Mitochondrial Genome Sequences and Structures Aid in the Resolution of Piroplasmida phylogeny.
The taxonomy of the order Piroplasmida, which includes a number of clinically and economically relevant organisms, is a hotly debated topic amongst parasitologists. Three genera (Babesia, Theileria, and Cytauxzoon) are recognized based on parasite life cycle characteristics, but molecular phylogenetic analyses of 18S sequences have suggested the presence of five or more distinct Piroplasmida lineages. Despite these important advancements, a few studies have been unable to define the taxonomic relationships of some organisms (e.g. C. felis and T. equi) with respect to other Piroplasmida. Additional evidence from mitochondrial genome sequences and synteny should aid in the inference of Piroplasmida phylogeny and resolution of taxonomic uncertainties. In this study, we have amplified, sequenced, and annotated seven previously uncharacterized mitochondrial genomes (Babesia canis, Babesia vogeli, Babesia rossi, Babesia sp. Coco, Babesia conradae, Babesia microti-like sp., and Cytauxzoon felis) and identified additional ribosomal fragments in ten previously characterized mitochondrial genomes. Phylogenetic analysis of concatenated mitochondrial and 18S sequences as well as cox1 amino acid sequence identified five distinct Piroplasmida groups, each of which possesses a unique mitochondrial genome structure. Specifically, our results confirm the existence of four previously identified clades (B. microti group, Babesia sensu stricto, Theileria equi, and a Babesia sensu latu group that includes B. conradae) while supporting the integration of Theileria and Cytauxzoon species into a single fifth taxon. Although known biological characteristics of Piroplasmida corroborate the proposed phylogeny, more investigation into parasite life cycles is warranted to further understand the evolution of the Piroplasmida. Our results provide an evolutionary framework for comparative biology of these important animal and human pathogens and help focus renewed efforts toward understanding the phylogenetic relationships within the group.
North Carolina State University, College of Veterinary Medicine, Raleigh, North Carolina, United States of America.
Megan E
http://orcid.org/0000-0001-5649-8854
ME
Schreeg
North Carolina State University, College of Veterinary Medicine, Raleigh, North Carolina, United States of America.
Henry S
HS
Marr
North Carolina State University, College of Veterinary Medicine, Raleigh, North Carolina, United States of America.|University of Georgia, College of Veterinary Medicine, Athens, Georgia, United States of America.
Jaime L
JL
Tarigo
University of Missouri, College of Veterinary Medicine, Columbia, Missouri, United States of America.
Leah A
LA
Cohn
North Carolina State University, College of Agriculture and Life Sciences, Raleigh, North Carolina, United States of America.
David M
DM
Bird
North Carolina State University, College of Agriculture and Life Sciences, Raleigh, North Carolina, United States of America.
Elizabeth H
EH
Scholl
North Carolina State University, College of Veterinary Medicine, Raleigh, North Carolina, United States of America.
Michael G
MG
Levy
North Carolina State University, College of Agriculture and Life Sciences, Raleigh, North Carolina, United States of America.
Brian M
BM
Wiegmann
North Carolina State University, College of Veterinary Medicine, Raleigh, North Carolina, United States of America.
Adam J
AJ
Birkenheuer
D016054:DNA, Protozoan / Q000235:genetics; D054629:Genome, Mitochondrial; D006801:Humans; D010802:Phylogeny; D016792:Piroplasmida / Q000145:classification / Q000235:genetics*; D011528:Protozoan Infections / Q000469:parasitology
D016054:DNA, Protozoan