The complete mitochondrial genome of the wild silkmoth Antheraea yamamai from Heilongjiang, China (Lepidoptera: Saturniidae).

Here, we reported the complete mitochondrial genome of Antheraea yamamai Guérin-Méneville (1861) collected in Heilongjiang Province, China. The mitochondrial genome is 15,341 bp and encodes 13 protein-coding genes, two ribosomal RNA genes, and 22 transfer RNA genes. Sequence comparison identified 22 SNVs in the A. yamamai mitochondrial genomes between Chinese and Korean populations, indicating a low intraspecific variation between the two populations . Phylogenetic analyses with maximum-likelihood and Bayesian inference methods revealed a close relationship between A. yamamai and Antheraea frithi and supported the relationship among Antheraea species (((A. yamamai + A. frithi) + A. pernyi) + A. assamensis).

The wild silkmoth Antheraea yamamai Guérin-Méneville (1861) is one of the most well-known wild silkmoths belonging to the family Saturniidae. This species is distributed throughout China, Korea, Japan, and Russia. Antheraea yamamai produces green silk called Tensan silk, which has been considered a new biomaterial and a useful product in human health research and economic fields (Kim et al. 2018). The pupae of this species are also considered to be potential insect-derived food resources with high nutritional value (Yue et al. 2017). To date, this insect is still a noncultivated silkmoth reared outdoors. To protect this economically important silkmoth resource as well as its living environment, the province-level Shuguang Nature Reserve (N45°47′40′′ ∼ 45°35′27′′; E131°03′20′′ ∼ 131°11′17′′) was created in Heilongjiang Province, China (Hou et al. 2010). In the present study, we reported the complete mitochondrial genome of this wild silkmoth collected in the Shuguang Nature Reserve to provide basic genetic information.

The A. yamamai eggs collected in the Shuguang Nature Reserve were kindly provided by Tian-Mao Wang, Developmental Center of Heilongjiang Provincial Sericulture and Bee Industry (N45°54′; E126°39′), Harbin, China. After hatching, the larvae were fed with the leaves of Salix viminalis in the Silkmoth Experimental Field of Shenyang Agricultural University (N41°50′1.08′′; E123°34′21.92′′). An adult specimen was deposited at the Department of Sericulture, Shenyang Agricultural University, China (https://www.syau.edu.cn/, Dr. Yan-Qun Liu, liuyanqun@syau.edu.cn) under voucher number SILKMOTH_YAMAMAI_01. A hind leg was used to extract the total genomic DNA, which was also deposited at the Department of Sericulture. Long PCR amplification was used to obtain the whole mitochondrial genome with two species-specific primer pairs. After purification by gel extraction, the amplification products were mixed equally with a sample from Antheraea pernyi Qing_6 and then sequenced on the Illumina PE 150 platform. The resulting clean reads were subjected to the Galaxy web server at usegalaxy.org (https://usegalaxy.eu/) to assemble the mitochondrial genome (Jalili et al. 2020).

The whole mitochondrial genome of A. yamamai presented here is 15,341 bp in length, thus exhibiting a highly similar size as the reference genome from the Korean population (15,338 bp; EU264055; Kim et al. 2009). This genome also encodes 37 mitochondrial genes, including 13 protein-coding genes, 2 ribosomal RNA genes, and 22 transfer RNA genes, showing an identical genomic component and gene order with known Saturniidae species. The length of the A + T-rich region for A. yamamai is 334 bp, which is similar to those of Antheraea assamensis and Antheraea frithi (328 ∼ 334 bp) but much shorter than that of A. pernyi (516 ∼ 552 bp). Further analysis revealed that the presence of a 38 bp tandem repeat unit (Arunkumar et al. 2006) in A. pernyi resulted in the size variation of the A + T-rich region mentioned above, thus contributing to the length variation of whole mitochondrial genomes of the genus Antheraea.

By sequence comparison, we identified 22 SNVs (19 SNPs and three indels) between the two A. yamamai mitochondrial genomes. Three single-base deletion mutations occurred in the intergenic spacer region ND4-ND4L. Among these 19 SNPs, four were present in rRNAs and one was in the intergenic spacer region ND2-tRNA; the remaining 14 occurred in protein-coding genes, resulting in five amino acid changes. The number of SNVs between the two A. yamamai mitochondrial genomes were smaller than those between the cultivated and noncultivated A. pernyi mitochondrial genomes [264 SNVs (213 SNPs and 51 indels)] and between the two A. assamensis mitochondrial genomes [246 SNVs (158 SNPs and 88 indels)], but similar to those between strains of A. pernyi (Li et al. 2021). These results indicated a low intraspecific variation between Chinese and Korean populations of A. yamamai, suggesting that they might be derived from a common population.

For phylogenetic analysis (Figure 1), seven whole mitochondrial genomes from Antheraea species were included (Kim et al. 2009; Shantibala et al. 2017; Singh et al. 2017; Zhong et al. 2017). Six mitochondrial genomes from non-Antheraea species were also included. Bombyx mori (Lu et al. 2002) served as an outgroup. A maximum-likelihood tree was constructed with IQ-TREE 1.6.12 (Nguyen et al. 2015), and a Bayesian inference tree was constructed with Mrbayes v.3.2 (Ronquist et al. 2012). Our phylogenetic analyses revealed a close relationship between A. yamamai and A. frithi and supported the relationship of the genus Antheraea (((A. yamamai + A. frithi) + A. pernyi) + A. assamensis).

Figure 1.

Phylogenetic tree inferred from the whole mitochondrial genome sequence using the maximum-likelihood method and Bayesian inference method with the GTR + F+R3 model. The numbers at each node are Bayesian posterior probabilities (first value) and bootstrap percentages of 1000 replicates (second value). GenBank accession numbers are listed following the scientific name.