Characterization of the complete mitochondrial genome of the tea leaf roller Caloptilia theivora (Insecta: Lepidoptera: Gracillariidae)

Abstract The tea leaf roller, Caloptilia theivora (Walsingham), is a serious pest of tea plants. We have obtained and annotated the complete mitochondrial genome of C. theivora (GenBank accession No. MK541932). The entire mt genome is 15,297 bp long with an A + T content of 80.66%. The mt genome of C. theivora encodes all 37 genes that are typically found in animal mt genomes, consists of 13 protein-coding genes, 2 ribosomal RNA, and 22 transfer RNA genes. The gene order is consistent with other moths mt genome in Ditrysia. The control region of this genome is 192 bp long with a high A + T content of 96.35%, and located between the rrnS and trnI genes. Phylogenetic analysis was performed using 13 protein-coding genes among 19 moths showed that C. theivora is closely related to species of Gracillariidae.

The tea leaf roller, Caloptilia theivora (Walsingham), belonging to the family Gracillariidae in the order Lepidoptera, is a serious pest of tea plants in China and Japan (Kamimuro et al. 2017(Kamimuro et al. , 2018. The larvae feed on the leaves of Camellia sinensis, C. japonica, C. sasanqua, and C. theifera. They sneak the tender leaf or roll the young leaves into triquetrous insect buds for hiding themselves and feeding. The fecal particles accumulated in the insect buds, causing pollution to the leaves and influenceing the tea quality. In this study, we obtained and described the complete mitochondrial genome of Caloptilia theivora for the first time. The larvae of C. theivora were collected from a tea plantation at Yongchuan, Chongqing, China, in 2016, and identified to species by morphology and sequence of cox1 (Nakadai and Kawakita 2016). Voucher specimens (#CQNKY-LE-04-01-01) were deposited at the Insect Collection, Tea Research Institute of Chongqing Academy of Agricultural Science, Chongqing, China.
The complete mt genome of C. theivora is a typical closed-circular and double-stranded DNA molecule in size of 15,297 bp (GenBank accession MK541932). The overall nucleotide composition of the major strand of the tea leaf roller mt genome is as follows: A ¼ 40.99% (6,271), C ¼ 11.43% (1,748), G ¼ 7.92% (1,211) and T ¼ 39.66% (6,067), with a total A þ T content of 80.66%, that is heavily biased toward A and T nucleotides. AT-and GC-skew of the whole J-strand of C. theivora is 0.017 and -0.181, respectively. The mt genome of the tea leaf roller encodes all 37 genes usually found in animal mt genomes, including 13 protein-coding genes, 2 ribosomal RNAs, and 22 transfer RNAs. The control region is 192 bp long and located between the rrnS and trnM genes.
The A þ T content of this region is 96.35%, the highest level of each region in this mt genome. The gene arrangement of this mt genome is conserved as other moths mt genome in Ditrysia. Twenty-three of all 37 genes are encoded on the majority strand (J-strand) and the others encoded by the minority strand (N-strand). Twelve of the 13 PCGs start with ATN codons (ATG for atp6, cox2, nad1, cob, nad4, and nad4L; ATT for atp8, nad2, nad5, and nad6; ATA for cox3 and nad3) and cox1 used CGA as start codon, same situation exists in most Lepidoptera species (Chen et al. 2016). Three PCGs (cox1, cox2, and nad4) have incomplete terminal codons consisting of single T nucleotide, and the other PCGs stop with TAA and TAG. The nucleotide length of tRNA genes is ranging from 61 bp (trnA) to 80 bp (trnS 1 ), and A þ T content is ranging from 70.42% (trnK) to 89.39% (trnD). All of the 22 tRNA genes have the conventional cloverleaf-shaped secondary structure. The two rRNA genes have been identified on the N-strand in the C. theivora mt genome: the rrnL gene locates between trnL 1 and trnV genes, and the rrnS gene between the trnV gene and the control region. The length of rrnL and rrnS genes was 1389 and 770 bp, and their A þ T content was 85.46% and 85.84%, respectively.
We analyzed amino acid sequence of 13 PCGs with the maximum likelihood (ML) method to understand the phylogenetic relationship of C. theivora with other moths. The mt genome sequence of Drosophila melanogaster (GenBank accession no. DMU37541) was used as an outgroup. The tea leaf roller and other three moths in the Family Gracillariidae are clustered into a branch of the phylogenetic tree with 100% bootstrap value (Figure 1). It infers that C. theivora is CONTACT Xiao-Qing Wang wangxiaoqing2891@126.com Tea Research Institute of Chongqing Academy of Agricultural Science, Chongqing 406120, P. R. China closely related to species of Gracillariidae, and the complete mitochondrial genome of C. theivora can be used for further taxonomic analysis.

Disclosure statement
No potential conflict of interest was reported by the authors.