Molecular cytogenetic characterization of 5S ribosomal DNA families in giant salamanders (Amphibia, Urodela)

Abstract

Entire 5S ribosomal DNA (rDNA), including coding and non-transcribed spacer (NTS) regions from three giant salamander species, Andrias japonicus, A. davidianus, and Cryptobranchus alleganiensis, were sequenced to know the organization of the 5S rDNA multigene family in the giant salamander genome. Owing to the similarity of the sequences in the gene region, the 5S rDNA in these species were clearly divided into four types. Types A and D were detected as speciesspecific for A. japonicus and A. davidianus, respectively, while types B and C were isolated from all three species. Comparative analysis suggests the presence of two or three types of the 5S rDNA in the genome of giant salamanders such as the somatic and oocyte types observed in other amphibian species. Further analysis using fluorescence in-situ hybridization (FISH) to the embryonic chromosomes from A. japonicus localized 5S rDNA to the subterminal region of a single medium-sized acrocentric chromosome pair.