engleski

Conserved satellite DNA sequences in the pericentromeric heterochromatin of tenebrionid beetles (Coleoptera, Insecta)

Pericentromeric heterochromatin, located on all chromosomes, makes a substantial portion of up to 50% of the genome in many tenebrionid beetles. Molecular and cytogenetical studies reveal tandemly repeated satellite DNAs as the major heterochromatic DNA components. Usually, a single highly abundant satellite DNA co-exists in the heterochromatin with a number of other, low copy number satellites. The same set of satellite sequences is present in related species and the satellites are differentially amplified among the species forming species-specific profiles. In five species of tenebrionid genus Palorus six unrelated satellite DNAs are found. Major, highly abundant satellite is organized in the form of long arrays regularly interspersed with the short stretches of low copy number satellites. Such type of organization encompasses the whole pericentromeric, as well as centromeric regions. The peculiar characteristic of Palorus satellite DNAs is their extremely slow sequence evolution resulting in the absence of divergence and species diagnostic mutations. Complete sequence conservation is detected among the species within the genus as well beyond the level of genus, despite separation for 50-60 Myr. This unexpectedly high conservation might be induced by a bias in turnover mechanisms favouring the ancestral sequence in the process of molecular drive. Selective pressure on Palorus satellite DNA sequences can be also suggested. This could be related to their possible role in the formation of chromatin structure characteristic for pericentromeric and centromeric regions.

satellite DNA; heterochromatin; evolution

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