Abstract
Subtelomeric domains immediately adjacent to telomeres represent one of the most dynamic and rapidly evolving regions in eukaryotic genomes. A common feature associated with subtelomeric regions in different eukaryotes is the presence of long arrays of tandemly repeated satellite sequences. However, studies on molecular organization and evolution of subtelomeric repeats are rare. We isolated two subtelomeric repeats, CL14 and CL34, from potato (Solanum tuberosum). The CL14 and CL34 repeats are organized as independent long arrays, up to 1-3 Mb, of 182 bp and 339 bp monomers, respectively. The CL14 and CL34 repeat arrays are directly connected with the telomeric repeats at some chromosomal ends. The CL14 repeat was detected at the subtelomeric regions among highly diverged Solanum species, including tomato (Solanum lycopersicum). In contrast, CL34 was only found in potato and its closely related species. Interestingly, the CL34 repeat array was always proximal to the telomeres when both CL14 and CL34 were found at the same chromosomal end. In addition, the CL34 repeat family showed more sequence variability among monomers compared with the CL14 repeat family. We conclude that the CL34 repeat family emerged recently from the subtelomeric regions of potato chromosomes and is rapidly evolving. These results provide further evidence that subtelomeric domains are among the most dynamic regions in eukaryotic genomes.
Highlights
Subtelomeric domains immediately adjacent to telomeres represent one of the most dynamic and rapidly evolving regions in eukaryotic genomes
Identification of two subtelomeric repeats in potato Subtelomeric satellite repeats were identified by bioinformatic analysis of 1.24 million 454 Roche sequence reads generated from a homozygous diploid potato clone, DM1-3 (2n = 2x = 24), which was derived from chromosome doubling of a monoploid
The close physical association of these repeats with telomeres was demonstrated by either fiber-fluorescence in situ hybridization (FISH) (Cheng et al 2001; Zhong et al 1998; Dechyeva and Schmidt 2006; Sykorova et al 2003) or by repeat junction cloning and sequencing (Fajkus et al 1995; Sykorova et al 2003)
Summary
Subtelomeric domains immediately adjacent to telomeres represent one of the most dynamic and rapidly evolving regions in eukaryotic genomes. The presence of long arrays of tandemly repeated satellite sequences is a common feature associated with subtelomeric regions of many eukaryotic chromosomes. The chromosomal ends of Alliaceae species consist of highly repetitive satellite repeats, which structurally resemble the subtelomeric repeats found in other plant species These satellite repeats were proposed to replace the function of telomeric DNA in stabilizing the chromosomal ends (Pich et al 1996). An in-depth study of the structure and organization of subtelomeric repeats has been done in only a few species (Cheng et al 2001; Dechyeva and Schmidt 2006; Zhong et al 1998) Most importantly, it remains largely unknown how these repeats emerged and evolved during evolution. We report the evolutionary history of these two repeats in a set of diverged Solanum species
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