Phylogenetic relationship and characterization of the complete mitochondrial genome of Milionia basalis (Lepidoptera: Geometridae).

Larvae of the geometrid moth Milionia basalis feed exclusively on the podocarp tree, Podocarpus macrophyllus. In this study, we sequenced and analyzed the complete mitochondrial genome (mitogenome) of M. basalis. This mitogenome was 15,901 bp long and encoded 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), and two ribosomal RNA unit genes (rRNAs). The whole mitogenome exhibited heavy AT nucleotide bias (82.2%). Gene order was conserved and identical to most other previously sequenced Geometridae. Most PCGs of M. basalis had the conventional start codons ATN, with the exception of nad1 (TTG) and cox1 (CGA). Except for four genes (cox1, cox2, nad5, and nad4) end with the incomplete stop codon T--, all other PCGs terminated with the stop codon TAA. Phylogenetic analysis showed that M. basalis got together with Apocheima cinerarius, Jankowskia athlete, and four Biston species (B. panterinaria, B. perclara, B. suppressaria, and B. thibetaria).

The medium-sized geometrid moth Milionia basalis Druce (Lepidoptera: Geometridae) has orange-banded dark blue wings in the adult stage and is found in some parts of subtropical Asia (Shintani et al. 2018). The larvae of this species feed exclusively on Podocarpus macrophyllus (Podocarpaceae) which is often used as building material or garden tree in some areas (Yasui et al. 2005).

Specimens of M. basalis were collected from Jinggangshan City, Jiangxi Province, China (26°34′N, 114°06′E, July 2019) and were stored in Entomological Museum of Gannan Normal University (Accession number GNU-MB055). After morphological identification, total genomic DNA was extracted from tissues using DNeasy DNA Extraction kit (Qiagen, Hilden, Germany). The mitogenome sequence of M. basalis was generated using Illumina HiSeq 2500 Sequencing System (Illumina, San Diego, CA). In total, 5.2 G raw reads were obtained, quality-trimmed and assembled using MITObim v 1.7 (Hahn et al. 2013). By comparison with the homologous sequences of other Geometridae species from GenBank, the mitogenome of M. basalis was annotated using software GENEIOUS R8 (Biomatters Ltd., Auckland, New Zealand).

The complete mitogenome of M. basalis is 15,901 bp (GenBank accession, MN495623). It contains 13 protein-coding genes (PCGs), 22 tRNA genes, two rRNA genes, and one non-coding AT-rich region. The nucleotide composition of the mitogenome was biased toward A and T, with 82.2% of A + T content (A 41.6%, T 40.6%, C 10.5%, G 7.3%). Gene order was conserved and identical to most other previously sequenced Geometridae (Liu et al. 2014; Chen et al. 2016; Cheng et al. 2017; Sun et al. 2017; Li et al. 2018). Four PCGs (nad4, nad4l, nad5, and nad1) were encoded by the minority strand (N-strand) while the other nine were located on the majority strand (J-strand). Most PCGs of M. basalis had the conventional start codons ATN (five ATG, five ATA, and one ATT), with the exception of nad1 (TTG) and cox1 (CGA). Except for four genes (cox1, cox2, nad5, and nad4) end with the incomplete stop codon T––, all other PCGs terminated with the stop codon TAA. Two rRNA genes (rrnL and rrnS) located at trnL1/trnV and trnV/control region, respectively. The lengths of rrnL and rrnS in M. basalis were 1670 and 789 bp, with the AT contents of 86.9% and 86.6%, respectively. The 22 tRNA genes vary from 65 bp (trnE, trnG, and trnT) to 71 bp (trnK).

Phylogenetic tree was constructed using the maximum-likelihood method through raxmlGUI 1.5 (Silvestro and Michalak 2012) based on 13 mitochondrial protein-coding genes sequences. Results showed that the new sequenced species M. basalis got together with Apocheima cinerarius, Jankowskia athlete and four Biston species (B. panterinaria, B. perclara, B. suppressaria, and B. thibetaria), indicating the close relationship of these four genus (Figure 1). In conclusion, the mitogenome of M. basalis is sequenced in this study and can provide essential DNA molecular data for further phylogenetic and evolutionary analysis of Geometridae.

Figure 1.

Phylogenetic relationships based on the 13 mitochondrial protein-coding genes sequences inferred from RaxML. Numbers on branches are Bootstrap support values (BS).