engleski

Satellite DNA sequences "frozen" during the evolution of some insect species

The intriguing diversity of highly abundant satellite repeats found even among closely related species can result from processes leading to dramatic changes in copy number of a particular sequence in the genome and not from rapid accumulation of mutations. To test this hypothesis, we investigated the distribution of two satellite DNAs, PRAT and PSUB, both highly abundant in coleopteran species <Palorus ratzeburgii> and <Palorus subdepressus>, respectively, in eight species belonging to related genera (<Tribolium>, <Tenebrio>, <Latheticus>), subfamily (Pimeliinae) and family (Chrysomelidae). PRAT satellite, in low-copy number, was present in all tested species, while PSUB was not detected in two out of eight species. The PRAT satellite detected in <Pimelia elevata> has been sequenced, and compared with PRAT monomers from <Palorus ratzeburgii> and <Palorus subdepressus>. Although the two <Palorus> species diverged at least 7 Myr ago, and subfamily Pimeliinae separated from the genus <Palorus> 50-60 Myr ago, no species diagnostic mutations were detected. The same was found true for the PSUB cloned from <Palorus subdepressus> and <Tribolium madens>. This unexpectedly high conservation of satellite DNA sequences could most likely be induced by a small bias of turnover mechanisms favouring the ancestral sequence in the process of molecular drive.

evolution; satellite DNA; heterochromatin

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