engleski

Comparative study of satellite DNAs from the genus Tribolium

Highly abundant satellite DNAs from four Tribolium (Coleoptera, Insecta) species: T. castaneum, T. confusum, T. freemani and T. madens were cloned and sequenced. The satellites comprise from 17% to 35% of the corresponding genomic DNA. In T. madens, two related satellite DNAs are present having complex monomer sequence of 225 and 711 bp. They were created from a common subsequence, approx. 100 bp long, through the processes of duplication and inversion followed by sequence divergence. Other three species have a single satellites of a unique sequence and monomer lengths of 166 bp for T. freemani, 360 bp for T. castaneum and 158 bp for T. confusum satellite. The satellites have high A+T contents from 70% to 75%, they are rich in inverted repeats and are evenly distributed in the regions of centromeric heterochromatin of all chromosomes, as shown by a fluorescent in situ hybridization. Pairwise comparison of satellites from different Tribolium species reveals the highest sequence similarity of 47.1% between the satellites from the sibling species T. freemani and T. castaneum. The phylogenetic relationships among Tribolium species deduced from satellite sequences agree with those based on karyological, chemotaxonomic and hybridization data. This indicates a parallel in the divergence of satellites and some genetical and cytogenetical characters. Despite low mutual sequence similarity which makes them species specific, Tribolium satellites have a common structural characteristic: a block of about 95% A+T content, 20 to 42 bp long, flanked at one side by an inverted repeat which can potentially form a thermodinamically stable dyad structure. Since similar structural features are found in centromeric DNA of Saccharomyces cerevisiae and Chironomus pallidivittatus, their possible importance in centromere function may be inferred.

satellite DNA; evolution; speciation; phylogeny; centromere

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