Molecular organization of terminal repetitive DNA

Authors: Daryna Dechyeva Thomas Schmidt

Publish Date: 2007/01/19

Volume: 14, Issue: 8, Pages: 881-897

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Abstract

We have isolated families of subtelomeric satellite DNA sequences from species of four sections of the genus Beta and from spinach a related Chenopodiaceae Twentyfive clones were sequenced and representative repeats of each family were characterized by Southern blotting and FISH The families of ApaI restriction satellite repeats were designated pAv34 pAc34 the families of RsaI repeats pRp34 pRn34 and pRs34 The repeating units are 344–362 bp long and 457–988 homologous with a clear speciesspecific divergence Each satellite monomer consists of two subrepeats SR1 and SR2 of 165–184 bp respectively The repeats of each subrepeat group are highly identical across species but share only a homology of 408–548 with members of the other subrepeat group Two evolutionary steps could be supposed in the phylogeny of the subtelomeric satellite family the diversification of an ancestor satellite into groups representing SR1 and SR2 in the progenitor of Beta and Spinacea species followed by the dimerization and diversification of the resulting 360 bp repeats into sectionspecific satellite DNA families during species radiation The chromosomal localization of telomeric subtelomeric and rDNA tandem repeats was investigated by multicolour FISH Highresolution analysis by fibre FISH revealed a unique physical organization of B vulgaris chromosome ends with telomeric DNA and subtelomeric satellites extending over a maximum of 63 kb and 125 kb respectively

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