Comparative analysis of the composition of DNA pericentromeric heterochromatin chromosomes of Drosophila orena and Drosophila virilis (Diptera: Drosophilidae)

It is known that DNA sequences associated with heterochromatin are difficult for sequencing and subsequent analysis because of repeats enrichment. So, even finished and published genome sequencing projects of different organisms only contain information about the DNA sequences associated with euchromatin. Now, however, it is clear that understanding the principles of the eukaryotic genome functioning requires detailed information on the composition of its sequences. It should be noted that a comparative analysis of DNA in heterochromatin both phylogenetically close and distant taxa is relevant from the point of view of the problem of the evolution of genomes. Previously, we obtained region-specific DNA library chromocenter of polytene chromosomes of D. orena by microdissection. Next, on its basis we got a set of DNA clones and carried out their sequencing. The analysis of the clones using various software packages allowed to find out a wide variety of repetitive sequences among them (mobile genetic elements; tandem repeats) and the identified sequences homologous to the protein-coding genes. In addition, using microdissection method we obtained a region-specific DNA library chromocenter of polytene chromosomes of D. virilis. As part of this work, we carried out dot blot hybridization region-specific DNA libraries from the chromocenter D. virilis with characterized and annotated 42 DNA clones chromocenter D. orena. That allowed us to obtain new data on the molecular composition of DNA chromocenter D. virilis and estimate, generally, conservative composition of pericentromeric heterochromatin DNA in these relatively distant in the phylogenetic relation to species like D. orena and D. virilis. It should be noted that of 42 examined clones, only 8 failed to detect clones in the polytene chromosome DNA chromocenter D. virilis. Thus, it is established that, despite the evolutionary distance D. orena and D. virilis, DNA pericentromeric heterochromatin of polytene chromosomes in these species contains a significant amount of common sequences such as dispersed repeats (mobile genetic elements) − LTR-retrotransposons, LINE-elements, DNA transposons, tandem repeats (minisatellites), and sequences homologous to the protein-encoding genes (the genes, apparently, belong to the so-called orthologs).

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