Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada.
Mol Biol Evol. 2023 May 2;40(5). doi: 10.1093/molbev/msad091.
Phenotypic sexual dimorphism can be mediated by sex differences in gene expression. We examine two forms of sexual dimorphism in gene expression in Drosophila melanogaster: 1) sex-biased gene expression (SBGE) in which the sexes differ in the amount a gene is expressed and 2) sexual dimorphism in isoform usage, that is, sex-specific splicing (SSS). In whole body (but not the head) expression, we find a negative association between SBGE and SSS, possibly suggesting that these are alternate routes to resolving sexual antagonistic selection. Next, we evaluate whether expression dimorphism contributes to the heterogeneity among genes in rmf, the intersexual genetic correlation in body expression that constrains the extent to which a gene's expression can evolve independently between the sexes. We find lower rmf values for genes with than without SSS. We find higher rmf values for male- than female-biased genes (except genes with extreme male bias), even though male-biased genes are known to have greater evolutionary divergence in expression. Finally, we examine population genetic patterns in relation to SBGE and SSS because genes with expression dimorphism have likely experienced a history of sex differences in selection. SSS is associated with reduced values of Tajima's D and elevated direction of selection (DoS) values, suggestive of higher rates of adaptive evolution. Though DoS is highly elevated for genes with extreme male bias, DoS otherwise tends to decline from female-biased to unbiased to male-biased genes. Collectively, the results indicate that SBGE and SSS are differentially distributed across the genome and are associated with different forms of selection.
表型性别二态性可以通过基因表达的性别差异来介导。我们研究了果蝇中两种形式的基因表达性别二态性：1）性别偏倚基因表达（SBGE），其中雌雄在基因表达量上存在差异，2）同工型使用的性别二态性，即性别特异性剪接（SSS）。在整体（但不是头部）表达中，我们发现 SBGE 和 SSS 之间存在负相关，这可能表明它们是解决性拮抗选择的替代途径。接下来，我们评估表达二态性是否有助于解决 rmf 中基因之间的异质性，rmf 是两性间遗传相关性在体表达，限制了一个基因的表达在两性之间独立进化的程度。我们发现，与没有 SSS 的基因相比，具有 SSS 的基因的 rmf 值较低。与雌性偏倚基因相比，雄性偏倚基因的 rmf 值较高（除了具有极端雄性偏倚的基因），尽管已知雄性偏倚基因在表达上具有更大的进化差异。最后，我们研究了与 SBGE 和 SSS 相关的种群遗传模式，因为具有表达二态性的基因可能经历了选择性别差异的历史。SSS 与 Tajima 的 D 值降低和选择方向（DoS）值升高相关，提示适应性进化的速度更高。尽管具有极端雄性偏倚的基因的 DoS 值非常高，但 DoS 值通常从雌性偏倚基因下降到无偏倚基因，再到雄性偏倚基因。总的来说，这些结果表明，SBGE 和 SSS 在基因组中分布不同，并且与不同形式的选择相关。
