Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, Brazil.
Chromosome Res. 2012 May;20(4):427-33. doi: 10.1007/s10577-012-9286-z. Epub 2012 Jun 19.
The Akodontini is the second most speciose tribe of sigmodontine rodents, one of the most diverse groups of neotropical mammals. Molecular phylogenetic analyses are discordant regarding the interrelationships of genera, with low support for some clades. However, two clades are concordant, one (clade A) with Akodon sensu strictu (excluding Akodon serrensis), "Akodon" serrensis, Bibimys, Deltamys, Juscelinomys, Necromys, Oxymycterus, Podoxymys, Thalpomys and Thaptomys, and another (clade B) with Blarinomys, Brucepattersonius, Kunsia, Lenoxus and Scapteromys. Here, we present chromosome painting using Akodon paranaensis (APA) Y paint, after suppression of simple repetitive sequences, on ten Akodontini genera. Partial Y chromosome homology, in addition to the homology already reported on the Akodon genus, was detected on the Y chromosomes of "A." serrensis, Thaptomys, Deltamys, Necromys and Thalpomys and on Y and X chromosomes in Oxymycterus. In Blarinomys, Brucepattersonius, Scapteromys and Kunsia, no APA Y signal was observed using different hybridization conditions; APA X paint gave positive signals only on the X chromosome in all genera. The Y chromosome homology was variable in size and positioning among the species studied as follow: (1) whole acrocentric Y chromosome in Akodon and "A." serrensis, (2) Yp and pericentromeric region in submetacentric Y of Necromys and Thaptomys, (3) pericentromeric region in acrocentric Y of Deltamys, (4) distal Yq in the acrocentric Y chromosome of Thalpomys and (5) proximal Yq in the acrocentric Y and Xp in the basal clade A genus Oxymycterus. The results suggest that the homology involves pairing (pseudoautosomal) and additional regions that have undergone rearrangement during divergence. The widespread Y homology represents a phylogenetic signal in Akodontini that provides additional evidence supporting the monophyly of clade A. The findings also raise questions about the evolution of the pseudoautosomal region observed in Oxymycterus. The Y chromosomes of these closely related species seem to have undergone dynamic rearrangements, including restructuring and reduction of homologous segments. Furthermore, the changes observed may indicate progressive attrition of the Y chromosome in more distantly related species.
阿孔豚鼠是细尾滨鼠科第二大物种丰富的部落，也是新热带地区哺乳动物中最多样化的群体之一。分子系统发育分析对于属之间的相互关系存在分歧，一些分支的支持率较低。然而，有两个分支是一致的，一个（分支 A）包括狭义的阿孔豚鼠（不包括阿孔豚鼠属 serrensis）、“阿孔豚鼠”属 serrensis、比比米鼠、德尔塔鼠、朱塞利诺鼠、内克罗马鼠、Oxymycterus、波多西鼠、塔耳坡鼠和塔普托鼠，另一个（分支 B）包括布拉里诺鼠、布鲁克帕森鼠、昆西亚鼠、列努克斯鼠和斯卡特罗鼠。在这里，我们使用经过简单重复序列抑制的阿孔豚鼠属 paranaensis（APA）Y 染色体涂染，对阿孔豚鼠族的十个属进行了染色体涂染。除了在阿孔豚鼠属中已经报道的同源性外，在“阿孔豚鼠”属 serrensis、塔耳坡鼠、德尔塔鼠、内克罗马鼠和塔普托鼠的 Y 染色体以及 Oxymycterus 的 Y 和 X 染色体上也检测到了部分 Y 染色体同源性。在布拉里诺鼠、布鲁克帕森鼠、斯卡特罗鼠和昆西亚鼠中，使用不同的杂交条件没有观察到 APA Y 信号；APA X 染色体涂染仅在所有属的 X 染色体上产生阳性信号。在所研究的物种中，Y 染色体同源性的大小和定位各不相同，具体情况如下：（1）在阿孔豚鼠和“阿孔豚鼠”属 serrensis 中，整个近端着丝粒 Y 染色体；（2）在 Necromys 和塔耳坡鼠的亚中着丝粒 Y 染色体中，Yp 和着丝粒区；（3）在德尔塔鼠的近端着丝粒 Y 染色体中，着丝粒区；（4）在塔普托鼠的近端着丝粒 Y 染色体中，Yq 远端；（5）在 Oxymycterus 属的近端着丝粒 Y 和 Xp 中，在基部分支 A 属的近端着丝粒 Y 和 Xp 中。结果表明，同源性涉及配对（假常染色体）和在分化过程中发生重排的额外区域。广泛的 Y 染色体同源性代表了阿孔豚鼠族中的一个系统发育信号，为分支 A 的单系性提供了额外的证据支持。这些发现还引发了关于在 Oxymycterus 中观察到的假常染色体区进化的问题。这些密切相关物种的 Y 染色体似乎经历了动态重排，包括同源片段的结构重组和减少。此外，观察到的变化可能表明在更远缘的物种中，Y 染色体逐渐消失。
