Satellite DNA of the red flour beetle Tribolium castaneum - Comparative study of satellites from the genus Tribolium

A highly abundant satellite DNA comprising 17% of the Tribolium castaneum (Insecta, Coleoptera) genome was cloned and sequenced. The satellite monomer is 360 bp long, has a high A+T content of 73%, and lacks significant internal substructures. The sequence variability is 3.6%, essentially due to random distribution of single-point mutations. The satellite is evenly distributed in the regions of centromeric heterochromatin of all 20 chromosomes, as shown by fluorescent in situ hybridization. Comparison of T. castaneum satellite with those from three different but congeneric species reveals the highest sequence similarity of 47.1% with the satellite from the sibling species Tribolium freemani. The phylogenetic relationships among Tribolium species deduced from satellite sequence agree with those based on karyological, chemotaxonomic, and hybridization data. This indicates a parallel in the divergence of satellites and some genetic and cytogenetic 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 thermodynamically 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.