Departamento de Biologia Estrutural, Molecular e Genética, Universidade Estadual de Ponta Grossa, Ponta Grossa, PR, Brazil.
J Fish Biol. 2010 Apr;76(5):1094-116. doi: 10.1111/j.1095-8649.2010.02564.x.
Constitutive heterochromatin represents a substantial portion of the eukaryote genome, and it is mainly composed of tandemly repeated DNA sequences, such as satellite DNAs, which are also enriched by other dispersed repeated elements, including transposons. Studies on the organization, structure, composition and in situ localization of satellite DNAs have led to consistent advances in the understanding of the genome evolution of species, with a particular focus on heterochromatic domains, the diversification of heteromorphic sex chromosomes and the origin and maintenance of B chromosomes. Satellite DNAs can be chromosome specific or species specific, or they can characterize different species from a genus, family or even representatives of a given order. In some cases, the presence of these repeated elements in members of a single clade has enabled inferences of a phylogenetic nature. Genomic DNA restriction, using specific enzymes, is the most frequently used method for isolating satellite DNAs. Recent methods such as C(0)t-1 DNA and chromosome microdissection, however, have proven to be efficient alternatives for the study of this class of DNA. Neotropical ichthyofauna is extremely rich and diverse enabling multiple approaches with regard to the differentiation and evolution of the genome. Genome components of some species and genera have been isolated, mapped and correlated with possible functions and structures of the chromosomes. The 5SHindIII-DNA satellite DNA, which is specific to Hoplias malabaricus of the Erythrinidae family, has an exclusively centromeric location. The As51 satellite DNA, which is closely correlated with the genome diversification of some species from the genus Astyanax, has also been used to infer relationships between species. In the Prochilodontidae family, two repetitive DNA sequences were mapped on the chromosomes, and the SATH 1 satellite DNA is associated with the origin of heterochromatic B chromosomes in Prochilodus lineatus. Among species of the genus Characidium and the Parodontidae family, amplifications of satellite DNAs have demonstrated that these sequences are related to the differentiation of heteromorphic sex chromosomes. The possible elimination of satellite DNA units could explain the genome compaction that occurs among some species of Neotropical Tetraodontiformes. These topics are discussed in the present review, showing the importance of satellite DNA analysis in the differentiation and karyotype evolution of Actinopterygii.
常染色质代表真核生物基因组的大部分，主要由串联重复的 DNA 序列组成，如卫星 DNA，它还富含其他分散的重复元件，包括转座子。对卫星 DNA 的组织、结构、组成和原位定位的研究促进了对物种基因组进化的理解，特别是对异染色质区域、异型性性染色体的多样化以及 B 染色体的起源和维持的理解。卫星 DNA 可以是染色体特异性或物种特异性的，也可以是属、科甚至特定目代表的不同物种的特征。在某些情况下，同一分支中的这些重复元件的存在使得可以进行系统发育推断。使用特定酶对基因组 DNA 进行限制是分离卫星 DNA 最常用的方法。然而，最近的方法，如 C(0)t-1 DNA 和染色体微切割，已被证明是研究此类 DNA 的有效替代方法。新热带鱼类区系极其丰富多样，使我们可以对基因组的分化和进化进行多种研究。一些物种和属的基因组成分已被分离、作图并与染色体的可能功能和结构相关联。Erythrinidae 科的 Hoplias malabaricus 所特有的 5SHindIII-DNA 卫星 DNA 具有独特的着丝粒位置。与某些 Astyanax 属物种基因组多样化密切相关的 As51 卫星 DNA 也被用于推断物种之间的关系。在 Prochilodontidae 科中，有两个重复 DNA 序列被映射到染色体上，并且 SATH 1 卫星 DNA 与 Prochilodus lineatus 中异染色质 B 染色体的起源有关。在 Characidium 属和 Parodontidae 科的物种中，卫星 DNA 的扩增表明这些序列与异型性性染色体的分化有关。卫星 DNA 单元的可能消除可以解释新热带四齿鲀目中一些物种的基因组紧缩。本文综述了这些主题，展示了卫星 DNA 分析在硬骨鱼纲的分化和染色体进化中的重要性。
