牙鲆和半滑舌鳎5S rDNA基因的染色体定位及鲽形目5种鱼类的分子系统学分析

利用荧光原位杂交(FISH)技术将5S rDNA基因定位在牙鲆和半滑舌鳎染色体上,结果表明,5S rDNA基因在雌、雄性半滑舌鳎的一对同源染色体上分别存在2个杂交信号位点;在二、三倍体牙鲆的同源染色体上分别存在2个和3个杂交信号位点,杂交信号明显且特异。本研究首次将5S rDNA基因定位在半滑舌鳎和三倍体牙鲆的染色体上,为牙鲆及半滑舌鳎倍性鉴定、染色体鉴别提供了有效方法。此外,根据牙鲆5S rDNA基因编码区序列设计引物,扩增出大菱鲆和半滑舌鳎5S rDNA基因编码区序列,与鲽、塞内加尔鳎、大口黑鲈、七鳃鳗的5SrDNA基因序列进行同源性比较后发现,5种鲽形目鱼类5S rDNA基因序列同源性高达98.3%,系统发生分析结果显示5种鲽形目鱼类聚为一支;各序列中GC含量均显著高于AT含量。

Chromosome mapping of 5S rDNA in olive flounder (Paralichthys olivaceus) and half-smooth tongue-sole (Cynoglossus semilaevis) and molecular systematics analysis of five flatfishes

Using fluorescence in situ hybridization (FISH), 5S rDNA gene was mapped on chromosomes of half-smooth tongue-sole(Cynoglossus semilaevis)and olive flounder(Paralichthys olivaceus)for the first time. The results showed that 5S rDNA has two hybridization signal loci in a pair of homologous chromosomes of male and female half-smooth tongue-sole, respectively; 5S rDNA has two and three hybridization signal loci in a pair of homologous chromosomes of diploid and triploid olive flounder, respectively, referring to the clear and specific hybridization signals. FISH mapping of 5S rDNA genes on the chromosomes of diploid half-smooth tongue-sole and triploid olive flounder provides a feasible method for ploidy and chromosome identification of half-smooth tongue-sole and olive flounder. In addition, the coding region sequences of 5S rDNA gene of turbot (Scophthalmus maximus) and half-smooth tongue-sole were amplified using same primers designed for olive flounder 5 S rDNA gene, and the phylogenetic analysis of the 5S rDNA genes in four species of flatfishes, including plaice(Pleuronectes platessa), senegalese sole (Solea senegalensis), largemouth bass(Micropterus salmoides) and arctic lamprey(Lampetra japonica) showed that the 5S rDNA gene of five species of flatfishes shared high homology (98.3%) and gathered into a branch. The GC content was significantly higher than the AT content in conservative sequence of 5S rDNA coding region of these five species of flatfishes.