Chromosomal features of nucleolar dominance in hybrids between the Neotropical fish Leporinus macrocephalus and Leporinus elongatus (Characiformes, Anostomidae)

Abstract

In the present study, the chromosomal mechanisms of nucleolar dominance were analyzed in the hybrid lineage "Piaupara," which resulted from crossing the Leporinus macrocephalus female (Piauçu) and L. elongatus male (Piapara) fish. The analyses demonstrated that, in the hybrid, the nucleolar region inherited from L. elongatus presented higher activity, with expression in 100% of the cells, whereas the nucleolar region from L. macrocephalus appeared active at a frequency of 11.6%. The FISH technique with an 18S probe showed that the ribosomal DNA of the nucleolar region was not lost in the hybrid, and the results therefore demonstrated invariable marks in two chromosomes, each originating from one parent. An interesting difference between the nucleolar regions of the parental species was the association of the NOR with heterochromatic blocks (repetitive DNA) in L. elongatus, which could act as a determinative element in the establishment of this process.

Transcriptional Activity of Translocated NORs in Barley (Hordeum VulgareL.)

“…As a whole, our results affirm that rRNA gene transcription is tightly regulated in order to provide the proper amount of rRnA for ribosome assembly (17,36,49) and also that nucleolar dominance is a regulatory process that controls the effective dosage of rRnA genes (17,43,44).…”

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

“…Alternatively, such variations may reflect the effect of partial nucleolar dominance in which the NOR of one of the parentals is active while the other one is inactive. This phenomenon is commonly observed in interspecific hybrids and has been described in Drosophila (Durica and Krider, 1978), Xenopus (Reeder and Roan, 1984) and, more recently, in fish (Gold et al , 1991; Hashimoto et al , 2009). …”

Cytogenetic Mapping of H1 Histone and Ribosomal RNA Genes in Hybrids between Catfish Species <b><i>Pseudoplatystoma corruscans</i></b> and <b><i>Pseudoplatystoma reticulatum</i></b>

“…Interspecific fish hybrids are important models for cytogenetic studies because they inherit 1 chromosome set of each parental species, which allows the identification of differences and/or similarities between the chromosomes of the parental species [Porto-Foresti et al, 2008;Hashimoto et al, 2009a] including sex chromosomes [Hashimoto et al, 2009b]. The fish hybrid between the species Pseudoplatystoma corruscans and P. reticulatum , known under the vernacular name 'ponto e vírgula', has great economic importance in the Brazilian aquaculture [Campos, 2010].…”