Localization and Characterization of the 5S rDNA Bearing Chromosome in Two Steindachneridion Species by Means of Different Cytogenetic Techniques

Abstract

Summary Karyotype macrostructure and nucleolar organizer regions have often been studied in Neotropical siluriform fishes, but data about structural rearrangements and gene mapping are scarce. 5S rDNA is localized and characterized in Sorubiminae species (Steindachneridion melanodermatum and S. scriptum) using fluorescence in situ hybridization, C-and G-banding and restriction enzyme banding (AluI, BamHI and EcoRI). Chromosome mapping of 5S rDNA genes showed only one site located on the short arms of subtelocentric chromosome pair (chromosome 23) in both species, with no apparent polymorphisms. This region is C-positive and shows a clear Gband, having no cleavage sites for the restriction enzymes tested. These genes are not syntenical with the 18S ones and their karyotype location remains conserved in the species studied, appearing as a cytogenetic marker.

Chromosomal polymorphism in Steindachneridion melanodermatum Garavello, 2005 (Siluriformes, Pimelodidae): a reappraisal the existence of sex chromosome system in the species

“…The 5S rDNA has been considered a useful tool for phylogenetic inference in several groups Kavalco et al 2004,) In S. melanodermatum, however, this cytogenetic marker has been found conserved. Swarça et al (2009) described the 5S rDNA of S. melanodermatum in the subterminal region of short arm of first subtelocentric pair, a result also observed in this study. Among the Siluriformes order some species had the location of 5S rDNA studied.…”

An uncommon co-localization of rDNA 5S with major rDNA clusters in Callichthyidae (Siluriformes): a report case in Corydoras carlae Nijssen & Isbrücker, 1983

“…In Corydoras carlae , the 5S rDNA was displayed at terminal position on the long arm of the metacentric pair 6. The presence of one chromosome pair bearing 5S rDNA is a common feature in different families of Siluriformes (Swarça et al 2009), although multiple loci of 5S rDNA have been observed in Callichthyinae (Table 1). Inter– and intra–individual numerical and position variations of 5S rDNA cistrons have been observed in Callichthyidae and seem to represent a species-specific marker.…”

Cytogenetic characterization of F1, F2 and backcross hybrids of the Neotropical catfish species Pseudoplatystoma corruscans and Pseudoplatystoma reticulatum (Pimelodidae, Siluriformes)

“…Although few chromosomal mapping studies have examined the 5S gene in the Pimelodidae, the evidence indicates the prevalence of only two chromosomes related to these ribosomal sites ( Swarça et al , 2009 ; Carvalho et al , 2010 ). As shown here, the 5S ribosomal gene was located pericentromerically on one chromosomal pair in P. reticulatum and P. corruscans , as also observed by Swarça et al (2005) and Neto et al (2011) ; the hybrid lineages showed 5S demarcations at the same chromosomal positions as their parental lineages, thus conforming previous observations for this fish group.…”