Study on genetic differentiation ofSchistosome japonicumintermediate hostsOncomelania hupensis robertsoniin hilly regions of China: using the complete mitochondrial genome
Authors: Song Jing , Wang Hongqiong , Li Shizhu , Zhang Zongya , Li Chunying , Zhou Jihua , Shen Meifen , Qian Peijun , Wang Wenya , Zhang Yun , Chen Chunqiong , Wang Lifang , Sun Jiayu , Hao Yuwan , Du Chunhong , Dong Yi 
Published: November 2023

Objective

Oncomelania hupensis robertsoniis the only intermediate host ofSchistosoma japonicumin western China, its genetic differentiation directly impacts the susceptibility ofSchistosoma japonicum.This study aimed to sequence the complete mitochondrial genome ofOncomelania hupensis robertsoniYunnan strain and analyze the genetic differentiation ofOncomelania hupensis robertsoniin hilly regions of China.

Methods

Samples were from 14 administrative villages in Yunnan Province of China, with 30Oncomelania hupensisper village, and the complete mitochondrial genome was sequenced. Additional, we retrieved 14 other regionOncomelania hupensisof complete mitochondrial sequences from GenBank, and a comprehensive analysis of the genetic differentiation ofOncomelania hupensis robertsoniwas conducted by constructing phylogenetic trees, calculating genetic distances, and analyzing homogeneity.

Results

A total of 26 complete mitochondrial sequences were determined. The length of genome ranged from 15,181 to 15,187 bp, and the base composition of the genome was A+T (67.5%) and G+C content (32.5%). This genome encoded 37 genes, including 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes and a non-coding region rich in A+T. Using the Philippines genotypes as outgroup, the phylogenetic trees and homology analysis confirmed the existence of two distinct phylogroups,Oncomelania hupensis robertsoniand the remaining 9 provincial genotypes.Oncomelania hupensis robertsoniis subdivided intoOncomelania hupensis robertsoniYunnan strain and Sichuan strain, with a genetic distance of 0.0834.Oncomelania hupensis robertsoniYunnan strain is subdivided into two subbranches, “Yunnan North” and “Yunnan South”, with a genetic distance of 0.0216, and the samples exhibited over 97% homology.

Conclusion

Oncomelania hupensis robertsoniYunnan strain exhibits a higher level of genetic homology and clear north-south differentiation, the distribution characteristics were closely associated with watershed distribution. This work reported the first mitochondrial genome ofOncomelania hupensis robertsoniYunnan strain, which could be used as an important reference genome forOncomelania hupensis, and also provide a theoretical basis for explaining the distribution pattern ofOncomelania hupensis robertsoniand control of schistosomiasis.

Author Summary

Oncomelania hupensis(O. hupensis) is the only intermediate host ofSchistosoma japonicum(S. japonicum),O. hupensisresiding in different geographical regions display morphological differences and genetic variations, along with varying susceptibility toS. japonicum. In this study, we sequenced 26 complete mitochondrial genome ofO. hupensis robertsoniYunnan strain (O. h. r.Yunnan strain), the length of genome ranged from 15,181 to 15,187 bp, and the base composition of the genome was A+T (67.5%) and G+C content (32.5%). This genome encoded 37 genes, including 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes and a non-coding region rich in A+T. Additional, we retrieved 14 other regionO. hupensisof complete mitochondrial sequences from GenBank. The phylogenetic trees and homology analysis confirmed thatO. hupensis robertsoniis subdivided into Yunnan strain and Sichuan strain, andO. h. r.Yunnan strain is subdivided into two subbranches, “Yunnan North” and “Yunnan South”, the samples exhibited over 97% homology. This work reported the first mitochondrial genome ofO. h. r.Yunnan strain, which could be used as an important reference genome forO. hupensis, and also provide a molecular biology-based theoretical foundation for understanding the genetic differentiation ofO. hupensis.