A novel fragmented mitochondrial genome in the protist pathogen Toxoplasma gondii and related tissue coccidia
- Sivaranjani Namasivayam1,2,
- Rodrigo P. Baptista2,3,
- Wenyuan Xiao1,2,
- Erica M. Hall1,
- Joseph S. Doggett4,5,
- Karin Troell6 and
- Jessica C. Kissinger1,2,3
- 1Department of Genetics, University of Georgia, Athens, Georgia 30602, USA;
- 2Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia 30602, USA;
- 3Institute of Bioinformatics, University of Georgia, Athens, Georgia 30602, USA;
- 4Division of Infectious Diseases, Oregon Health Sciences University, Portland, Oregon 97239, USA;
- 5Division of Infectious Diseases, Veterans Affairs Portland Health Care System, Portland, Oregon 97239, USA;
- 6Department of Microbiology, National Veterinary Institute, SE-751 89 Uppsala, Sweden
Abstract
Mitochondrial genome content and structure vary widely across the eukaryotic tree of life, with protists displaying extreme examples. Apicomplexan and dinoflagellate protists have evolved highly reduced mitochondrial genome sequences, mtDNA, consisting of only three cytochrome genes and fragmented rRNA genes. Here, we report the independent evolution of fragmented cytochrome genes in Toxoplasma and related tissue coccidia and evolution of a novel genome architecture consisting minimally of 21 sequence blocks (SBs) totaling 5.9 kb that exist as nonrandom concatemers. Single-molecule Nanopore reads consisting entirely of SBs ranging from 0.1 to 23.6 kb reveal both whole and fragmented cytochrome genes. Full-length cytochrome transcripts including a divergent coxIII are detected. The topology of the mitochondrial genome remains an enigma. Analysis of a cob point mutation reveals that homoplasmy of SBs is maintained. Tissue coccidia are important pathogens of man and animals, and the mitochondrion represents an important therapeutic target. The mtDNA sequence has been elucidated, but a definitive genome architecture remains elusive.
Footnotes
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[Supplemental material is available for this article.]
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Article published online before print. Article, supplemental material, and publication date are at https://www.genome.org/cgi/doi/10.1101/gr.266403.120.
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Freely available online through the Genome Research Open Access option.
- Received May 24, 2020.
- Accepted March 9, 2021.
This article, published in Genome Research, is available under a Creative Commons License (Attribution-NonCommercial 4.0 International), as described at http://creativecommons.org/licenses/by-nc/4.0/.
