Supiwong Weerayuth, Liehr Thomas, Cioffi Marcelo B, Chaveerach Arunrat, Kosyakova Nadezda, Pinthong Krit, Tanee Tawatchai, Tanomtong Alongklod
Department of Biology Faculty of Science, Khon Kaen University, 123 Mitraphap Highway, Khon Kaen 40002, Muangkhonkaen District, Thailand.
Mol Cytogenet. 2013 Nov 22;6(1):51. doi: 10.1186/1755-8166-6-51.
In the present study, conventional and molecular cytogenetic studies were performed in the naked catfish Mystus bocourti (Siluriformes, Bagridae). Besides the conventional Giemsa staining, fluorescence in situ hybridization (FISH) using nine classes of repetitive DNAs namely 5S and 18S rDNAs, U2 snRNA, the microsatellites (CA)15 and (GA)15, telomeric repeats, and the retrotransposable elements Rex1, 3 and 6. was also performed.
M. bocourti had 2n = 56 chromosomes with a karyotype composed by 11 m + 11 sm + 6 st/a and a fundamental number (NF) equal to 100 in both sexes. Heteromorphic sex chromosome cannot be identified. The U2 snRNA, 5S and 18S rDNA were present in only one pair of chromosomes but none of them in a syntenic position. Microsatellites (CA)15 and (GA)15 showed hybridization signals at subtelomeric regions of all chromosomes with a stronger accumulation into one specific chromosomal pair. FISH with the telomeric probe revealed hybridization signals on each telomere of all chromosomes and interstitial telomeric sites (ITS) were not detected. The retrotransposable elements Rex1, 3 and 6 were generally spread throughout the genome.
In general, the repetitive sequences were not randomly distributed in the genome, suggesting a pattern of compartmentalization on the heterochromatic region of the chromosomes. Little is known about the structure and organization of bagrid genomes and the knowledge of the chromosomal distribution of repetitive DNA sequences in M. bocourti represents the first step for achieving an integrated view of their genomes.
在本研究中，对裸鲶鱼（Mystus bocourti，鲇形目，鲿科）进行了传统和分子细胞遗传学研究。除了传统的吉姆萨染色外，还使用了九类重复DNA进行荧光原位杂交（FISH），即5S和18S rDNA、U2 snRNA、微卫星（CA）15和（GA）15、端粒重复序列以及反转录转座元件Rex1、3和6。
裸鲶鱼有2n = 56条染色体，两性的核型均由11条中着丝粒染色体（m）+ 11条亚中着丝粒染色体（sm）+ 6条近端着丝粒/端着丝粒染色体（st/a）组成，臂数（NF）等于100。未发现异形性染色体。U2 snRNA、5S和18S rDNA仅存在于一对染色体中，但它们均不在同线位置。微卫星（CA）15和（GA）15在所有染色体的亚端粒区域显示杂交信号，且在一对特定染色体上积累更强。用端粒探针进行FISH显示所有染色体的每个端粒上都有杂交信号，未检测到间质端粒位点（ITS）。反转录转座元件Rex1、3和6普遍分布于整个基因组。
总体而言，重复序列在基因组中并非随机分布，这表明染色体异染色质区域存在分区模式。对于鲿科基因组的结构和组织知之甚少，而了解裸鲶鱼中重复DNA序列的染色体分布是全面了解其基因组的第一步。
