Sex-Biased Gene Expression and Sexual Dimorphism

Sex-biased gene expression denotes differential transcriptional activity between males and females, underpinning the development of sex-specific traits and forms of sexual dimorphism. Such divergence arises through a combination of genetic and epigenetic mechanisms, including sex chromosome differentiation, hormone-mediated regulation and cis-regulatory variation. Dosage compensation often mitigates imbalances in sex chromosome gene dose, while autosomal loci may evolve sex-biased regulation to resolve intralocus sexual conflict. Across taxa—from invertebrates and plants to vertebrates—sex-biased genes contribute to morphological, behavioural and physiological differences, playing central roles in reproduction, environmental adaptation and the epidemiology of sex-specific diseases. Evolutionary forces acting on these genes, notably positive selection, purifying selection and balancing selection, shape the rates of sequence divergence, maintain genetic diversity and influence the persistence of sexually antagonistic variation. Insights into these processes have practical applications in conservation biology, pest management and precision medicine, where sex-specific genetic architectures inform management strategies and therapeutic interventions.

Research from Nature Portfolio

New high-quality genome assemblies for two firefly species exhibiting contrasting degrees of sexual dimorphism reveal full dosage compensation of the single male X-chromosome and exceptional conservation of X-chromosome synteny over 180 million years. Analyses demonstrate that sex-biased genes are predominantly autosomal, show varying levels of expression conservation across tissues, and harbour elevated nucleotide diversity in intronic regions, implicating sexual selection in maintaining heterozygosity. In seed beetles, comprehensive population resequencing coupled with transcriptome assembly uncovers genomic signatures of sexual conflict. Sex-biased genes display increased genetic diversity under relaxed purifying selection, while balancing selection maintains polymorphism in weakly female-biased loci. These findings connect life-history traits known to experience sexually antagonistic selection with concrete genomic footprints, illuminating mechanisms by which conflict drives and constrains sexual dimorphism.

Sex-Biased Gene Expression and Sexual Dimorphism publication trend

The graph below shows the total number of articles in sex-biased gene expression and sexual dimorphism across all publications each year (not limited to Nature Index journals).

Technical terms

Sex-biased gene expression: Differential gene transcription levels between males and females.

Sexual dimorphism: Phenotypic differences between the sexes arising from genetic and regulatory variation.

Dosage compensation: Mechanism balancing gene expression between sex chromosomes and autosomes.

Heterogamety: Chromosomal system (e.g. XX/XY or ZW/ZZ) that determines sex.

Sexual antagonism: Conflicting selection pressures on the same gene in males versus females.

Purifying selection: Evolutionary force removing deleterious alleles from a population.

Balancing selection: Evolutionary force maintaining multiple alleles at a locus within a population.

References

1. Sex-linked gene traffic underlies the acquisition of sexually dimorphic UV color vision in Heliconius butterflies. Proceedings of the National Academy of Sciences of the United States of America (2023).
2. Evolutionary dynamics of sex‐biased gene expression in a young XY system: insights from the brown alga genus Fucus. New Phytologist (2023).
3. Positive selection and relaxed purifying selection contribute to rapid evolution of male-biased genes in a dioecious flowering plant. eLife (2024).
4. Two novel genomes of fireflies with different degrees of sexual dimorphism reveal insights into sex-biased gene expression and dosage compensation. Communications Biology (2024).
5. Male‐biased gene expression resolves sexual conflict through the evolution of sex‐specific genetic architecture. Evolution Letters (2018).
6. The evolution of sex differences in disease. Biology of Sex Differences (2015).