More on the cytogenetics of Rineloricaria pentamaculata

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More on the cytogenetics of Rineloricaria pentamaculata

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Glugoski, L., Deon, G. A., Nogaroto, V., Moreira-Filho, O., & Vicari, M. R. (2023). Robertsonian fusion site in Rineloricaria pentamaculata (Siluriformes: Loricariidae): involvement of 5S rDNA and satellite sequences. Cytogenetic and Genome Research.
https://doi.org/10.1159/000530636
https://www.karger.com/Article/Abstract/530636
Abstract
Cytogenetic studies demonstrated that unstable chromosomal sites in armored catfishes (Loricariidae) triggered
intense karyotypic diversification, mainly derived from Robertsonian (Rb) rearrangements. In Loricariinae, the
presence of ribosomal DNA (rDNA) clusters and their flanking repeated regions (such as microsatellites or partial
transposable element sequences) were proposed to facilitate chromosomal rearrangements. Hence, this study aimed
to characterize the numerical chromosomal polymorphism observed in and to evaluate
the chromosomal rearrangements which originated diploid chromosome number (2n) variation, from 56 to 54. Our
data indicate a centric fusion event between acrocentric chromosomes of pairs 15 and 18, bearing 5S rDNA sites on
their short (p) arms. This chromosome fusion established the numeric polymorphism, decreasing the 2n from original
56 (karyomorph A) to 55 in karyomorph B, and 54 in karyomorph C. Although vestiges of telomeric sequences were
evidenced at the fusion point, no 5S rDNA was detected in this region. The acrocentric chromosomes involved in the
origin of the fusion were enriched with (CA)n and (GA)n microsatellites. Repetitive sequences in the acrocentric
chromosomes subtelomeres have facilitated the rearrangement. Our study thus reinforces the view on important
role of particular repetitive DNA classes in promoting chromosome fusions which frequently drive Rineloricaria
karyotype evolution.
Keywords: armored catfishes, centric fusion, chromosomal instability sites, end-to-end fusion, karyotype evolution.
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