Peculiarities within peculiarities – dinoflagellates and their mitochondrial genomes

Gagat, Przemysław; Mackiewicz, Dorota; Mackiewicz, Paweł

doi:10.1080/23802359.2017.1307699

Cited by 13 publications

(14 citation statements)

References 42 publications

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“…The SBs are evolutionarily conserved with a few minor variations in Hammondia hammondi and the more divergent N. caninum but not Sarcocystis. We also show that this lineage has independently evolved fragmentation of the coxI, coxIII, and cob genes, a feature previously detected only in dinoflagellates (Flegontov et al 2015;Obornik and Lukes 2015;Gagat et al 2017), perhaps as a mechanism to generate novelty in these streamlined mtDNA genomes.…”

Section: Discussionsupporting

confidence: 61%

A novel fragmented mitochondrial genome in the protist pathogen Toxoplasma gondii and related tissue coccidia

et al. 2021

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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.

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Section: Discussionsupporting

confidence: 61%

A novel fragmented mitochondrial genome in the protist pathogen Toxoplasma gondii and related tissue coccidia

et al. 2021

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“…The loss of the mitochondrion is accompanied by the loss of the plastid remnant and a reduction of the nuclear genome. It is thought that the abundance of host-derived nutrients combined with anaerobic/hypoxic growth conditions support the massive reduction in the mitochondrial metabolic capability in cryptosporidians (Gagat et al, 2017). Two additional independent mitochondrial functional reductions and electron chain losses within Apicomplexa have been recently shown to have occurred amongst gregarines (Mathur et al, 2021;Salomaki et al, 2021).…”

Section: The Mitochondria Of Apicomplexansmentioning

confidence: 99%

“…Dinoflagellates have increased their mitogenome size by accumulating a surprisingly high (99%) percentage of noncoding and repetitive sequence elements, reaching mitogenome sizes of up to 300 kb. It has been proposed that these sequence additions might be functional and positively selected in freeliving organisms subject to more stringent metabolic conditions than those which have remained exclusively parasitic and under a scenery of relaxed selection (Gagat et al, 2017). Comparatively, mitogenomes in Apicomplexa are generally small, with the largest one characterized to date being of less than 30 kb, and the majority being smaller than 12 kb (Figure 1).…”

Section: The Mitochondria Of Apicomplexansmentioning

confidence: 99%

“…Nonetheless, no correlation per se has been established between the mitochondrial genome size and its gene content. This is clearly illustrated by the fact that ciliates, whose mitogenomes encode for tens of proteins usually range from 50 to 70 kb in size while dinoflagellates bear mitochondrial genomes of about 300 kb, but conserve only three protein coding genes (Burger et al, 2003;Gagat et al, 2017;Park et al, 2019). Variations in genome sizes are mostly caused by repetitive elements, and differences in the length and organization of intergenic regions.…”

Section: The Mitochondria Of Apicomplexansmentioning

confidence: 99%

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The Elusive Mitochondrial Genomes of Apicomplexa: Where Are We Now?

2021

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Mitochondria are vital organelles of eukaryotic cells, participating in key metabolic pathways such as cellular respiration, thermogenesis, maintenance of cellular redox potential, calcium homeostasis, cell signaling, and cell death. The phylum Apicomplexa is entirely composed of obligate intracellular parasites, causing a plethora of severe diseases in humans, wild and domestic animals. These pathogens include the causative agents of malaria, cryptosporidiosis, neosporosis, East Coast fever and toxoplasmosis, among others. The mitochondria in Apicomplexa has been put forward as a promising source of undiscovered drug targets, and it has been validated as the target of atovaquone, a drug currently used in the clinic to counter malaria. Apicomplexans present a single tubular mitochondria that varies widely both in structure and in genomic content across the phylum. The organelle is characterized by massive gene migrations to the nucleus, sequence rearrangements and drastic functional reductions in some species. Recent third generation sequencing studies have reignited an interest for elucidating the extensive diversity displayed by the mitochondrial genomes of apicomplexans and their intriguing genomic features. The underlying mechanisms of gene transcription and translation are also ill-understood. In this review, we present the state of the art on mitochondrial genome structure, composition and organization in the apicomplexan phylum revisiting topological and biochemical information gathered through classical techniques. We contextualize this in light of the genomic insight gained by second and, more recently, third generation sequencing technologies. We discuss the mitochondrial genomic and mechanistic features found in evolutionarily related alveolates, and discuss the common and distinct origins of the apicomplexan mitochondria peculiarities.

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“…Much more work is needed before one can definitively say if members of the Amoebophrya genus have or do not have an mtDNA. But, for now, the data are pointing toward the existence of a mitochondrial genome, albeit one that might be among the most reduced of all eukaryotes, even more so than the highly reduced mtDNAs of other myzozoans ( Gagat et al. 2017 ).…”

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confidence: 99%

Is the Dinoflagellate Amoebophrya Really Missing an mtDNA?

Kayal

Smith

2021

Molecular Biology and Evolution

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Mitochondrial DNA (mtDNA) is a universal hallmark of aerobic eukaryotes. That is why the recent suggestion by John et al. (2019) that the aerobic dinoflagellate Amoebophrya sp. strain AT5 (Syndiniales) lacks mtDNA was so remarkable. Here, by reanalysing recently published genomic and transcriptomic data from three Amoebophrya strains, we provide evidence of a cryptic, highly reduced mtDNA in this clade. More work is needed before one can definitively say if Amoebophrya has or does not have a mtDNA, but for now the data are pointing towards the existence of one. Ultimately, we urge caution when basing supposedly absent genomic features on single line evidences.

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Peculiarities within peculiarities – dinoflagellates and their mitochondrial genomes

Cited by 13 publications

References 42 publications

A novel fragmented mitochondrial genome in the protist pathogen Toxoplasma gondii and related tissue coccidia

A novel fragmented mitochondrial genome in the protist pathogen Toxoplasma gondii and related tissue coccidia

The Elusive Mitochondrial Genomes of Apicomplexa: Where Are We Now?

Is the Dinoflagellate Amoebophrya Really Missing an mtDNA?

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