Abstract
The Semicossyphus reticulatus is a marine fish species belongs to the family Labridae. To understand the phylogenetic relationship of S. reticulatus in teleost, we firstly determined the complete mitochondrial genome of S. reticulatus. The entire mitochondrial genome (mtDNA) of S. reticulatus is 16610 bp in length, including 13 protein-coding genes and 2 ribosomal RNA genes, 22 tRNAs and 2 main non-coding regions. The gene arrangement, base composition, and tRNA structures of the mtDNA of S. reticulatus is consistent with those of other teleost. The S. reticulatus mtDNA was used to construct phylogenetic tree, which shows that S. reticulatus is clustered with the fishes of the order Perciformes. We expect that the availability of mtDNA of S. reticulatus will facilitate the further investigations of the taxonomic resolution, biogeography and molecular systematic.
The Labridae is a family of 71 genus and 521 species of marine fishes. As one of the member of the family Labridae, the S. reticulatus is native to Western Pacific: southern Japan, South Korea, and the South China Sea. To research the taxonomic resolution and phylogenetic relationships of S. reticulatus with other vertebrates, we sequenced the complete nucleotide sequence for the mitochondrial genome of S. reticulatus. The samples were collected from the East China Sea (25.75°N, 123.47°E) and was kept at the Museum of Marine Biology at Zhejiang Ocean University (Index number: MMB-2014-0124).
The mitogenome of S. reticulatus is a closed double-stranded circular molecule of 16610 nucleotides (GenBank accession number: KX988261) and contains 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes, the control region (CR) and the origin of the light strand replication (OL). The base composition of S. reticulatus is T 25.1%, C 29.7%, A 27.8%, G 17.5%. The A + T (52.9%) content is higher than G + C (47.2%) content, which is similar to other fishes (Cheng et al. Citation2011; Jin et al. Citation2013). Further more the anti-G bias is ascertained in the third position of protein-coding genes, which brings S. reticulatus in line with other vertebrate mitogenomes (Cheng et al. Citation2012). The two ribosomal RNA genes 12S rRNA and 16S rRNA are located on the heavy strand between tRNAPhe and tRNALeu (UUR), and being separated by tRNAVal gene. The 13 protein-coding genes are encoded on heavy strand except for ND6 which is encoded on the light strand. All the protein-coding genes start ATG, except for COI used GTG as the initiation codon. The stop codon of five protein-coding genes (COI, ATP8, ATP6, ND4L and ND6) is TAA, while ND1 end with TAG and ND5 is AGA. The remaining protein-coding genes (ND2, COII, COIII, ND3, ND4 and Cytb) have incomplete stop codon, either TA or T, which is common to vertebrate mitochondrial protein-coding genes (Xu et al. Citation2011; Cheng et al. Citation2012; Liu et al. Citation2013). And these incomplete termination codons are presumably complete as TAA via posttranscriptional polyadenylation (Ojala et al. Citation1981). The 22 tRNA genes, which contains two forms of tRNASer (UCN and AGY) and tRNALeu (UUR and CUN), scatter throughout the genome and range from 68 to 74 bp in size and the gene arrangement is typically as in most vertebrates. Among the 22 tRNA genes, fourteen are located on the heavy strand and eight on the light strand. Three tRNA clusters (IQM, WANCY, and HSL) are well conserved in S. reticulatus as in other vertebrate mitochondrial genomes (Wei et al. Citation2013). Some overlaps occur in protein-coding genes and tRNAs ranging from 1 to 32 bp, which is similar to most vertebrates. The control region, which is determined to be 1073 bp, located between tRNAPro and tRNAPhe and this characterization is consistent with those of other teleost. Remarkably, the conserved motif 5′-GCCGG-3′, which is involved in the transition from RNA to DNA synthesis, was identified in the mitogenome of S. reticulatus.
Phylogenetic analysis result base on the complete mitochondrial genome sequences demonstrated that S. reticulatus is clustered with the fishes of the order Perciformes (). We expect that this mitogenome sequence data would play a crucial role in phylogenetic analysis of S. reticulatus.
Figure 1. Phylogenetic tree based on the complete mitochondrial genome sequences was constructed using maximum likelihood analyses, all nodes supported with high posterior probabilities (>0.90). The other mitochondrial genome sequences used in phylogenetic analyses were derived from GenBank.
Disclosure statement
No potential conflict of interest was reported by the author(s).
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