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.
Institut für Pflanzengenetik und Kulturpflanzenforschung, Gatersleben, Germany.
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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