The complete mitochondrial genome of Bombyx lemeepauli (Lepidoptera: Bombycidae) and its phylogenetic relationship

Abstract

The complete mitochondrial genome (mitogenome) of Bombyx lemmepauli Lemée has been sequenced with 15,801 bp in length (Genbank no. KY620270), and has a base composition of A (43.17%), G (7.40%), C (11.90%), and T (37.86%). Similar to other bombyciod species, it contains a typically conserved structure including 13 protein-coding genes (PCGs), 22 transfer RNA genes, 2 ribosomal RNA genes, and an A + T-rich region. Excepting cox1 started with CGA, the start codons of the other 12 PCGs were ATN. Eleven of the 13 PCGs ended with TAA, expect for cox1 and cox2, which ended with a single T. The complete mitogenome sequence provided here would be useful for further understanding the evolutional position of B. lemeepauli, which is a key species to relate the famous resource insect B. mori and the important insect pest Rondotia menciana (Lepidoptera: Bombycidae).

The silkworm moth, Bombyx lemeepauli Lemée (Lepidoptera: Bombycidae) forming a typical white semilunar fasciae on a gray ground color, is endemic to the Himalayan region and is a key species to relate the famous resource insect B. mori and the important insect pest Rondotia menciana (Wang et al. 2015). To ensure and investigate the deeper phylogenetic position, the complete mitochondrial genomes (mitogenome) of B. mori and R. menciana have been determined (Liu et al. 2013; Kong and Yang 2015). However, the B. lemeepauli mitogenome has not been reported.

Here, the mitogenome of B. lemeepauli which adult was collected from Jialing River source scenic spot in Qinling Mountains in China with its genomic DNA stored in Hunan Agricultural University, was sequenced and characterized. Eleven pairs of primer (Gu et al. 2016) were used to amplify the complete mitogenome. The fragments were proof-read by the software Geneious version 8.1.2 (Kearse et al. 2012), and the automatic annotation was performed by the online-program MITOS (http://mitos.bioinf.uni-leipzaig.de) (Bernt et al. 2013) with the annotated genes deposited in GenBank (accession number KY620270). The entire mitogenomes of 25 bombycoid species as ingroups and two geometrid species as outgroups were obtained from NCBI. The conserved regions of the putative amino acids were filtrated by the program Gblock 0.91b with default settings (Castresana 2000). The phylogenetic tree reconstructed by Maximum Likelihood (ML) with 1000 replications and Bayesian Inference (BI) with running for 10,000,000 generations.

The whole mitogenome of B. lemeepauli has a closed circular with 15,801 bp in length, and encoded 37 genes, including 13 PCGs (11,130 bp in total), 22 tRNA genes, 2 rRNA genes, and a putative A + T-rich region. The 209-bp intergenic spacer sequences were observed which the regions dispersed in 17 pairs of neighboring genes with the length varying from 1 to 56 bp. There were 8 overlapping nucleotide fragment in the mitogenome with the longest region between trnL (CUN) and rrnL (−25bp). Excepting cox1 started with CGA, the start codons of the other 12 PCGs were ATN. Regarding the stop codons, eleven PCGs stopped at TAA, except cox1 and cox2. Twenty-two tRNA genes range from 65 to 72 bp in length and display a high AT content of 81.64%. The two rRNA genes, rrnL and rrnS both mapped on the N-strand, were 1392 bp and 791 bp in length.

The evolutionary relationships among the Bombycoidea were reconstructed and the topological structures of the ML and BI trees were identical (Figure 1). The bombycoid was strongly supported as a monophyletic group by the bootstrap value of 100% and the posterior probability of 1.00, and the relationship within this superfamily were Lasiocampidae + (Saturniidae + Endromidae) + (Bombycidae + Sphingidae)). Furthermore, the phylogenetic position of B. lemeepauli among bombycid were T. daii + (R. menciana + (B. lemeepauli + (B. huttoni + (B. mandarina + B. mori) which was supported as a monophyletic clade by a bootstrap value of 100% and a posterior probability of 1.00. The evolutionary relationships of these analyzed species are consistent with previously reported results based on morphological characters (Wang et al. 2015). The newly determined mitogenome will help to understand the evolution of the silk moths.

Figure 1.

Bayesian inference and Maximum likelihood phylogram constructed using 13 PCGs of mitogenomes with partitioned models. Numbers above each node indicates the ML bootstrap support values and the BI posterior probability. All the species’ accession numbers in this study are listed as below: Actias artemis KF927042, Actias selene NC_018133, Andraca theae KX365419, Antheraea frithi NC_027071, Antheraea pernyi NC_004622, Antheraea yamamai NC_012739, Apatelopteryx phenax KJ508055, Attacus atlas NC_021770, Biston panterinaria NC_020004, Bombyx huttoni NC_026518, B. lemeepauli KY620270, Bombyx mandarina NC_003395, Bombyx mori NC_002355, Dendrolimus punctatus NC_027156, Dendrolimus spectabilis NC_025763, Dendrolimus tabulaeformis NC_027157, Eriogyna pyretorum NC_012727, Euthrix laeta NC_031507, Manduca sexta NC_010266, Notonagemia analis KU934302, Phthonandria atrilineata NC_010522, Rondotia menciana NC_021962, Samia canningi NC_024270, Samia cynthia KC812618, Samia ricini NC_017869, Saturnia boisduvalii NC_010613, Sphinx morio NC_020780, Triuncina daii KY091643.

Disclosure statement

The authors have declared that no competing interests exist. The authors alone are responsible for the content of the paper.