Abstract
The complete mitochondrial genome of an orb-weaver spider Araneus angulatus is 14,205 bp in length and contains 13 protein-coding genes, 2 ribosomal RNAs, 22 transfer RNAs, and a control region. The A + T content of the major strand is 75.4%. Nine of the protein-coding genes are initiated by typical ATN codons, one gene (COI) starts with TTA and other three genes (ND6, COII, and COIII) begin with TTG. The truncated stop codon (T) occurs in ND3, ND4L, and ND6, whereas the rest ten genes end with the canonical stop codon (TAA and TAG). Fifteen tRNAs lack the potential to form the typically cloverleaf-shaped secondary structure. The control region is 649 bp in length and contains a long tandem repeat region. The result of phylogenetic analysis shows that the relationship of A. angulatus was close to the species in the same family Araneidae.
Keywords: Mitochondrial genome, Araneus angulatus, Araneidae
Mitochondrial genomes are widely used for phylogenetic and phylogeographic analyses among arthropods (Cameron 2014). Spiders are a highly diverse group of arachnids, but there is a lack of sufficient mitochondrial genome sequence data for these taxa to date. Towards a better understanding of the mitogenomic evolution and phylogenetic relationships among Araneae, we sequenced and characterized the complete mitochondrial genome of an orb-weaver spider Araneus angulatus.
The specimen of A. angulatus was collected from a grapery in Tongxiang county (E120°57′, N30°64′), Zhejiang Province, China and deposited in the insect specimen room of China Jiliang University, Hangzhou, China, with an accession number CJLU-TX-2019015. Total genomic DNA was extracted from leg tissue of a single individual using the DNeasy Tissue Kit (Qiagen, Hilden, Germany). The complete mitochondrial genome sequence was amplified by over-lapping extension PCR and annotated via MITOS web server, according to the method described previously (Wang et al. 2016). Maximum likelihood (ML) and Bayesian inference (BI) were both used to reconstruct a mitogenomic phylogeny of Araneae (Huelsenbeck and Ronquist 2001; Guindon and Gascuel 2003). A total of 30 spider mitochondrial genomes available in GenBank were included in our phylogenetic analysis, with the horseshoe crab Limulus polyphemus (Xiphosura) used as an outgroup (Lavrov et al. 2000).
The complete genome sequence of A. angulatus (KU365988) is 14,205 bp in length, which contains 13 protein-coding genes (PCGs), 2 ribosomal RNAs (12S rRNA and 16S rRNA), 22 transfer RNAs (tRNAs) and a control region (CR). The A + T content of the major strand is 75.4% (A: 35.4%; T: 40.0%; G: 15.5%; C: 9.4%). The arrangement of the 13 PCGs shares a similar pattern as those of in other araneids. Only four PCGs (ND5, ND4, ND4L, and ND1) are coded on the minor strand, while the rest are all coded on the major strand. Nine PCGs are initiated by typical ATN codons, one gene (COI) starts with TTA and other three PCGs (ND6, COII, and COIII) begin with TTG. The truncated stop codon (T) occurs in ND3, ND4L, and ND6, whereas the other ten genes end with the canonical stop codon (TAA and TAG). Among 22 tRNAs, only seven of them (tRNACys, tRNAGln, tRNAGly, tRNAIle, tRNALeu(CUN), tRNAPro, and tRNATyr) have the typically cloverleaf-shaped secondary structure. Three tRNAs (tRNASer(AGN), tRNASer(UCN), and tRNAAla) appear to be truncated and lack the potential to form the DHU arm, while the rest twelve tRNAs lack the TψC arm but simplified down to a loop. The control region is 649 bp in length with the A + T content of 71.3% and contains a long tandem repeat region. Phylogenetic analysis based on the 13 protein-coding gene sequences consistently yields trees that nest A. angulatus within Araneidae and recover superfamily Araneoidea as a monophyletic group (Figure 1). Our study will provide fundamental data for further research on mitogenomic evolution and genetic diversities in spiders.
Figure 1.
Phylogenetic reconstruction of 30 spider species based on nucleotide sequences of mitochondrial 13 protein-coding genes using Maximum likelihood (ML) and Bayesian inference (BI). Numbers at the branch indicate the percentages from ML bootstrapping (left) and Bayesian posterior probabilities (right). Spider determined in this study is underlined.
Disclosure statement
No potential conflict of interest was reported by the authors.
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