Diverse stages of sex-chromosome differentiation in tinamid birds: evidence from crossover analysis in Eudromia elegans and Crypturellus tataupa
Diverse stages of sex-chromosome differentiation in tinamid birds: evidence from crossover analysis in Eudromia elegans and Crypturellus tataupa
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DOI：
10.1007/s10709-011-9581-1
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发表时间：
2011-06-01
期刊：
影响因子：
1.5
通讯作者：
Ines Pigozzi, Maria
中科院分区：
文献类型：
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作者：
Ines Pigozzi, Maria
所有现存的鸟类都有相同的性染色体系统：ZZ雄性和ZW雌性，但原始的古鸟类和新生殖器内的绝大多数鸟类在性染色体分化阶段上存在显着差异。进化上与Ratites相近的是新热带目Tinamiformes，关于ZW对的形态和组成几乎没有人研究过。因此，探索这一类群中Z染色体和W染色体的同源性程度可能会揭示鸟类性染色体进化的关键特征。我们定位了粗线期二价体上的交叉标记MLH1焦点，以确定Z和W染色体所共享的同源区的大小和在两种五倍体中的定位：Eudroia elegans和Crypturellus talaupa。我们发现这两个物种的同源(伪常染色体)区域在大小上存在显著差异。它们都在Z染色体和W染色体的长臂上有一个单一的重组事件。然而，在线虫中，伪常染色体区域占据W染色体的四分之一，而在线虫中，伪常染色体区域仅限于W长臂的顶端。这两种线虫的W染色体的异染色质含量不同：在线虫中，它显示出末端的常染色质片段，而在线虫中，它是完全异染色质的。这些结果表明，与Rate相比，Tinamamy具有更多样化的分化阶段的ZW对。最后，讨论了鸟类原性染色体开始从长臂末端向着丝粒方向分化的观点。
All extant birds share the same sex-chromosome system: ZZ males and ZW females with striking differences in the stages of sex-chromosome differentiation between the primitive palaeognathus ratites and the large majority of avian species grouped within neognaths. Evolutionarily close to ratites is the neotropical order Tinamiformes that has been scarcely explored regarding their ZW pair morphology and constitution. Tinamous, when compared to ratites, constitute a large group among Palaeognathae, therefore, exploring the extent of homology between the Z and W chromosomes in this group might reveal key features on the evolution of the avian sex chromosomes. We mapped MLH1 foci that are crossover markers on pachytene bivalents to determine the size and localization of the homologous region shared by the Z and W chromosomes in two tinamous: Eudromia elegans and Crypturellus tataupa. We found that the homologous (pseudoautosomal) region differ significantly in size between these two species. They both have a single recombination event on the long arm of the acrocentric Z and W chromosomes. However, in E. elegans the pseudoautosomal region occupies one-fourth of the W chromosome, while in C. tataupa it is restricted to the tip of the long arm of the W. The W chromosomes in these two species differ in their heterochromatin content: in E. elegans it shows a terminal euchromatic segment and in C. tataupa is completely heterochromatic. These results show that tinamous have ZW pairs with more diversified stages of differentiation compared to ratites. Finally, the idea that the avian proto-sex chromosomes started to diverge from the end of the long arm towards the centromere of an acrocentric pair is discussed.