Preaxostyla
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The notion that mitochondria cannot be lost was shattered with the report of an oxymonad Monocercomonoides exilis, the first eukaryote arguably without any mitochondrion. Yet, questions remain about whether this extends beyond the single species and how this transition took place. The Oxymonadida is a group of gut endobionts taxonomically housed in the Preaxostyla which also contains free-living flagellates of the genera Trimastix and Paratrimastix. The latter two taxa harbour conspicuous mitochondrion-related organelles (MROs). Here we report high-quality genome and transcriptome assemblies of two Preaxostyla representatives, the free-living Paratrimastix pyriformis and the oxymonad Blattamonas nauphoetae. We performed thorough comparisons among all available genomic and transcriptomic data of Preaxostyla to further decipher the evolutionary changes towards amitochondriality, endobiosis, and unstacked Golgi. Our results provide insights into the metabolic and endomembrane evolution, but most strikingly the data confirm the complete loss of mitochondria for all three oxymonad species investigated (M. exilis, B. nauphoetae, and Streblomastix strix), suggesting the amitochondriate status is common to a large part if not the whole group of Oxymonadida. This observation moves this unique loss to 100 MYA when oxymonad lineage diversified.
- MeSH
- Eukaryota * genetika MeSH
- fylogeneze MeSH
- genomika MeSH
- mitochondrie genetika MeSH
- Oxymonadida * genetika metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
Trimastigids are free-living, anaerobic protists that are closely related to the symbiotic oxymonads, forming together the taxon Preaxostyla (Excavata: Metamonada). We isolated fourteen new strains morphologically corresponding to two species assigned to Trimastix (until now the only genus of trimastigids), Trimastix marina and Trimastix pyriformis. Unexpectedly, marine strains of Trimastix marina branch separately from freshwater strains of this morphospecies in SSU rRNA gene trees, and instead form the sister group of all other Preaxostyla. This position is confirmed by three-gene phylogenies. Ultrastructural examination of a marine isolate of Trimastix marina demonstrates a combination of trimastigid-like features (e.g. preaxostyle-like I fibre) and ancestral characters (e.g. absence of thickened flagellar vane margins), consistent with inclusion of marine T. marina within Preaxostyla, but also supporting its distinctiveness from 'freshwater T. marina' and its deep-branching position within Preaxostyla. Since these results indicate paraphyly of Trimastix as currently understood, we transfer the other better-studied trimastigids to Paratrimastix n. gen. and Paratrimastigidae n. fam. The freshwater form previously identified as T. marina is described as Paratrimastix eleionoma n. sp., and Trimastix pyriformis becomes Paratrimastix pyriformis n. comb. Because of its phylogenetic position, 'true' Trimastix is potentially important for understanding the evolution of mitochondrion-related organelles in metamonads.
- MeSH
- druhová specificita MeSH
- Eukaryota klasifikace genetika izolace a purifikace ultrastruktura MeSH
- flagella ultrastruktura MeSH
- fylogeneze * MeSH
- organely ultrastruktura MeSH
- RNA ribozomální 18S genetika MeSH
- vodní organismy klasifikace genetika izolace a purifikace ultrastruktura MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The oxymonad Monocercomonoides exilis was recently reported to be the first eukaryote that has completely lost the mitochondrial compartment. It was proposed that an important prerequisite for such a radical evolutionary step was the acquisition of the SUF Fe-S cluster assembly pathway from prokaryotes, making the mitochondrial ISC pathway dispensable. We have investigated genomic and transcriptomic data from six oxymonad species and their relatives, composing the group Preaxostyla (Metamonada, Excavata), for the presence and absence of enzymes involved in Fe-S cluster biosynthesis. None possesses enzymes of mitochondrial ISC pathway and all apparently possess the SUF pathway, composed of SufB, C, D, S, and U proteins, altogether suggesting that the transition from ISC to SUF preceded their last common ancestor. Interestingly, we observed that SufDSU were fused in all three oxymonad genomes, and in the genome of Paratrimastix pyriformis. The donor of the SUF genes is not clear from phylogenetic analyses, but the enzyme composition of the pathway and the presence of SufDSU fusion suggests Firmicutes, Thermotogae, Spirochaetes, Proteobacteria, or Chloroflexi as donors. The inventory of the downstream CIA pathway enzymes is consistent with that of closely related species that retain ISC, indicating that the switch from ISC to SUF did not markedly affect the downstream process of maturation of cytosolic and nuclear Fe-S proteins.
... Třída Retortamonadea 64 -- 2.2.1.2 Třída Trepomonadea 64 -- 2.2.2 Kmen Parabasala 67 -- 2.2.3 Kmen Preaxostyla ...
Vyd. 1. 318 s. : il., tab. ; 24 cm
Parazitismus patří k nejčastějším životním strategiím živých organismů. V popředí našeho zájmu stojí především paraziti napadající člověka a domácí či hospodářská zvířata. Mezi parazity patří i řada přenašečů infekčních chorob. Ačkoli by se zdálo, že nebezpečí těchto infekcí hrozí zejména v tropech a subtropech, setkáváme se s nimi často i v mírném klimatickém pásmu. Díky novým, zejména molekulárně biologickým technikám je parazitologie moderním a bouřlivě se rozvíjejícím oborem. Nová učebnice základů tohoto oboru je zaměřena především na biologii parazitů (např. morfologii, anatomii, fyziologii, životní cykly, interakce parazita s hostitelem), s nezbytnými základními informacemi o průběhu parazitárních onemocnění, epidemiologii a léčbě.
- MeSH
- paraziti MeSH
- parazitologie MeSH
- Publikační typ
- monografie MeSH
- Konspekt
- Buněčná biologie. Cytologie
- NLK Obory
- parazitologie
- biologie
