暗褐肥尾蝎（蝎目，钳蝎科）的核型多样性及重复DNA的染色体组织
Karyotype diversity and chromosomal organization of repetitive DNA in Tityus obscurus (Scorpiones, Buthidae).
作者信息
Almeida Bruno Rafael Ribeiro de, Milhomem-Paixão Susana Suely Rodrigues, Noronha Renata Coelho Rodrigues, Nagamachi Cleusa Yoshiko, Costa Marlyson Jeremias Rodrigues da, Pardal Pedro Pereira de Oliveira, Coelho Johne Souza, Pieczarka Julio Cesar
机构信息
Laboratório de Citogenética, Centro de Estudos Avançados da Biodiversidade, Instituto de Ciências Biológicas, Universidade Federal do Pará, Avenida Augusto Corrêa, n°01, Av. Perimetral, s/n. Guamá, 66075-900, Belém, Pará, Brazil.
Instituto Federal de Educação, Ciência e Tecnologia de Goiás, Campus Valparaíso de Goiás, BR-040, km 6, Avenida Saia Velha, S/N, Área 8, Parque Esplanada V, 72876-601, Valparaíso de Goiás, Goiás, Brazil.
出版信息
BMC Genet. 2017 Apr 17;18(1):35. doi: 10.1186/s12863-017-0494-6.
BACKGROUND
Holocentric chromosomes occur in approximately 750 species of eukaryotes. Among them, the genus Tityus (Scorpiones, Buthidae) has a labile karyotype that shows complex multivalent associations during male meiosis. Thus, taking advantage of the excellent model provided by the Buthidae scorpions, here we analyzed the chromosomal distribution of several repetitive DNA classes on the holocentric chromosomes of different populations of the species Tityus obscurus Gervais, 1843, highlighting their involvement in the karyotypic differences found among them.
RESULTS
This species shows inter- and intrapopulational karyotype variation, with seven distinct cytotypes: A (2n = 16), B (2n = 14), C (2n = 13), D (2n = 13), E (2n = 12), F (2n = 12) and G (2n = 11). Furthermore, exhibits achiasmatic male meiosis and lacks heteromorphic sex chromosomes. Trivalent and quadrivalent meiotic associations were found in some cytotypes. In them, 45S rDNAs were found in the terminal portions of two pairs, while TTAGG repeats were found only at the end of the chromosomes. In the cytotype A (2n = 16), the U2 snRNA gene mapped to pair 1, while the H3 histone cluster and C t-1 DNA fraction was terminally distributed on all pairs. Mariner transposons were found throughout the chromosomes, with the exception of one individual of cytotype A (2n = 16), in which it was concentrated in heterochromatic regions.
CONCLUSIONS
Chromosomal variability found in T. obscurus are due to rearrangements of the type fusion/fission and reciprocal translocations in heterozygous. These karyotype differences follow a geographical pattern and may be contributing to reproductive isolation between populations analyzed. Our results also demonstrate high mobility of histone H3 genes. In contrast, other multigene families (45S rDNA and U2 snRNA) have conserved distribution among individuals. The accumulation of repetitive sequences in distal regions of T. obscurus chromosomes, suggests that end of chromosome are not covered by the kinetochore.
背景
全着丝粒染色体存在于大约750种真核生物中。其中，蒂氏蝎属（蝎子目，钳蝎科）具有不稳定的核型，在雄性减数分裂过程中表现出复杂的多价体联会。因此，利用钳蝎科蝎子提供的优秀模型，我们在此分析了1843年命名的暗蒂氏蝎不同种群的全着丝粒染色体上几种重复DNA类别的染色体分布，突出了它们与所发现的核型差异的关联。
结果
该物种表现出种群间和种群内的核型变异，有七种不同的细胞型：A（2n = 16）、B（2n = 14）、C（2n = 13）、D（2n = 13）、E（2n = 12）、F（2n = 12）和G（2n = 11）。此外，表现出无交叉的雄性减数分裂，并且缺乏异型性染色体。在一些细胞型中发现了三价体和四价体减数分裂联会。在这些细胞型中，45S rDNA位于两对染色体的末端部分，而TTAGG重复序列仅在染色体末端发现。在细胞型A（2n = 16）中，U2 snRNA基因定位于第1对染色体，而H3组蛋白簇和C t-1 DNA片段末端分布于所有染色体对。水手转座子在整个染色体上均有发现，但细胞型A（2n = 16）的一个个体除外，在该个体中它集中在异染色质区域。
结论
暗蒂氏蝎中发现的染色体变异是由于杂合状态下的融合/裂变和相互易位类型的重排所致。这些核型差异遵循地理模式，可能导致所分析种群之间的生殖隔离。我们的结果还证明了组蛋白H3基因的高迁移率。相比之下，其他多基因家族（45S rDNA和U2 snRNA）在个体间具有保守的分布。暗蒂氏蝎染色体远端区域重复序列的积累表明，染色体末端未被动粒覆盖。
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