RESUMO
The taxonomy of the genus Saccostrea is very confused, however, there is relatively little molecular information available on Saccostrea. In this study, we determined and described for the first time the complete mitochondrial genome of Saccostrea malabonensis. The complete mitogenome of S. malabonensis is 16,204 bp in length, containing 12 protein-coding genes (lack of atp8 gene), two rRNA genes, 23 tRNA genes. The overall nucleotide composition of S. malabonensis has an AT content of 61.94% (26.29% A, 15.71% C, 22.35% G, 35.65% T). Phylogenetic analyses showed that S. malabonensis is first clustered with S. cucullata then united with Saccostrea kegaki.
RESUMO
Complete mitochondrial genomes play important roles in studying genome evolution, phylogenetic relationships, and species identification. Sea cucumbers (Holothuroidea) are ecologically important and diverse members, living from the shallow waters to the hadal trench. In this study, we present the mitochondrial genome sequence of the sea cucumber Benthodytes marianensis collected from the Mariana Trench. To our knowledge, this is the first reported mitochondrial genome from the genus Benthodytes. This complete mitochondrial genome is 17567 bp in length and consists of 13 protein-coding genes, two ribosomal RNA genes and 22 transfer RNA genes (duplication of two tRNAs: trnL and trnS). Most of these genes are coded on the positive strand except for one protein-coding gene (nad6) and five tRNA genes which are coded on the negative strand. Two putative control regions (CRs) have been found in the B. marianensis mitogenome. We compared the order of genes from the 10 available holothurian mitogenomes and found a novel gene arrangement in B. marianensis. Phylogenetic analysis revealed that B. marianensis clustered with Peniagone sp. YYH-2013, forming the deep-sea Elasipodida clade. Positive selection analysis showed that eleven residues (24 S, 45 S, 185 S, 201 G, 211 F and 313 N in nad2; 108 S, 114 S, 322 C, 400 T and 427 S in nad4) were positively selected sites with high posterior probabilities. We predict that nad2 and nad4 may be the important candidate genes for the further investigation of the adaptation of B. marianensis to the deep-sea environment.
Assuntos
Genoma Mitocondrial , Pepinos-do-Mar/genética , Aclimatação , Animais , Composição de Bases , DNA Mitocondrial/genética , Ordem dos Genes , Proteínas Mitocondriais/genética , Filogenia , RNA Ribossômico/genética , RNA de Transferência/genética , Pepinos-do-Mar/fisiologia , Seleção GenéticaRESUMO
Starfish (phylum Echinodermata) are ecologically important and diverse members of marine ecosystems in all of the world's oceans, from the shallow water to the hadal zone. The deep sea is recognized as an extremely harsh environment on earth. In this study, we present the mitochondrial genome sequence of Mariana Trench starfish Freyastera benthophila, and this study is the first to explore in detail the mitochondrial genome of a deep-sea member of the order Brisingida. Similar to other starfish, it contained 13 protein-coding genes, two ribosomal RNA genes, and 22 transfer RNA genes (duplication of two tRNAs: trnL and trnS). Twenty-two of these genes are encoded on the positive strand, while the other 15 are encoded on the negative strand. The gene arrangement was identical to those of sequenced starfish. Phylogenetic analysis showed the deep-sea Brisingida as a sister taxon to the traditional members of the Asteriidae. Positive selection analysis indicated that five residues (8 N and 16 I in atp8, 47 D and 196 V in nad2, 599 N in nad5) were positively selected sites with high posterior probabilities. Compared these features with shallow sea starfish, we predict that variation specifically in atp8, nad2, and nad5 may play an important role in F. benthophila's adaptation to deep-sea environment.
