Pericentromeric location of the telomeric DNA sequences on the European grayling chromosomes

Abstract

The chromosomal characteristics, locations and variations of the C-band positive heterochromatin and telomeric DNA sequences were studied in the European grayling karyotype (Thymallus thymallus, Salmonidae) using conventional C-banding, endonucleases digestion banding, silver nitrate (AgNO3), chromomycin A3 and 4′,6-diamidino-2-phenylindole staining techniques as well as fluorescence in situ hybridization (FISH) and primed in situ labelling. Original data on the chromosomal distribution of segments resistant to AluI restriction endonuclease and identification of the C-banded heterochromatin presented here have been used to characterize the grayling karyotype polymorphism. Structural and length polymorphism of the chromosome 21 showing a conspicuous heterochromatin block adjacent to the centromere seems to be the result of the deletion and inversion. Two pairs of nuclear organizer regions (NOR)-bearing chromosomes were found to be polymorphic in size and displaying several distinct forms. FISH with telomeric peptide nucleic acid probe enabled recognition of the conservative telomeric DNA sequences. The karyotype of the thymallid fish is thought to experienced numerous pericentric inversions and internal telomeric sites (ITSs) observed at the pericentromeric regions of the six European grayling metacentric chromosomes are likely relics of the these rearrangements. None of the ITS sites matched either chromosome 21 or NOR bearing chromosomes.

Minute Y chromosomes and karyotype evolution in Madagascan iguanas (Squamata: Iguania: Opluridae)

“…Several explanations have been suggested for the emergence of ITSs without any conspicuous changes in karyotype. Such ITSs could reflect telomerase activity during the repair of double‐stranded breaks (Flint et al ., ; Azzalin, Nergadze & Giulotto, ), an association of telomeric‐like sequences with satellite repeats or mobile elements (Azzalin et al ., ; Rovatsos et al ., ), or they could be the remnants of ancestral intrachromosomal rearrangements such as inversions (Ocalewicz et al ., ). A high rate of intrachromosomal rearrangements despite a low rate of interchromosomal rearrangements was recently shown to be rather common in sauropsids (Alföldi et al ., ; Skinner & Griffin, ; Lithgow et al ., ; Rovatsos et al ., ; Johnson Pokorná et al ., ).…”

Cytogenetic identification of genomic elements of brook trout ( Salvelinus fontinalis ) in the karyotype of Arctic char ( Salvelinus alpinus ) from the aquaculture broodstock

“…For identification of AT‐rich chromatin regions, chromosomes were stained with 4,6‐diamidino‐2‐phenylindole (DAPI) using antifade solution Vectashield with 1.5 µg/ml DAPI (Vector, Burlingame, CA). Telomeric DNA repeats were detected by the fluorescence in situ hybridization (FISH) using a telomere PNA (Peptide Nucleic Acid) probe conjugated with FITC (DAKO, Denmark) according to the manufacturer's protocol with some modifications (Ocalewicz et al, ). Briefly, chromosomal DNA was denaturated at 85°C for 5 min under the coverslip in the presence of the telomere PNA probe.…”

The grayling genome reveals selection on gene expression regulation after whole genome duplication

“…Interestingly, the species within these two clades have also evolved widely different genome structures, ecology, physiology and life history adaptations (Hendry & Stearns 2004). In contrast to the Thymallus lineage, the species in the subfamily Salmoninae have fewer and highly derived chromosomes resulting from large-scale chromosomal translocations and fusions (Supplementary Figure S1), display extreme phenotypic plasticity, and have evolved the capability of migrating between fresh and saltwater habitats (referred to as anadromy) (Nygren et al 1971;Phillips & Ráb 2001;Hartley 1987;Ocalewicz et al 2013;Alexandrou et al 2013). This unique combination of both shared and lineage-specific rediploidization histories, and striking differences in genome structure and adaptations, provides an ideal study system for addressing key questions about the evolutionary consequences of WGD.…”