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Chromosomal Mapping of Repetitive DNAs in <b><i>Characidium</i></b> (Teleostei, Characiformes): Genomic Organization and Diversification of ZW Sex Chromosomes

2015; Karger Publishers; Volume: 146; Issue: 2 Linguagem: Inglês

10.1159/000437165

1424-8581

Priscilla Cardim Scacchetti, Ricardo Utsunomia, José Carlos Pansonato-Alves, Marcelo Ricardo Vicari, Roberto Ferreira Artoni, Cláudio Oliveira, Fausto Foresti,

Animal Genetics and Reproduction

The speciose neotropical genus <i>Characidium</i> has proven to be a good model for cytogenetic exploration. Representatives of this genus often have a conserved diploid chromosome number; some species exhibit a highly differentiated ZZ/ZW sex chromosome system, while others do not show any sex-related chromosome heteromorphism. In this study, chromosome painting using a W-specific probe and comparative chromosome mapping of repetitive sequences, including ribosomal clusters and 4 microsatellite motifs - (CA)₁₅, (GA)₁₅, (CG)₁₅, and (TTA)₁₀ -, were performed in 6 <i>Characidium</i> species, 5 of which possessed a heteromorphic ZW sex chromosome system. The W-specific probe showed hybridization signals on the W chromosome of all analyzed species, indicating homology among the W chromosomes. Remarkably, a single major rDNA-bearing chromosome pair was found in all species. The 18S rDNA localized to the sex chromosomes in <i>C</i>. <i>lanei</i>, <i>C</i>. <i>timbuiense</i> and <i>C</i>. <i>pterostictum</i>, while the major rDNA localized to one autosome pair in <i>C</i>. <i>vidali</i> and <i>C</i>. <i>gomesi</i>. In contrast, the number of 5S rDNA-bearing chromosomes varied. Notably, minor ribosomal clusters were identified in the W chromosome of <i>C</i>. <i>vidali</i>. Microsatellites were widely distributed across almost all chromosomes of the karyotypes, with a greater accumulation in the subtelomeric regions. However, clear differences in the abundance of each motif were detected in each species. In addition, the Z and W chromosomes showed the differential accumulation of distinct motifs. Our results revealed variability in the distribution of repetitive DNA sequences and their possible association with sex chromosome diversification in <i>Characidium</i> species.