Autosomal localization of interstitial telomeric sites (ITS) in brook trout, <i>Salvelinus fontinalis</i> (Pisces, Salmonidae)

Abstract

Cytogenetic analysis of brook trout performed with molecular and conventional methods led to identification of interstitial telomeric sites on one or two subtelocentric chromosomes within the same pair. Morphology and specific patterns of these chromosomes using fluorochromes associated with A/T- or G/C-rich DNA proved that these chromosomes are not sex related. The chromomycin-positive region was located on the short arms of the ITS bearing chromosome pair and flanked by telomeric sequences, suggesting that this part of the chromosome had been translocated from another one. Our observations confirm that GC-rich regions are highly mobile genetic structures, and led to ITS formation on brook trout chromosomes.

Distribution of Telomeric DNA Sequences on the X-Radiation-Induced Chromosome Fragments Observed in the Genome of Androgenetic Brook Trout (<b><i>Salvelinus fontinalis</i></b>, Mitchill 1814)

“…Presumably, chromosome fragments with 2 interstitially located telomeric signals were also ring chromosomes as the fusion of a radiation-broken chromosome with the opposite telomeric region has been described previously [Henegariu et al, 1997;Fortin et al, 2009]. However, we do not exclude that some of these fragments might have originated from the brook trout chromosomes with interstitially located telomeric DNA sequences [Ocalewicz et al, 2004b]. Chromosome fragments, showing 2 always terminally located telomeres, represented another chromatin arrangement.…”

Cytogenetic and histological studies of the brook trout, Salvelinus fontinalis (Mitchill), and the Arctic char, S. alpinus (L.) hybrids

“…Both parental char species of the hybrids studied here show genetic sex determination (Woram et al 2003), but probably, their sex chromosomes are at different stages of the morphological differentiation. Indeed, brook trout putative sex chromosomes are two medium-sized metacentric chromosomes (Phillips et al 2002;Ocalewicz et al 2004), while Arctic char sex-linked microsatellite DNA sequences have been mapped to one of the largest metacentric chromosome pair (Kwitkowski 2007). Thus, interactions between brook trout and Arctic char sex chromosomes and genes from the sex chromosomes and autosomes rather than unpairing of the parental chromosomes may affect gonadal development in the hybrids.…”

“…Individuals from the brook trout broodstock are characterized by a diploid chromosome number (2n) and a chromosome arm number, FN (Fundamental Number), which are 84 and 100, respectively (Ocalewicz et al 2004). In the Arctic char individuals from Rutki broodstock, diploid chromosome number varies from 81 to 82 (FN = 100) (Pomianowski et al 2012).…”

Genomic Distribution of Telomeric DNA Sequences – What Do We Learn from Fish About Telomere Evolution?

“…Chromosome fragment with two interstitially located telomeric signals observed in the androgenetic brook trout (Figure 2c) might have been also ring chromosome formed in the course of fusion of a radiation-broken chromosome arm with the opposite unbroken arm or arm broken within telomeric region (Henegariu et al, 1997). However we do not exclude that this fragment might have originated from one of the brook trout chromosomes with interstitially located telomeric DNA sequences (Ocalewicz et al, 2004b). Chromosome fragments showing two, always terminally located telomeres detected in the androgenetic brook trout represented another chromatin arrangements (Figure 2d).…”

“…Other mechanisms leading to the ITS formation have been suggested in three Salvelinus species: lake trout (Salvelinus namaycush), brook trout (Salvelinus fontinalis) and the Arctic charr (Salvelinus alpinus) showing subterminal position of the interstitial telomeric sequences (Figure 1c-d) assigned to the vicinity of the CMA 3 positive GC-rich heterochromatin (Reed and Phillips, 1995;Ocalewicz et al, 2004b;Pomianowski et al, 2012). Guanine-rich chromosomal regions are involved in several rearrangements like transpositions, duplications and (or) translocations resulted in multichromosomal location and variation in size of CMA 3 positively stained chromatin in Salvelinus species (Phillips et al, 1988;Phillips and Ráb, 2001).…”