Comrapative analysis of inverted sequences of noncoding region in the mitochondrial DNA of the Baikal sponges (Fam. Lubomirskiidae)

Abstract

In recent years, mitochondrial DNA (mtDNA) has been used to solve many phylogenetic problems at different taxonomic levels. Previously, the nucleotide sequences of the mitochondrial genomes of the Baikal endemic sponge species of the Lubomirskiidae family have been identified. Their phylogenetic links are still being actively studied, and their systematics is considered to be not definitive. In order to study the mechanisms of speciation and evolution of mtDNA, special attention is paid to the investigations of noncoding DNA. We have studied the characteristics of the organization of the intergenic mtDNA regions in the Baikal sponges on the example of the longest region between the tRNA^Tyr and tRNA^Ile genes of the species L. baicalensis, S. papyracea, R. echinata, and B. intermedia profundalis. A comparative analysis of the sequences has shown the presence of secondary structures represented by individual hairpins and complex multilevel structures. Based on a comparative analysis of secondary structures, we have suggested their role as both regulative elements and potential mobile elements. We gave determined the continuity of these structures among representatives of different genera of the Lubomirskiidae family. The highest similarity in their distribution and localization was found in phylogenetically related species of the Baikal sponges.