The mitochondrial genome of one ‘twisted-wing parasite’ Xenos cf. moutoni (Insecta, Strepsiptera, Xenidae) from Gaoligong Mountains, Southwest of China

Abstract The nearly complete mitochondrial genome (mitogenome) of Xenos cf. moutoni, one twisted-wing parasite on wasp Vespa velutina from Southwest of China, is described in this study. The total length of this mitogenome is 16,717 bp, containing 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), two ribosomal RNA genes (rRNAs) and an incomplete A + T-rich control region . All of the 13 PCGs are initiated with canonical ATN (N represents A, T, G, C) as start codons; 8 PCGs are terminated with a complete typical stop codon TAA, and the remaining five PCGs (cox2, cox3, nad3, nad4 and nad5) have an incomplete stop codon with just a T. The phylogenetic analysis based on the nucleotide sequences of PCGs and rRNAs indicates that Xenos cf. moutoni has a close relationship with Xenos vesparum, confirming its placement in the family Xenidae.

Both assembled methods (MitoZ and NOVOPlasty) produced the same sequence except A þ T-rich region which is longer in NOVOPlasty assembly than in MitoZ assembly. The mitogenome of Xenos cf. moutoni (GenBank accession No. MW222190) using NOVOPlasty was 16,717 bp in length and 1,658,750 reads were mapped to the mitogenome with 6,904 mean coverage. The linear mitogenome was considered to be incomplete because its two terminuses lack repetitive overlaps with longer than 25 bp (Tang et al. 2014). It contained 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), two ribosomal RNA genes (rRNAs) and an incomplete control (A þ T-rich) region (about 2107 bp). All 13 PCGs are 10,676 bp in length which contain 35.59% A, 9.49% G, 44.30% T and 10.62% C with a strong bias toward A þ T (79.89%). All of 13 PCGs use 'ATN' (N represents A, T, G, C) as the start codons; eight of them are terminated with typical stop codon 'TAA', and the other five (cox2, cox3, nad3, nad4 and nad5) have an incomplete stop codon 'T--'. The length of 22 tRNAs ranges from 56 bp to 69 bp and the size of small rRNA (s-rRNA) and large rRNA (l-rRNA) is 735 bp and 1234 bp, respectively. The arrangement of all 13 PCGs in Xenos cf. moutoni is consistent with those of two other strepsipterans (M. australiensis and X. vesparum) and the luminous beetle R. lufengensis (Carapelli et al. 2006;Li et al. 2007;McMahon et al. 2009). However, some tRNA gene order changes are observed among the four species in those regions between nad3 and nad5, nad5 and nad4 as well as s-rRNA and nad2 and in the location of the trnL1 (Carapelli et al. 2006;Li et al. 2007;McMahon et al. 2009).
Phylogenetic interference was performed among Xenos cf. moutoni and other three reported strepsiperan species (Carapelli et al. 2006;McMahon et al. 2009;Niehuis et al. 2012) with Tribolium castaneum (Coleopetera, Tenebrionidae) as an outgroup. The 13 PCGs and two rRNAs from these species were aligned and concatenated using MEGA-X (Kumar et al. 2018) and then trimmed the unreliably regions using trimAl v1.4 (gt ¼ 0.5) (Capella-Gutierrez and Silla-Martinez 2009). The phylogenetic tree was constructed based on the concatenated nucleotide sequence using RAxML v8.2.10 (Stamatakis 2014) with the GTR þ G þ I model. Our result indicates that Xenos cf. moutoni has a close relationship with X. vesparum in the family Xenidae with high bootstrap values (Figure 1), confirming its placement in the family Xenidae.

Disclosure statement
No potential conflict of interest was reported by the author(s).

Funding
This work was funded by grant from Chinese Academy of Sciences (CAS) 'Light of West China' to LXY.

Data availability statement
The genome sequence data that support the findings of this study are openly available in GenBank of NCBI at https://www.ncbi.nlm.nih.gov, under the accession no. MW222190. The associated BioProject, Bio-Sample and SRA numbers are PRJNA681068, SAMN16898475 and SRR13154212, respectively. Figure 1. The phylogenetic tree of four strepsipteran species based on the nucleotide sequence of concatenated 13 protein-coding genes (PCGs) and two ribosomal RNA genes (rRNAs) using maximum likelihood (ML) analysis. Red flour beetle Tribolium castaneum was selected as the outgroup. The values at the nodes show the bootstrap support calculated using the maximum likelihood method with 100 replicates.