Molecular Organization and Chromosomal Localization Analysis of 5S rDNA Clusters in Autotetraploids Derived From Carassius auratus Red Var. (♀) × Megalobrama amblycephala (♂)

Abstract

The autotetraploid fish (4<i>n</i> = 200, RRRR) (abbreviated as 4<i>n</i>RR) resulted from the whole genome duplication of red crucian carp (<i>Carassius auratus</i> red var., 2<i>n</i> = 100, RR) (abbreviated as RCC). During investigation of the influence of polyploidization on organization and evolution of the multigene family of <i>5S</i> rDNA, molecular organization and chromosomal localization of the <i>5S</i> rDNA were characterized in autotetraploid fish. By sequence analysis of the coding region (<i>5S</i>) and adjacent non-transcribed spacer (NTS), three distinct <i>5S</i> rDNA units (type I: 203 bp; type II: 340 bp; and type III: 477bp) were identified and characterized in 4<i>n</i>RR. These <i>5S</i> rDNA units were inherited from their female parent (RCC), in which obvious base variations in NTS and array recombination of repeat units were found. Using fluorescence <i>in situ</i> hybridization employing different <i>5S</i> rDNA units as probes, these <i>5S</i> rDNA clusters were localized in chromosomes of 4<i>n</i>RR, respectively, and showed obvious loss of chromosomal loci (type I and type II). Our data revealed genetic variation of the <i>5S</i> rDNA multigene family in the genome of autopolyploid fish. Furthermore, results provided new insights into the evolutionary patterns of this vertebrate multigene family.