Arguments based on cell energetics favour the view that a mitochondrion capable of oxidative phosphorylation was a prerequisite for the evolution of other features of the eukaryotic cell, including increased volume, genome size and, eventually, phagotrophy. Contrary to this we argue that: (i) extant amitochondriate eukaryotes possess voluminous phagotrophic cells with large genomes; (ii) picoeukaryotes demonstrate that phagotrophy is feasible at prokaryotic cell sizes; and (iii) the assumption that evolution of complex features requires extra ATP, often mentioned in this context, is unfounded and should not be used in such considerations. We claim that the diversity of cell organisations and functions observed today in eukaryotes gives no reason to postulate that a mitochondrion must have preceded phagocytosis in eukaryogenesis.
- Klíčová slova
- eukaryogenesis, eukaryotic anaerobes, last eukaryotic common ancestor, mitochondrion, phagocytosis,
- MeSH
- adenosintrifosfát MeSH
- Archaea fyziologie MeSH
- biologická evoluce * MeSH
- Eukaryota genetika fyziologie MeSH
- eukaryotické buňky fyziologie MeSH
- fagocytóza MeSH
- genom MeSH
- mitochondrie genetika fyziologie MeSH
- prokaryotické buňky fyziologie MeSH
- symbióza MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- přehledy MeSH
- Názvy látek
- adenosintrifosfát MeSH
Frataxin is a small conserved mitochondrial protein; in humans, mutations affecting frataxin expression or function result in Friedreich's ataxia. Much of the current understanding of frataxin function comes from informative studies with yeast models, but considerable debates remain with regard to the primary functions of this ubiquitous protein. We exploit the tractable reverse genetics of Trypanosoma brucei in order to specifically consider the importance of frataxin in an early branching lineage. Using inducible RNAi, we show that frataxin is essential in T. brucei and that its loss results in reduced activity of the marker Fe-S cluster-containing enzyme aconitase in both the mitochondrion and cytosol. Activities of mitochondrial succinate dehydrogenase and fumarase also decreased, but the concentration of reactive oxygen species increased. Trypanosomes lacking frataxin also exhibited a low mitochondrial membrane potential and reduced oxygen consumption. Crucially, however, iron did not accumulate in frataxin-depleted mitochondria, and as T. brucei frataxin does not form large complexes, it suggests that it plays no role in iron storage. Interestingly, RNAi phenotypes were ameliorated by expression of frataxin homologues from hydrogenosomes of another divergent protist Trichomonas vaginalis. Collectively, the data suggest trypanosome frataxin functions primarily only in Fe-S cluster biogenesis and protection from reactive oxygen species.
- MeSH
- buněčné linie MeSH
- eukaryotické buňky klasifikace fyziologie MeSH
- exprese genu * MeSH
- fenotyp MeSH
- frataxin MeSH
- fylogeneze MeSH
- lidé MeSH
- mitochondriální proteiny chemie genetika metabolismus MeSH
- molekulární evoluce * MeSH
- molekulární sekvence - údaje MeSH
- prokaryotické buňky klasifikace fyziologie MeSH
- proteiny obsahující železo a síru chemie genetika metabolismus MeSH
- proteiny vázající železo chemie genetika metabolismus MeSH
- protozoální proteiny chemie genetika metabolismus MeSH
- RNA interference MeSH
- sekvence aminokyselin MeSH
- sekvenční seřazení MeSH
- Trichomonas chemie klasifikace genetika metabolismus MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- mitochondriální proteiny MeSH
- proteiny obsahující železo a síru MeSH
- proteiny vázající železo MeSH
- protozoální proteiny MeSH
The DicodonUse programme is aimed at a fast and simple assessment of genes present in prokaryotic nucleotide sequences. It identifies open reading frames that are not genes, and it distinguishes the genes that inherently belong to the genome in question from the genes that were inserted into the genome in the course of evolution. The programme is based on frequencies of dicodons used by the organism.
