Institute of Science and Technology Austria, Klosterneuburg, Austria.
Genome Biol Evol. 2019 Apr 1;11(4):1033-1044. doi: 10.1093/gbe/evz053.
Males and females of Artemia franciscana, a crustacean commonly used in the aquarium trade, are highly dimorphic. Sex is determined by a pair of ZW chromosomes, but the nature and extent of differentiation of these chromosomes is unknown. Here, we characterize the Z chromosome by detecting genomic regions that show lower genomic coverage in female than in male samples, and regions that harbor an excess of female-specific SNPs. We detect many Z-specific genes, which no longer have homologs on the W, but also Z-linked genes that appear to have diverged very recently from their existing W-linked homolog. We assess patterns of male and female expression in two tissues with extensive morphological dimorphism, gonads, and heads. In agreement with their morphology, sex-biased expression is common in both tissues. Interestingly, the Z chromosome is not enriched for sex-biased genes, and seems to in fact have a mechanism of dosage compensation that leads to equal expression in males and in females. Both of these patterns are contrary to most ZW systems studied so far, making A. franciscana an excellent model for investigating the interplay between the evolution of sexual dimorphism and dosage compensation, as well as Z chromosome evolution in general.
卤虫（Artemia franciscana）是一种常用于水族馆贸易的甲壳类动物，其雄性和雌性具有高度的二态性。性别由一对 ZW 染色体决定，但这些染色体的分化性质和程度尚不清楚。在这里，我们通过检测雌性样本中基因组覆盖度低于雄性样本的基因组区域以及包含雌性特异性 SNP 过剩的区域来表征 Z 染色体。我们检测到许多 Z 特异性基因，这些基因在 W 染色体上不再有同源物，但也有 Z 连锁基因似乎是最近才从其现有的 W 连锁同源物中分化出来的。我们评估了在两个具有广泛形态二态性的组织（性腺和头部）中雄性和雌性的表达模式。与它们的形态一致，两种组织中都存在性别偏向表达。有趣的是，Z 染色体并不富集性别偏向基因，实际上似乎有一种剂量补偿机制，导致雄性和雌性的表达相等。这些模式都与迄今为止研究的大多数 ZW 系统相反，使 A. franciscana 成为研究性二态性和剂量补偿进化以及 Z 染色体进化之间相互作用的绝佳模型。
