Cloning, identification and characterization of a repetitive sequence flanking telomere and homologous to canrep in Brassica napus.

Satellite DNAs consist of long tandem arrays of short or large repeated sequences that form the centromeric and sometimes also subtelomeric regions of all higher eukaryote chromosomes. Telomeres and centromeres are the most important elements involved in the structure and function of chromosome. Telomeric DNA sequences are conserved among nearly all plant species. Although centromere-specific DNA sequences have been isolated in a wide range of plant species, almost no conservation was found in their DNA sequences. Here, we utilized the cassette-ligation-mediated PCR approach for cloning the sequence near the telomeric repeats of Brassica napus. Sequences analysis showed that one sequence was highly homologous to the centromeric satellite DNA sequence reported. FISH revealed that this satellite was located primarily at centromeric regions of most chromosomes, and also at some chromosome ends. The sequence was a subtelomeric satellite DNA which possessed variability in the evolution of chromosomes of Brassica species. The phylogenetic tree analysis of the satellite showed its sequence was conservative in Brassica. We discussed why the centromeric satellites appeared in the subtelomeric region. [ABSTRACT FROM AUTHOR]