Laboratory of Ecological and Evolutionary Genetics, Institute of Biological and Health Sciences, Federal University of Viçosa Campus Rio Paranaíba, Rio Paranaíba, Brazil.
Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, Brazil.
Cytogenet Genome Res. 2024;164(2):121-132. doi: 10.1159/000539429. Epub 2024 Jul 30.
The mapping of the satellite DNA on chromosomes is vital to understanding the distribution and evolution of repetitions in the genome since these chromosomal studies have shown the origin, evolutionary mode, and function of repetitive sequences. This study aimed to prospect the satellitome and determine its location in the genome of two cryptic species of Hypostomus, H. aff. ancistroides and H. ancistroides, with and without XX/XY sexual chromosome system.
Mitotic chromosomes and DNA extraction were obtained according to protocols. After the whole genome sequencing, the satDNAs were retrieved, amplified, and hybridized in chromosome preparations for male and female individuals.
We found 30 satellite families (47 variants, two superfamilies) in H. ancistroides and 38 satellite families (45 variants, four superfamilies) in H. aff. ancistroides. The sequences varied from 14 bp to 2,662 bp in H. ancistroides and from 14 bp to 2,918 bp in H. aff. ancistroides. We did not observe any tandem repeats that were exclusive to each of the libraries; however, many sequences showed very different abundances and copy numbers between the libraries. Four satDNAs did not hybridize on the chromosomes of either species. Conversely, one satDNA hybridized in both species, HxySat1-80. However, the phenotypes found varied among species, populations, and in the same individual. There was no sign of HanSat3-464 and HanSat11-335 in any individuals of H. aff. ancistroides, but markings were in the chromosomes of H. ancistroides. HxySat12-1127 and HxySat8-52, on the other hand, were only hybridized in H. aff. ancistroides, while H. ancistroides had a negative sign. No hybridization of satDNAs was found in the X and Y sex chromosomes as they were mostly composed of euchromatin.
We distinguish H. aff. ancistroides as genetically different from H. ancistroides, recognizing that such characteristics go far beyond morphological, karyotypic, and molecular data. Our data support the differential abundance and location of satellite DNAs and confirm that many organisms, including fish, have repetitive sequences that validate the library hypothesis. All found and validated satDNAs and the characterization of the satellitomes of the two species represent important contributions to cytogenomic studies of the genus Hypostomus.
卫星 DNA 在染色体上的定位对于理解基因组中重复序列的分布和进化至关重要，因为这些染色体研究表明了重复序列的起源、进化模式和功能。本研究旨在探测 Hypostomus 两个隐种的卫星体，并确定其在具有和不具有 XX/XY 性染色体系统的 H. ancistroides 和 H. aff. ancistroides 基因组中的位置。
根据方案获得有丝分裂染色体和 DNA 提取。全基因组测序后，回收 satDNA，在雄性和雌性个体的染色体制备物中扩增和杂交。
我们在 H. ancistroides 中发现了 30 个卫星家族（47 个变体，两个超家族），在 H. aff. ancistroides 中发现了 38 个卫星家族（45 个变体，四个超家族）。H. ancistroides 中的序列长度从 14bp 到 2662bp 不等，H. aff. ancistroides 中的序列长度从 14bp 到 2918bp 不等。我们没有观察到任何仅存在于每个文库中的串联重复序列，但许多序列在文库之间表现出非常不同的丰度和拷贝数。有 4 个 satDNA 在两个物种的染色体上都没有杂交。相反，一个 satDNA 在两个物种中都杂交，即 HxySat1-80。然而，在不同物种、种群和同一个体中观察到的表型存在差异。在任何 H. aff. ancistroides 的个体中都没有 HanSat3-464 和 HanSat11-335 的标记，但在 H. ancistroides 的染色体上却有标记。另一方面，HxySat12-1127 和 HxySat8-52 仅在 H. aff. ancistroides 中杂交，而 H. ancistroides 则为阴性。由于 X 和 Y 性染色体主要由常染色质组成，因此没有发现 satDNA 的杂交。
我们认为 H. aff. ancistroides 在遗传上与 H. ancistroides 不同，这表明其特征远远超出了形态学、核型和分子数据。我们的数据支持卫星 DNA 的丰度和位置的差异，并证实包括鱼类在内的许多生物都有重复序列，这验证了文库假说。所有发现和验证的 satDNA 以及对两个物种的卫星体的特征描述，都为 Hypostomus 属的细胞遗传学研究做出了重要贡献。
