Terminal heterochromatin and alternative telomeric sequences in Allium cepa.
The chromosome termini of the onion (Allium cepa) apparently lack Arabidopsis-type telomeric repeats. The terminal Giemsa bands of A. cepa chromosomes contain a 375-bp satellite and (short arm of chromosome 8)/ or (short arm of chromosome 6) rDNA repeats. By means of fluorescence in situ hybridization (FISH) on metaphase chromosomes and on DNA fibres with probes specific for Ty1-copia retroelements and a En/Spm-transposable element-like sequence, respectively, it was demonstrated that the former are rarely and the latter frequently associated with satellite repeats within the terminal heterochromatin. Polymerase chain reaction of polyC-tailed nuclear DNA with anchor primers and single satellite-specific primers yielded amplification products that, after cloning and sequencing, revealed satellite sequences. This supports the idea that satellite repeats represent one class of terminal sequences in A. cepa.
Pich
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U
Institut für Pflanzengenetik und Kulturpflanzenforschung, Gatersleben, Germany.
Schubert
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I
D000490:Allium / Q000235:genetics*; D001483:Base Sequence; D015139:Blotting, Southern; D015342:DNA Probes; D018745:Genome, Plant; D006570:Heterochromatin / Q000235:genetics*; D017404:In Situ Hybridization, Fluorescence; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012091:Repetitive Sequences, Nucleic Acid; D018626:Retroelements; D016615:Telomere / Q000235:genetics*
D015342:DNA Probes; D006570:Heterochromatin; D018626:Retroelements