Evolutionary Biology Program, Department of Ecology and Genetics, Evolutionary Biology Centre (EBC), Uppsala University, Sweden.
Plant Ecology and Evolution, Department of Ecology and Genetics, Evolutionary Biology Centre (EBC), Uppsala University, Sweden.
Genome Biol Evol. 2019 Sep 1;11(9):2633-2652. doi: 10.1093/gbe/evz176.
In species with genetic sex determination, dosage compensation can evolve to equal expression levels of sex-linked and autosomal genes. Current knowledge about dosage compensation has mainly been derived from male-heterogametic (XX/XY) model organisms, whereas less is understood about the process in female-heterogametic systems (ZZ/ZW). In moths and butterflies, downregulation of Z-linked expression in males (ZZ) to match the expression level in females (ZW) is often observed. However, little is known about the underlying regulatory mechanisms, or if dosage compensation patterns vary across ontogenetic stages. In this study, we assessed dynamics of Z-linked and autosomal expression levels across developmental stages in the wood white (Leptidea sinapis). We found that although expression of Z-linked genes in general was reduced compared with autosomal genes, dosage compensation was actually complete for some categories of genes, in particular sex-biased genes, but equalization in females was constrained to a narrower gene set. We also observed a noticeable convergence in Z-linked expression between males and females after correcting for sex-biased genes. Sex-biased expression increased successively across developmental stages, and male-biased genes were enriched on the Z-chromosome. Finally, all five core genes associated with the ribonucleoprotein dosage compensation complex male-specific lethal were detected in adult females, in correspondence with a reduction in the expression difference between autosomes and the single Z-chromosome. We show that tuning of gene dosage is multilayered in Lepidoptera and argue that expression balance across chromosomal classes may predominantly be driven by enrichment of male-biased genes on the Z-chromosome and cooption of available dosage regulators.
在具有遗传性别决定的物种中，剂量补偿可以进化为使性连锁基因和常染色体基因的表达水平相等。目前关于剂量补偿的知识主要来自于雄性异型（XX/XY）模式生物，而对雌性异型系统（ZZ/ZW）中的这一过程了解较少。在蛾和蝴蝶中，常观察到雄性（ZZ）中 Z 连锁表达的下调，以匹配雌性（ZW）的表达水平。然而，对于潜在的调控机制，或者剂量补偿模式是否在个体发育阶段发生变化，人们知之甚少。在这项研究中，我们评估了在木白蝶（Leptidea sinapis）的发育阶段中 Z 连锁和常染色体表达水平的动态变化。我们发现，尽管 Z 连锁基因的表达总体上比常染色体基因低，但对于某些类别的基因，特别是性别偏向基因，实际上是完全补偿的，但雌性的均等化受到更窄的基因集的限制。我们还观察到，在纠正性别偏向基因后，雄性和雌性之间的 Z 连锁表达明显趋同。性别偏向表达随着发育阶段的推移逐渐增加，并且雄性偏向基因富集在 Z 染色体上。最后，在成年雌性中检测到与核糖核蛋白剂量补偿复合物雄性特异性致死相关的五个核心基因，与常染色体和单一 Z 染色体之间的表达差异减少相对应。我们表明，在鳞翅目昆虫中，基因剂量的调谐是多层次的，并认为跨染色体类别的表达平衡可能主要由 Z 染色体上雄性偏向基因的富集和可用剂量调节剂的共适应驱动。
