Bertocchi Natasha Avila, de Oliveira Thays Duarte, Del Valle Garnero Analía, Coan Rafael Luiz Buogo, Gunski Ricardo José, Martins Cesar, Torres Fabiano Pimentel
Programa de Pós-graduação em Genética e Biologia Molecular, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Rio Grande do Sul, 91501-970, Brazil.
Programa de Pós-graduação em Biologia Animal, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Rio Grande do Sul, 91540-000, Brazil.
Chromosome Res. 2018 Dec;26(4):333-343. doi: 10.1007/s10577-018-9592-1. Epub 2018 Nov 29.
Birds have relatively few repetitive sequences compared to other groups of vertebrates; however, the members of order Piciformes (woodpeckers) have more of these sequences, composed mainly of transposable elements (TE). The TE most often found in birds is a retrotransposon chicken repeat 1 (CR1). Piciformes lineages were subjected to an expansion of the CR1 elements, carrying a larger fraction of transposable elements. This study compared patterns of chromosome distribution among five bird species, through chromosome mapping of the CR1 sequence and reconstructed their phylogenetic tree. We analyzed several members of Piciformes (Colaptes campestris, Colaptes melanochloros, Melanerpes candidus, and Veniliornis spilogaster), as well as Galliformes (Gallus gallus). Gallus gallus is the species with which most genomic and hence cytogenetic studies have been performed. The results showed that CR1 sequences are a monophyletic group and do not depend on their hosts. All species analyzed showed a hybridization signal by fluorescence in situ hybridization (FISH). In all species, the chromosomal distribution of CR1 was not restricted to heterochromatin regions in the macrochromosomes, principally pair 1 and the Z sex chromosome. Accumulation in the Z sex chromosomes can serve as a refuge for transposable elements. These results highlight the importance of transposable elements in host genomes and karyotype evolution.
与其他脊椎动物类群相比，鸟类的重复序列相对较少；然而，啄木鸟目（啄木鸟）的成员拥有更多这类序列，主要由转座元件（TE）组成。鸟类中最常见的TE是逆转座子鸡重复序列1（CR1）。啄木鸟目谱系经历了CR1元件的扩张，携带了更大比例的转座元件。本研究通过CR1序列的染色体定位比较了五种鸟类的染色体分布模式，并重建了它们的系统发育树。我们分析了啄木鸟目的几个成员（平原扑翅鴷、绿扑翅鴷、白腹食果啄木鸟和斑腰扑翅鴷），以及鸡形目（原鸡）。原鸡是进行了最多基因组以及细胞遗传学研究的物种。结果表明，CR1序列是一个单系群，不依赖于它们的宿主。所有分析的物种通过荧光原位杂交（FISH）都显示出杂交信号。在所有物种中，CR1的染色体分布并不局限于大染色体中的异染色质区域，主要是第1对染色体和Z性染色体。在Z性染色体上的积累可以作为转座元件的一个避难所。这些结果突出了转座元件在宿主基因组和核型进化中的重要性。
