engleski

A novel, interspersed type of organization of satellite DNA in Tribolium madens heterochromatin

Analysis of arrangement of satellite DNA sequences in Tribolium madens (Insecta, Coleoptera) by Southern analysis of pulsed-field blots and two colour FISH on extended chromosomes and DNA fibers revealed a novel type of heterochromatin organization. Two satellite DNAs, distributed over the whole pericentromeric heterochromatin of all chromosomes form clusters, ranging in size from 150 kb up to several Mb. Within the clusters, both satellites are in the form of highly interspersed, short homogeneous arrays which vary in size with the lowest length limit of only few kb. The longest arrays composed of a single satellite are relatively short, up to 70 kb for satellite I, or up to 45 kb for satellite II. Only a small fraction of about 15% of satellite II is organized in long tandem repeats, while the rest is in a form of only few repeats intermingled with satellite I. The results indicate that large clusters composed of interspersed arrays of both satellites represent a major component of T. madens heterochromatin, which is mostly devoid of long regions of other sequences. The same organizational pattern probably also includes a region of the functional centromere. We propose that such organizational pattern of DNA sequences in heterochromatin might be common in genomes characterised by a high rate of interchromosomal exchange. This pattern of organization is different from that in other animal as well as in plant species analysed up to now, in which every satellite in heterochromatin is organized in a small number of large separate domains.

extended chromosomes; DNA fibers; Coleoptera; repetitve DNA

nije evidentirano