Gornung Ekaterina, Colangelo Paolo, Annesi Flavia
Department of Animal and Human Biology, University of Rome Sapienza, via A. Borelli 50, 00161 Rome, Italy.
Genome. 2007 Sep;50(9):787-95. doi: 10.1139/g07-058.
This paper describes a study of the 5S ribosomal RNA genes (5S rDNA) in a group of 6 species belonging to 4 genera of Mugilidae. In these 6 species, the relatively short 5S rDNA repeat units, generated by PCR and ranging in size from 219 to 257 bp, show a high level of intragenomic homogeneity of both coding and spacer regions (NTS-I). Phylogenetic reconstructions based on this data set highlight the greater phylogenetic and genetic diversity of Mugil cephalus and Oedalechilus labeo compared with the genera Liza and Chelon. Comparative sequence analysis revealed significant conservation of the short 5S rDNA repeat units across Chelon and Liza. Moreover, a second size class of 5S rDNA repeat units, ranging from roughly 800 to 1100 bp, was produced in the Liza and Chelon samples. Only short 5S rDNA repeat units were found in M. cephalus and O. labeo. The sequences of the long 5S rDNA repeat units, obtained in Chelon labrosus and Liza ramada, differ owing to the presence of 2 large insertion/deletions (indels) in the spacers (NTS-II) and show considerable sequence identity with NTS-I spacers. Interspecific sequence variation of NTS-II spacers, excluding the indels, is low. Southern-blot hybridization patterns suggest an intermixed arrangement of short and long repeat units within a single chromosome locus.
本文描述了对鲻科4个属的6个物种的5S核糖体RNA基因（5S rDNA）的研究。在这6个物种中，通过PCR产生的相对较短的5S rDNA重复单元，大小在219至257 bp之间，其编码区和间隔区（NTS-I）在基因组内具有高度同质性。基于该数据集的系统发育重建突出了与丽鲻属和龟鲻属相比，鲻鱼和印度丽鲻的系统发育和遗传多样性更高。比较序列分析显示，龟鲻属和丽鲻属的短5S rDNA重复单元具有显著的保守性。此外，在丽鲻属和龟鲻属的样本中产生了第二类大小的5S rDNA重复单元，大小约为800至1100 bp。在鲻鱼和印度丽鲻中仅发现了短5S rDNA重复单元。在缘边龟鲻和拉氏丽鲻中获得的长5S rDNA重复单元序列因间隔区（NTS-II）中存在2个大的插入/缺失（indel）而不同，并且与NTS-I间隔区具有相当的序列同一性。排除indel后，NTS-II间隔区的种间序列变异较低。Southern杂交模式表明，在单个染色体位点内短重复单元和长重复单元呈混合排列。
