Mitogenomics of the zoonotic parasite Echinostoma miyagawai and insights into the evolution of tandem repeat regions within the mitochondrial non-coding control region.

Abstract

Echinostoma miyagawai is a cosmopolitan parasite within the Echinostomatidae and is a cause of human echinostomiasis. Species within the family have been a challenge to disentangle with E. miyagawai being synonyms of several other Echinostoma species. However, complete mitochondrial genomes have been shown to be vital in distinguishing echinostomatid species, but detailed comparisons of not only gene content but also structural features have been limited. Using long range sequencing techniques, the complete mitochondrial genome of E. miyagawai was sequenced and compared to other members of Echinostomatidae. In total 12 protein coding genes, 2 ribosomal RNA genes and 22 transfer RNA genes were identified, as was an extensive noncoding control region (CR), consisting of 2 types of multiple tandem repeat units. Phylogenetic analyses of complete mitochondrial genomes corresponded to previous studies on single mitochondrial genes and nuclear ribosomal nuclear markers confirmed E. miyagawai to be within in the ‘Echinostoma revolutum’ group. The tandem repeat units found in the CR contained promoter sequences containing domains typical of initiation sites for replication and transcription as well as several palindromic regions which were shared between echinostomatid species. The study illustrates not only the utility complete mitogenomes in disentangling the relationship between these parasite species, but also provides some insight into the potential adaptations and other evolutionary processes that may govern the divergence of mitochondrial genomes for the first time in echinostomatids.