SOME FEATURES OF THE BAIKAL SPONGE MITOCHONDRIAL GENOME ORGANIZATION | Vestnik Tomskogo gosudarstvennogo universiteta – Tomsk State University Journal. 2010. № 341.

SOME FEATURES OF THE BAIKAL SPONGE MITOCHONDRIAL GENOME ORGANIZATION

Sponge fauna in Lake Baikal includes the families Lubomirskiidae and Spongillidae. The family Lubomirskiidae is endemic, and includes 4 genera and 13 species and 1 subspecies (Efremova, 2004). The taxonomy of freshwater sponges, in particular the Lubomirskiidae, is problematic and their phylogeny and evolution are not well understood. During the last years many scientists start to analyse the mitochondrial genome to solve these issues. Moreover, recently a sequence of the mitochondrial genome of the Baikal sponge Lubomirskia baicalensis was determined (Lavrov, 2010). At present, the study of non-coding regions of mtDNA sponges is of great scientific interest because its mechanism of regulation of replication and transcription is still unknown. The nucleotide sequences of the intergenic regions (IGR) of the mitochondrial genome between the genes tRNA-Tyr - tRNA-Ile and tRNA-Ile - tRNA-Met of 20 sponges from the family Lubomirskiidae were determined. The length of these sequences ranges from 475 bp to 908 bp, which is associated with the presence of multiple indels. Three sponges were chosen for a more detailed comparative analysis, the representatives of 3 genera of the family Lubomirskiidae: L. baicalensis, B. intermedia profundalis and S. papyracea. The analysis of these sequences has shown many inverted repeats that form secondary structures. Some of these secondary structures were previously identified in Lubomirski baicalensis by D.V. Lavrov. The IGRs of all the analysed Baikal sponge have A-T-rich regions localized before tRNA genes, which form a stable hairpin, similar in all sponges. We have also found an unknown open reading frame (ORF) between the tRNA-Tyr and tRNA-Ile genes of mitochondrial genome of sponges from the family Lubomirskiidae. This ORF encodes the putative protein, which has the length ranging from 38 aa to 74 aa. All amino acid sequences possess the start ATG-codon (at position 28) and the stop-codons UAG or UAA at different positions. Despite the different length of the putative protein, it has 21 amino acids conservative region at the N-end, which is a part of putative transmembrane domain. Our study showed that increase of the size of intergenic regions of the mitochondrial genome of the Baikal sponge occurs not only due to the insertion of direct and inverted repeats, but also due to presence of the open reading frames. Thus the Baikal endemic sponges differ from cosmopolitan sponges in their features of the mitochondrial genome organization.

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Keywords

губки, Lubomirskiidae, митохондриальный геном, открытая рамка считывания, sponges, Lubomirskiidae, mitochondrial genome, open reading frame

Authors

Name	Organization	E-mail
Maikova Olga O.	Limnological Institute, SB RAS (Irkutsk)	idboo8@mail.ru
Belikov Sergey I.	Limnological Institute, SB RAS (Irkutsk)

Всего: 2

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