Mank Judith E, Ellegren Hans
Department of Zoology, University of Oxford, Oxford, United Kingdom.
Evolution. 2009 Jun;63(6):1464-72. doi: 10.1111/j.1558-5646.2009.00618.x. Epub 2009 Jan 14.
Evolutionary theory predicts that sexually antagonistic loci will be preferentially sex-linked, and this association can be empirically testes with data on sex-biased gene expression with the assumption that sex-biased gene expression represents the resolution of past sexual antagonism. However, incomplete dosage compensating mechanisms and meiotic sex chromosome inactivation have hampered efforts to connect expression data to theoretical predictions regarding the genomic distribution of sexually antagonistic loci in a variety of animals. Here we use data on the underlying regulatory mechanism that produce expression sex-bias to test the genomic distribution of sexually antagonistic genes in chicken. Using this approach, which is free from problems associated with the lack of dosage compensation in birds, we show that female-detriment genes are significantly overrepresented on the Z chromosome, and female-benefit genes underrepresented. By contrast, male-effect genes show no over- or underrepresentation on the Z chromosome. These data are consistent with a dominant mode of inheritance for sexually antagonistic genes, in which male-benefit coding mutations are more likely to be fixed on the Z due to stronger male-specific selective pressures. After fixation of male-benefit alleles, regulatory changes in females evolve to minimize antagonism by reducing female expression.
进化理论预测，性拮抗基因座将优先与性染色体连锁，并且在假定性偏向基因表达代表过去性拮抗作用的解决方式的情况下，这种关联可以通过性偏向基因表达的数据进行实证检验。然而，不完全的剂量补偿机制和减数分裂性染色体失活阻碍了将表达数据与关于各种动物中性拮抗基因座的基因组分布的理论预测联系起来的努力。在这里，我们利用产生表达性偏向的潜在调控机制的数据来检验鸡中性拮抗基因的基因组分布。使用这种方法，避免了与鸟类缺乏剂量补偿相关的问题，我们发现对雌性有害的基因在Z染色体上显著富集，而对雌性有益的基因则不足。相比之下，对雄性有影响的基因在Z染色体上没有过度或不足的情况。这些数据与性拮抗基因的显性遗传模式一致，即由于更强的雄性特异性选择压力，对雄性有益的编码突变更有可能在Z染色体上固定下来。在对雄性有益的等位基因固定之后，雌性的调控变化通过降低雌性表达来进化，以尽量减少拮抗作用。
