Molecular Organization and Chromosomal Localization Analysis of rDNA Clusters in Autotetraploids Derived From Red Var. (♀) × (♂).

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