex-biased expression though may obscure finer-scale evolutionary signals.

evolutionary biology↗

bioRxiv2026

Local Adaptation to the Sex Environment: Reciprocal Sex-Limited Selection in Different Thermal Regimes

The shared genome prevents each sex from independently responding to the selection experienced by that sex. We used experimental evolution in Drosophila melanogaster with separate pools of Chromosome 3s for males (male-limited chromosomes) and females (female-limited chromosomes) for 15 generations. Viewing each sex as a separate environment, we performed a reciprocal transplant between the sexes to quantify the strength of local adaptation to each sex environment. Each chromosome type was more beneficial in the sex it had been selected for (i.e., local adaptation to sex). Because it has been postulated that sex differences in selection may depend on how well adapted a population is to the abiotic environment, we performed experimental evolution at two thermal regimes: one benign temperature to which the populations were well-adapted and one novel temperature. Female-specific adaptation was stronger at the benign temperature whereas male-specific adaptation was stronger in the novel temperature. Within chromosome pools, male and female fitness were more positively correlated in the novel compared to the benign temperature. Though males carrying male-limited chromosomes were typically more fit than males carrying female-limited chromosomes, they were also more harmful to their female mating partners.

evolutionary biology↗

bioRxiv2024

Expression divergence in response to sex-biased selection

It remains debated whether greater degrees of sexual dimorphism would evolve if not for intersexual genetic constraints. Here we used experimental evolution to partially break the intersexual genetic constraint in Drosophila melanogaster to investigate the effects of a shared gene pool on the evolution of sexual dimorphism in gene expression. In six replicate populations of 1000 flies, a dominant marker (DsRed) was used to force a "Red" pool of genetically variable Chromosome 2 copies through exclusive father-to-son inheritance, while a complimentary pool of "NonRed" chromosomes was inherited primarily from mothers to daughters. After 100 generations, we demonstrated the effect of Red male-limited chromosomes in increasing male mating success. Differentially expressed genes between flies with and without Red chromosomes had on average higher intersexual genetic correlations (rMF), as expected if such correlations represent a constraint to sex-specific adaptation under normal inheritance. If conflict hinders the evolution of further dimorphism, the transcriptomes of male-selected Red chromosomes were predicted to evolve to be "masculinized" relative to female-selected NonRed chromosomes. Consistent with this, splicing patterns in Red males (but not Red females) were masculinized relative to NonRed males. Contrastingly, gene expression levels were largely feminized in Red flies of both sexes compared to NonRed. We discuss alternative forms of intralocus sexual conflict that may explain these patterns.

evolutionary biology↗