Study on genetic differentiation of Schistosome japonicum intermediate hosts Oncomelania hupensis robertsoni in hilly regions of China: using the complete mitochondrial genome

ObjectiveOncomelania hupensis robertsoni is the only intermediate host of Schistosoma japonicum in western China, its genetic differentiation directly impacts the susceptibility of Schistosoma japonicum. This study aimed to sequence the complete mitochondrial genome of Oncomelania hupensis robertsoni Yunnan strain and analyze the genetic differentiation of Oncomelania hupensis robertsoni in hilly regions of China. MethodsSamples were from 14 administrative villages in Yunnan Province of China, with 30 Oncomelania hupensis per village, and the complete mitochondrial genome was sequenced. Additional, we retrieved 14 other region Oncomelania hupensis of complete mitochondrial sequences from GenBank, and a comprehensive analysis of the genetic differentiation of Oncomelania hupensis robertsoni was conducted by constructing phylogenetic trees, calculating genetic distances, and analyzing homogeneity. ResultsA 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 robertsoni and the remaining 9 provincial genotypes. Oncomelania hupensis robertsoni is subdivided into Oncomelania hupensis robertsoni Yunnan strain and Sichuan strain, with a genetic distance of 0.0834. Oncomelania hupensis robertsoni Yunnan 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. ConclusionOncomelania hupensis robertsoni Yunnan 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 of Oncomelania hupensis robertsoni Yunnan strain, which could be used as an important reference genome for Oncomelania hupensis, and also provide a theoretical basis for explaining the distribution pattern of Oncomelania hupensis robertsoni and control of schistosomiasis. Author SummaryOncomelania hupensis (O. hupensis) is the only intermediate host of Schistosoma japonicum (S. japonicum), O. hupensis residing in different geographical regions display morphological differences and genetic variations, along with varying susceptibility to S. japonicum. In this study, we sequenced 26 complete mitochondrial genome of O. hupensis robertsoni Yunnan 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 region O. hupensis of complete mitochondrial sequences from GenBank. The phylogenetic trees and homology analysis confirmed that O. hupensis robertsoni is subdivided into Yunnan strain and Sichuan strain, and O. 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 of O. h. r. Yunnan strain, which could be used as an important reference genome for O. hupensis, and also provide a molecular biology-based theoretical foundation for understanding the genetic differentiation of O. hupensis.