CHINESE JOURNAL OF PARASITOLOGY AND PARASITIC DISEASES ›› 2023, Vol. 41 ›› Issue (6): 699-707.doi: 10.12140/j.issn.1000-7423.2023.06.006

• ORIGINAL ARTICLES • Previous Articles     Next Articles

Characterization of the mitochondrial genome and phylogenetic implication of Schistosoma japonicum featured with “nocturnal cercarial emergence”

WANG Ning(), PENG Hanqi, GAO Changzhe, CHENG Yuheng, LYU Dabing*()   

  1. Department of Epidemiology and Health Statistics, School of Public Health, Soochow University,Suzhou 215127, Jiangsu, China
  • Received:2023-07-14 Revised:2023-09-12 Online:2023-12-30 Published:2023-12-22
  • Contact: * E-mail: ludabing@suda.edu.cn
  • Supported by:
    National Natural Science Foundation of China(81971957)

Abstract:

Objective This study aimed to determine the complete mitochondrial genome sequence of Schistosoma japonicum featured with nocturnal cercarial emergence pattern and to explore its phylogenetic relationship with other S. japonicum geographical isolates from mainland China, providing new reference data for further study on population genetic structure and genetic diversity. Methods Field Oncomelania hupensis snails were collected from Shitai County of Anhui in 2020, and the infected snails were separated in the laboratory. ICR mice were infected with cercariae shed from the infected snails using abdominal patch method. The worms were obtained by perfusion from hepatic portal and mesenteric vein and randomly sampled for sequencing. The worm genomic DNA was extracted with blood/tissue DNA extraction Kit, and sequenced at paied-end using Illumina NovaSeq 6000 sequencing platform. The mitochondrial genome was assembled using GetOrganelle tool, and its structural features and base composition were analyzed using MEGA 11 software. The phylogenetic tree was constructed using the neighbour-joining (NJ) and maximum likelihood (ML) method based on 17 published mitochondrial genome sequences of S. japonicum from other parts of China. Results The complete circular mitochondrial genome of S. japonicum with nocturnal cercarial emergence pattern isolated from Shitai County of Anhui was 14 085 bp in length(Genbank accession no. ON637109), encoding 36 genes, consisting of 12 protein-coding genes (PCGs), two ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes, with the AT content of 71.35%. There were two gene-overlapping regions and 29 intergenic regions in the mitochondrial genome. Among the 22 tRNA genes, except for trnaC and trnaS1 genes, which missed the dihydrouridine (DHU) arm, the rest were able to form a typical cloverleaf secondary structure. Among the PCGs, the stop codon of cytb, nad4, nad2 and nad6 was TAA, which differed from other geographical strains in China with TAG as the stop codon. Phylogenetic trees constructed based on NJ and ML had similar topologies. The isolated strain of S. japonicum featured with “nocturnal cercarial emergence” in Shitai County, forms a single strain. S. japonicum strains from Taiwan, China and other regions of Chinese Mainland are separated to form one branch. Conclusion The stop codons of S. japonicum isolate from Shitai area of Anhui Province differed from those of other geographical isolates in China. Additionally, based on the phylogenetic analysis, the isolate featured with nocturnal cercarial emergence exhibited a more distant relationship with other regional isolates, showing greater

Key words: Mitochondrial genome, Sequence analysis, Phylogenetic relationship, Schistosoma japonicum, Nocturnal cercarial emergence

CLC Number: