Heterochromatin distribution and structure in<i>Gymnothorax unicolor</i>(Anguilliformes, Muraenidae)

Salvadori, Susanna; Deiana, Anna Maria; Coluccia, Elisabetta; Cannas, Rita; Cau, Angelo; Milia, A

doi:10.1080/11250009709356184

Cited by 6 publications

(10 citation statements)

References 19 publications

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“… 22 , 23 The pattern of heterochromatin distribution is known for eight Muraenidae species; these few available data indicate the presence of centromeric heterochromatic blocks in almost all species; furthermore, large bands in pericentromeric and/or interstitial position are present in some species. 20 , 22 , 24 The nucleolus organizer regions (NOR) were localized by silver staining on one chromosome pair in all species studied; furthermore, fluorescence in situ hybridization (FISH) mapping of major ribosomal genes and telomeric sequences was carried out in M. helena and G. tile . 18 , 25 , 26 In addition, two repetitive DNA fractions from the M. helena genome, were isolated, physically mapped and compared to G. unicolor .…”

Section: Introductionmentioning

confidence: 99%

Identification of two new repetitive elements and chromosomal mapping of repetitive DNA sequences in the fish Gymnothorax unicolor (Anguilliformes: Muraenidae)

et al. 2011

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Muraenidae is a species-rich family, with relationships among genera and species and taxonomy that have not been completely clarified. Few cytogenetic studies have been conducted on this family, and all of them showed the same diploid chromosome number (2n=42) but with conspicuous karyotypic variation among species. The Mediterranean moray eel Gymnothorax unicolor was previously cytogenetically studied using classical techniques that allowed the characterization of its karyotype structure and the constitutive heterochromatin and argyrophilic nucleolar organizer regions (Ag-NORs) distribution pattern. In the present study, we describe two new repetitive elements (called GuMboI and GuDdeI) obtained from restricted genomic DNA of G. unicolor that were characterized by Southern blot and physically localized by in situ hybridization on metaphase chromosomes. As they are highly repetitive DNA sequences, they map in heterochromatic regions. However, while GuDdeI was localized in the centromeric regions, the GuMboI fraction was distributed on some centromeres and was co-localized with the nucleolus organizer region (NOR). Comparative analysis with other Mediterranean species such as Muraena helena pointed out that these DNA fractions are species-specific and could potentially be used for species discrimination. As a new contribution to the karyotype of this species, we found that the major ribosomal genes are localized on acrocentric chromosome 9 and that the telomeres of each chromosome are composed of a tandem repeat derived from a poly-TTAGGG DNA sequence, as it occurs in most vertebrate species. The results obtained add new information useful in comparative genomics at the chromosomal level and contribute to the cytogenetic knowledge regarding this fish family, which has not been extensively studied.

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Section: Introductionmentioning

confidence: 99%

Identification of two new repetitive elements and chromosomal mapping of repetitive DNA sequences in the fish Gymnothorax unicolor (Anguilliformes: Muraenidae)

et al. 2011

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“…The occurrence of pericentric inversions involving the ribosomal clusters could explain the change of the NOR position from the terminal to the interstitial, as already demonstrated between M. helena and G. unicolor (Salvadori et al, 1997(Salvadori et al, , 2003. Moreover, the heterochromatin associated with the NOR could have contributed to the translocation of rDNA sites in many species, as demonstrated in other teleosts (Gornung, 2013).…”

Section: Discussionmentioning

confidence: 58%

“…For most species in this study, a large amount of constitutive heterochromatin was detected with species‐specific C‐banding patterns that enabled pairing of the homologous chromosomes. The presence of large heterochromatic blocks, mainly localized in the pericentromeric and telomeric positions, appears to be a common feature in the Muraenidae (Cau et al , ; Salvadori et al , , ; Porto‐Foresti et al , ; Vasconcelos & Molina, ; Alves et al , ). The variations in quantity, position and properties of the heterochromatin suggest that the constitutive heterochromatin could play an important role in the karyotype evolution of the Muraenidae, as previously demonstrated for the Cyprinidae (Ueda et al , ).…”

Section: Discussionmentioning

confidence: 99%

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Comparative cytogenetics of six Indo‐Pacific moray eels (Anguilliformes: Muraenidae) by chromosomal banding and fluorescence in situ hybridization

Coluccia

Deidda

Cannas

et al. 2015

Journal of Fish Biology

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A comparative cytogenetic analysis, using both conventional staining techniques and fluorescence in situ hybridization, of six Indo-Pacific moray eels from three different genera (Gymnothorax fimbriatus, Gymnothorax flavimarginatus, Gymnothorax javanicus, Gymnothorax undulatus, Echidna nebulosa and Gymnomuraena zebra), was carried out to investigate the chromosomal differentiation in the family Muraenidae. Four species displayed a diploid chromosome number 2n = 42, which is common among the Muraenidae. Two other species, G. javanicus and G. flavimarginatus, were characterized by different chromosome numbers (2n = 40 and 2n = 36). For most species, a large amount of constitutive heterochromatin was detected in the chromosomes, with species-specific C-banding patterns that enabled pairing of the homologous chromosomes. In all species, the major ribosomal genes were localized in the guanine-cytosine-rich region of one chromosome pair, but in different chromosomal locations. The (TTAGGG)n telomeric sequences were mapped onto chromosomal ends in all muraenid species studied. The comparison of the results derived from this study with those available in the literature confirms a substantial conservation of the diploid chromosome number in the Muraenidae and supports the hypothesis that rearrangements have occurred that have diversified their karyotypes. Furthermore, the finding of two species with different diploid chromosome numbers suggests that additional chromosomal rearrangements, such as Robertsonian fusions, have occurred in the karyotype evolution of the Muraenidae.

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“…Usually, the 18S rDNA occupies a terminal position in chromosomes, in contrast to the more frequent interstitial position of the 5S rDNA ( Sochorová et al , 2018 ). All the Osteochilus species under study had both ribosomal classes located in a terminal position in association with heterochromatin, suggesting that these regions were recombination hotspots ( Salvadori et al , 1997 ; Sola et al , 2003 ; Gornung, 2013 ). Their terminal position may also facilitate the dispersion of these sequences to other chromosomes, according to Rabl’s model, since higher recombination rates were found near the telomeric region (reviewed in Foster and Bridger, 2005 ).…”

Section: Discussionmentioning

confidence: 99%

Chromosomes of Asian cyprinid fishes: Variable karyotype patterns and evolutionary trends in the genus Osteochilus (Cyprinidae, Labeoninae, “Osteochilini”)

et al. 2020

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The Cyprinidae family is a highly diversified but demonstrably monophyletic lineage of cypriniform fishes. Among them, the genus Osteochilus contains 35 recognized valid species distributed from India, throughout Myanmar, Laos, Thailand, Malaysia, Indonesian archipelago to southern China. In this study, karyotypes and other chromosomal characteristics of five Osteochilus species occurring in Thailand, namely O. lini, O. melanopleura, O. microcephalus, O. vittatus and O. waandersii were examined using conventional and molecular cytogenetic protocols. Our results showed they possessed diploid chromosome number (2n) invariably 2n = 50, but the ratio of uni-and bi-armed chromosomes was highly variable among their karyotypes, indicating extensive chromosomal rearrangements. Only one chromosome pair bearing 5S rDNA sites occurred in most species, except O. melanopleura, where two sites were detected. In contrast, only one chromosomal pair bearing 18S rDNA sites were observed among their karyotypes, but in different positions. These cytogenetic patterns indicated that the cytogenomic divergence patterns of these Osteochilus species were largely corresponding to the inferred phylogenetic tree. Similarly, different patterns of the distributions of rDNAs and microsatellites across genomes of examined species as well as their different karyotype structures indicated significant evolutionary differentiation of Osteochilus genomes.

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Heterochromatin distribution and structure inGymnothorax unicolor(Anguilliformes, Muraenidae)

Cited by 6 publications

References 19 publications

Identification of two new repetitive elements and chromosomal mapping of repetitive DNA sequences in the fish Gymnothorax unicolor (Anguilliformes: Muraenidae)

Identification of two new repetitive elements and chromosomal mapping of repetitive DNA sequences in the fish Gymnothorax unicolor (Anguilliformes: Muraenidae)

Comparative cytogenetics of six Indo‐Pacific moray eels (Anguilliformes: Muraenidae) by chromosomal banding and fluorescence in situ hybridization

Chromosomes of Asian cyprinid fishes: Variable karyotype patterns and evolutionary trends in the genus Osteochilus (Cyprinidae, Labeoninae, “Osteochilini”)

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