RT Journal
A1 Namasivayam, Sivaranjani
A1 Baptista, Rodrigo P.
A1 Xiao, Wenyuan
A1 Hall, Erica M.
A1 Doggett, Joseph S.
A1 Troell, Karin
A1 Kissinger, Jessica C.
T1 A novel fragmented mitochondrial genome in the protist pathogen Toxoplasma gondii and related tissue coccidia
JF Genome Research 
JO Genome Research 
YR 2021 
FD May 01 
VO 31 
IS 5 
SP 852 
OP 865 
DO 10.1101/gr.266403.120 
UL http://genome.cshlp.org/content/31/5/852.abstract 
AB 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.