Next-generation sequencing reveals the mitogenomic heteroplasmy in the topmouth culter (Culter alburnus Basilewsky, 1855)

Background The mitogenomic heteroplasmy is the presence of multiple haplotypes in the mitochondria, which could cause genetic diseases and is also associated with many critical biological functions. The topmouth culter (Culter alburnus Basilewsky, 1855) is one of the most important freshwater fish in the family of Cyprinidae in China. At present, there are no reports on the topmouth culter's mtDNA heteroplasmy and the existence of which is not known. Methods and results This study aimed to analyze the mitogenomic heteroplasmy in the topmouth culter by the next-generation sequencing of the fins' total DNA. The results confirmed the existence of the heteroplasmy and indicated the presence of the extensive heteroplasmy in the topmouth culter's mitogenome. There were 38 heteroplasmic variations in the protein-coding genes from the three specimens, with 33 non-synonymous substitutions accounting for 86.84% and five synonymous substitutions accounting for 13.16%. Among them, the ND6 had the most heteroplasmic variations but only one synonymous substitution. After removing the putative nuclear mitochondrial DNA fragments, the ratio of primary haplotype in the three specimens was 43.89%, 74.72%, and 32.76%, respectively. The three specimens contained 21, 7, and 21 haplotypes of the mitogenomes, respectively. Due to the extensive heteroplasmy, we reconstructed the phylogenetic tree of the topmouth culter using the RY-coding method, which improved the performance of the phylogenetic tree to some extent. Conclusions This study reported the mitogenomic heteroplasmy in the topmouth culter and enhanced the knowledge regarding the mitogenomic heteroplasmy in phylogenetic studies. As the topmouth culter is a commercial species, the mitogenomic heteroplasmy is crucial for the fisheries management of the topmouth culter.

Automated summary

This study confirmed the presence of extensive heteroplasmy in the mitogenome of the topmouth culter, with 38 heteroplasmic variations in the protein-coding genes. The findings enhance the understanding of mitogenomic heteroplasmy in phylogenetic studies and have implications for fisheries management of this commercially important species.