Research Article |
Corresponding author: Cristian Araya-Jaime ( cristian.arayaj3@userena.cl ) Academic editor: Kenji Saitoh
© 2020 Cristian Araya-Jaime, Claudio Palma-Rojas, Elisabeth Von Brand, Alfonso Silva.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Araya-Jaime C, Palma-Rojas C, Von Brand E, Silva A (2020) Cytogenetic characterization, rDNA mapping and quantification of the nuclear DNA content in Seriolella violacea Guichenot, 1848 (Perciformes, Centrolophidae). Comparative Cytogenetics 14(3): 319-328. https://doi.org/10.3897/CompCytogen.v14i3.53087
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Seriolella violacea Guichenot, 1848 is an important component of the fish fauna of the Chilean coast and is of great economic interest. Cytogenetic information for the family Centrolophidae is lacking and the genomic size of five of the twenty-eight species described for this family are is barely known. This study aimed to describe for the first time the karyotype structure via classical and molecular cytogenetics analysis with the goal of identifying the constitutive heterochromatin distribution, chromosome organization of rDNA sequences and quantification of nuclear DNA content. The karyotype of S. violacea is composed of 48 chromosomes, with the presence of conspicuous blocks of heterochromatin on chromosomal pairs one and two. FISH assay with a 5S rDNA probe, revealed the presence of fluorescent markings on the heterochromatic block of pair one. The 18S rDNA sites are located exclusively on pair two, characterizing this pair as the carrier of the NOR. Finally, the genomic size of S. violacea was estimated at 0.59 pg of DNA as C-value. This work represents the first effort to document the karyotype structure and physical organization of the rDNA sequences in the Seriolella genome, contributing with new information to improve our understanding of chromosomal evolution and genomic organization in marine perciforms.
chromosomal statis, CMA3 staining, genome size, Repetitive DNAs
In recent years fish cytogenetics has accumulated data that establish evolutionary trends, phylogenetic relationships among different families, species and populations (
Seriolella violacea (Guichenot, 1848) is an important component of the fish fauna of the Chilean coast and has great economic value (
No cytogenetic information is available for the family Centrolophidae, and the chromosomal constitution of the 28 species described in this family is unknown (
Considering the absence of cytogenetic information on the Centrolophidae and the biological and economic importance of these pelagic fish, this study aims to describe for the first time the karyotype structure using classical and molecular cytogenetics analysis and quantification of nuclear DNA content in Seriolella violacea.
Six individuals, four males and two females, of S. violacea were obtained from the Laboratorio Central de Cultivos Marinos belonging to the Universidad Católica del Norte, Coquimbo-Chile. Mitotic chromosomes were obtained from cell suspensions of the anterior kidney, following the protocol established by
The 18S rDNA and the 5S rDNA probes were obtained by PCR (Polymerase Chain Reaction) from genomic DNA of Seriolella violacea using primers NS1F(5’-GTAGTCATATGCTTGTCTC-3’), and NS8R(5’-TCCGCAGGTTCACCTACGGA-3’) (
FISH was performed under high stringency conditions using the method described by
Measurements of nuclear DNA content (C-value) were done by microdensitometry in erythrocytes obtained from adult specimens (2♀ and 2♂), analyzing 200 nuclei per sample, using the software Image Pro-Plus 4.0. (Media Cybernetics). The blood was dispersed on slides, air dried, fixed in methanol-acetic acid (3:1 v/v) at 4 °C for 24 h and stained with the Feulgen reaction (
The karyotype of S. violacea shows 24 pairs of chromosomes (2n = 48; FN = 48), all acrocentric (Fig.
Conventional Giemsa-stained (A) and C-banding (B) in Seriolella violacea. Scale bar: 10 µm.
Dual FISH detected 18S and 5S rDNA probes on different chromosome pairs (Fig.
Karyotypes of Seriolella violacea after CMA3 staining (A) and dual color FISH with 18S rDNA (green) and 5S rDNA (red) probes (B). Scale bar: 10 µm.
Finally, the nuclear DNA content measured in erythrocytes of S. violacea was estimated to be 1.18 ± 0.04 pg (average IOD = 14345 arbitrary units), with a coefficient of variation of 4.2%. Since S. violacea is a diploid organism (2n = 48, n = 24), the C-value of 0.59 pg of DNA (Table
Known genomic sizes C-Value(pg) for representatives of the Centrolophidae family.
Species | C-Value | Method | Cell Type | St. Species | Reference |
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Centrolophus niger | 0.70 | FIA | RBC | BS, GD, OM, RP |
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Hyperoglyphe antarctica | 0.77 | FIA | RBC | BS, GD, OM, RP |
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Schedophilus huttoni | 0.76 | FIA | RBC | BS, GD, OM, RP |
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Seriolella punctata | 0.78 | FIA | RBC | BS, GD, OM, RP |
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Tubbia tasmanica | 0.76 | FIA | RBC | BS, GD, OM, RP |
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Seriolella violacea | 0.59 | FIA | RBC | GD, OM | in this work |
There are no data related to the organization of the repetitive fraction of the genome in the family Centrolophidae. Nevertheless, studies within the marine perciform order, specifically in representatives of the families Ephippidae, Serranidae, Lutjanidae, and Haemulidae have permitted the recognition of a diploid number of 48 chromosomes (completely acrocentric); the non-syntenic state of sequences 5S rDNA and 18S rDNA; and the presence of a single NOR, establishing this pattern as a plesiomorphic characteristic for marine perciforms (
Finally, 0.59 pg of DNA (C-value) measured in erythrocytes of S. violacea represents a significantly (20%) lower nuclear DNA content than that of the five species of the Centrolophipadae family analized (Table
In this work, the karyotype of a representative of the Centrolophidae family, S. violacea, is described for the first time. Its karyotype is made up of 48 acrocentric chromosomes (2n = 48; FN = 48), simple NOR and ribosomal cistrons (5S-18S rDNA) are not synthetic. Meanwhile, the nuclear DNA content, C-value, was found to be 0.59 pg. It is necessary to perform additional studies physically mapping repetitive DNAs in the other representatives of the genus Seriolella Guichenot, 1848, in order to understand the involvement of these sequences in the process of chromosomal evolution that these fish may be experiencing. It is especially necessary to analyze the chromosomal microstructure, given the chromosomal stasis that most marine perciforms present, as this will also expand knowledge of fish fauna which is facing serious conservation issues.
This study was funded through a research project from DGIP/ Universidad Católica del Norte 2010. CAJ: conceived the study, conducted the experiments, analysed the data and wrote the manuscript. CPR: conducted the experiments, analysed the data and manuscript revision. EVB: conducted the experiments, analysed the data and manuscript revision. AS: analysed the data and manuscript revision. All authors have read and approved the final version.