Pinheiro Vanessa Susan da Silva, Carvalho Natália Dayane Moura, Carmo Edson Júnior do, Schneider Carlos Henrique, Feldberg Eliana, Gross Maria Claudia
1 Graduate Program in Genetics, Conservation, and Evolutionary Biology, National Institute of Amazon Research , Manaus, Brazil .
2 Department of Genetics, Institute of Biological Sciences, Federal University of Amazonas, Manaus, Brazil .
Zebrafish. 2016 Apr;13(2):118-31. doi: 10.1089/zeb.2015.1187. Epub 2016 Feb 3.
Some families of Characiformes present the tendency toward stability of the karyotypic macrostructure as Curimatidae, which contains species with a 2n = 54 karyotype and metacentric and submetacentric chromosomes, however, some Potamorhina species contradict to this tendency. Some species of the central Amazon exhibit different diploid number and show intraspecific variation in the location of heterochromatin. By performing cytogenetic characterization by localization of heterochromatin and the nucleolus organizer region, as well as physical chromosome mapping using probes targeting 5S and 18S ribosomal DNA (rDNA), retroelement of Xiphophorus 1 (Rex1), Rex3, telomeres, and tropomyosin 1 (TPM1), we attempted to understand the evolutionary mechanisms involved in the differentiation of the Potamorhina species. The analyses showed that the heterochromatic regions of the examined species are distinct and transposable elements are involved in this evolutionary process, considering that the dynamic regions of the genome appear to include the terminal regions and particularly the heterochromatin-rich centromeric regions, which are involved in fission and fusion processes and promote the differentiation of chromosome pairs that bear ribosomal sites; these pairs were similar in the central Amazon species. Thus, we propose a phylogeny for this genus.
脂鲤目（Characiformes）的一些科呈现出核型宏观结构稳定的趋势，如库氏脂鲤科（Curimatidae），该科包含2n = 54核型以及中着丝粒和亚中着丝粒染色体的物种，然而，一些半线脂鲤属（Potamorhina）的物种却与这一趋势相悖。亚马孙河中部的一些物种表现出不同的二倍体数目，并在异染色质的位置上存在种内变异。通过对异染色质和核仁组织区进行定位来进行细胞遗传学特征分析，以及使用针对5S和18S核糖体DNA（rDNA）、剑尾鱼1号反转录元件（Rex1）、Rex3、端粒和原肌球蛋白1（TPM1）的探针进行物理染色体图谱分析，我们试图了解参与半线脂鲤属物种分化的进化机制。分析表明，所研究物种的异染色质区域是不同的，并且转座元件参与了这一进化过程，因为基因组的动态区域似乎包括末端区域，特别是富含异染色质的着丝粒区域，这些区域参与了裂变和融合过程，并促进了带有核糖体位点的染色体对的分化；这些染色体对在亚马孙河中部的物种中是相似的。因此，我们提出了该属的系统发育关系。
