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  • 1
    Electronic Resource
    Electronic Resource
    Concerted evolution in protists: Recent homogenization of a polyubiquitin gene in Trichomonas vaginalis (1995)
    Springer
    Journal of molecular evolution 41 (1995), S. 556-562 
    Details
    ISSN: 1432-1432
    Keywords: Protests ; Trichomonas vaginalis ; Polyubiquitin gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ubiquitin is a 76-amino-acid protein with a remarkably high degree of conservation between all known sequences. Ubiquitin genes are almost always multicopy in eukaryotes, and often are found as polyubiquitin genes—fused tandem repeats which are coexpressed. Seventeen ubiquitin sequences from the amitochondrial protist Trichomonas vaginalis have been examined here, including an 11-repeat fragment of a polyubiquitin gene. These sequences reveal a number of interesting features that are not seen in other eukaryotes. The predicted amino acid sequences lack several universally conserved residues, and individual units do not always encode identical peptides as is usually the case. On the nucleotide level, these repeats are in general highly variable, but one region in the polyubiquitin is extremely homogeneous, with seven repeats absolutely identical. Such extended stretches of homogeneity have never been observed in ubiquitin genes and since substitutions are common in other coding units, it is likely that these repeats are the product of a very recent homogenization or amplification.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00175813
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  • 2
    Electronic Resource
    Electronic Resource
    Evolutionary Relationship Between Translation Initiation Factor eIF-2γ and Selenocysteine-Specific Elongation Factor SELB: Change of Function in Translation Factors (1998)
    Springer
    Journal of molecular evolution 47 (1998), S. 649-655 
    Details
    ISSN: 1432-1432
    Keywords: Key words: Translation initiation — eIF-2 — SELB — EF-Tu — Selenocysteine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Eubacterial and eukaryotic translation initiation systems have very little in common, and therefore the evolutionary events that gave rise to these two disparate systems are difficult to ascertain. One common feature is the presence of initiation, elongation, and release factors belonging to a large GTPase superfamily. One of these initiation factors, the γ subunit of initiation factor 2 (eIF-2γ), is found only in eukaryotes and archaebacteria. We have sequenced eIF-2γ gene fragments from representative diplomonads, parabasalia, and microsporidia and used these new sequences together with new archaebacterial homologues to examine the phylogenetic position of eIF-2γ within the GTPase superfamily. The archaebacterial and eukaryotic eIF-2γ proteins are found to be very closely related, and are in turn related to SELB, the selenocysteine-specific elongation factor from eubacteria. The overall topology of the GTPase tree further suggests that the eIF-2γ/SELB group may represent an ancient subfamily of GTPases that diverged prior to the last common ancestor of extant life.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00006422
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  • 3
    Electronic Resource
    Electronic Resource
    UAR Codons for Glutamine (1997)
    Springer
    Journal of molecular evolution 45 (1997), S. 207-208 
    Details
    ISSN: 1432-1432
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/
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  • 4
    Electronic Resource
    Electronic Resource
    Parasites go the full monty (2001)
    [s.l.] : Nature Publishing Group
    Nature 414 (2001), S. 401-402 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Parasites are well known for stripping themselves down to the bare essentials, but how far will they go? Microsporidia are one group of single-celled parasites that have taken it to extremes and gone the 'full monty'. On page 450 of this issue, Katinka and colleagues expose the shocking ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35106666
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  • 5
    Electronic Resource
    Electronic Resource
    Phylogeny Parabasalian flagellates are ancient eukaryotes (2000)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 405 (2000), S. 635-637 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Discrepancies between eukaryotic phylogenetic trees based on different gene sequences have led to the suggestion that the deepest branches of each gene tree could simply be artefacts of rapid evolution rather than indicators of an ancient divergence. But if an insertion or deletion ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35015167
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  • 6
    Electronic Resource
    Electronic Resource
    MICROSPORIDIA: Biology and Evolution of Highly Reduced Intracellular Parasites (2002)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Microbiology 56 (2002), S. 93-116 
    Details
    ISSN: 0066-4227
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Microsporidia are a large group of microbial eukaryotes composed exclusively of obligate intracellular parasites of other eukaryotes. Almost 150 years of microsporidian research has led to a basic understanding of many aspects of microsporidian biology, especially their unique and highly specialized mode of infection, where the parasite enters its host through a projectile tube that is expelled at high velocity. Molecular biology and genomic studies on microsporidia have also drawn attention to many other unusual features, including a unique core carbon metabolism and genomes in the size range of bacteria. These seemingly simple parasites were once thought to be the most primitive eukaryotes; however, we now know from molecular phylogeny that they are highly specialized fungi. The fungal nature of microsporidia indicates that microsporidia have undergone severe selective reduction permeating every level of their biology: From cell structures to metabolism, and from genomics to gene structure, microsporidia are reduced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.micro.56.012302.160854
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  • 7
    Electronic Resource
    Electronic Resource
    Linked Genes for Calmodulin and E2 Ubiquitin-Conjugating Enzyme in Trichomonas vaginalis (1996)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 43 (1996), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In searching the genomes of early-diverging protists to study whether the possession of calmodulin is ancestral to all eukaryotes, the gene for calmodulin was identified in Trichomonas vaginalis. This flagellate is a member of the Parabasalia, one of the earliest lineages of recognized eukaryotes to have diverged. This sequence was used to isolate a homologous 1.250-kb fragment from the T. vaginalis genome by inverse polymerase chain reaction. This fragment was also completely sequenced and shown to contain the 3′ end of the single-copy calmodulin gene and the 3′ end of a gene encoding a protein with high similarity to E2 ubiquitin-conjugating enzymes, a family which has previously only been identified in animals, plants, and fungi. Phylogenetic analysis of 50 members of the E2 family distinguishes at least nine separate subfamilies one of which includes the T. vaginalis E2-homologue and an uncharacterized gene from yeast chromosome XII.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.1996.tb04506.x
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  • 8
    Electronic Resource
    Electronic Resource
    Plastid-Targeting Peptides from the Chlorarachniophyte Bigelowiella natans (2004)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 51 (2004), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Chlorarachniophytes are marine amoeboflagellate protists that have acquired their plastid (chloroplast) through secondary endosymbiosis with a green alga. Like other algae, most of the proteins necessary for plastid function are encoded in the nuclear genome of the secondary host. These proteins are targeted to the organelle using a bipartite leader sequence consisting of a signal peptide (allowing entry in to the endomembrane system) and a chloroplast transit peptide (for transport across the chloroplast envelope mem branes). We have examined the leader sequences from 45 full-length predicted plastid-targeted proteins from the Chlorarachniophyte Bigelowiella natans with the goal of understanding important features of these sequences and possible conserved motifs. The chemical characteristics of these sequences were compared with a set of 10 B. natans endomembrane-targeted proteins and 38 cytosolic or nuclear proteins, which show that the signal peptides are similar to those of most other eukaryotes, while the transit peptides differ from those of other algae in some characteristics. Consistent with this, the leader sequence from one B. natans protein was tested for function in the apicomplexan parasite, Toxoplasma gondii, and shown to direct the secretion of the protein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.2004.tb00288.x
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  • 9
    Electronic Resource
    Electronic Resource
    Symbiotic Innovation in the Oxymonad Streblomastix strix (2004)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 51 (2004), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: . Streblomastix strix is an enigmatic oxymonad found exclusively in the hindgut of the damp-wood termite Zootermopsis. Streblomastix has a number of unusual morphological characters and forms a complex but poorly understood symbiosis with epibiotic bacteria. Here we described the ultrastructure of S. strix, with emphasis on the axial cytoskeleton and cell-cell associations, in its normal state and when treated with antibiotics. In untreated cells, epibiotic bacteria were orderly arranged end-to-end on six or seven longitudinal vanes, giving S. strix a stellate appearance in transverse section. The epibiotic bacteria were unusually long bacilli of at least three different morphotypes. Bacteria adhered to the oxymonad host by distinct cell-cell junctions that protruded between the poles of adjacent epibiotic bacteria. Treating termites with the antibiotic carbenicillin led to the loss of most (but not all) of the bacteria and the transformation of 5. strix from a long slender cell to a teardrop-shaped cell, where the axostyle was compacted and became bifurcated near the posterior end.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.2004.tb00569.x
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  • 10
    Electronic Resource
    Electronic Resource
    Transfer of Nosema locustae (Microsporidia) to Antonospora locustae n. comb. Based on Molecular and Ultrastructural Data (2004)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 51 (2004), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: . Nosema locustae is a microsporidian parasite of grasshopper pesthd that is used as a biological control agent, and is one of the emerging model systems for microsporidia. Due largely to its diplokaryotic nuclei, N. locustae has been classified in the genus Nosema, a large genus with members that infect a wide variety of insects. However, some molecular studies have cast doubt on the validity of certain Nosema species, and on the taxonomic position of N. locustae. To clarify the affinities of this important insect parasite we sequenced part of the rRNA operon of N. locustae and conducted a phylogenetic analysis using the complete small subunit rRNA gene. Nosema locustae is only distantly related to the nominotypic N. bombycis, and is instead closely related to Antonospora scoticae, a recently described parasite of bees. We examined the ultrastructure of mature N. locustae spores, and found the spore wall to differ from true Nosema species in having a multi-layered exospore resembling that of Antonospora (one of the distinguishing features of that genus). Based on both molecular and morphological evidence, therefore, we propose transferring N. locustae to the genus Antonospora, as Antonospora locustae n. comb.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.2004.tb00547.x
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