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  • 11
    Electronic Resource
    Electronic Resource
    Molecular evidence for a single common origin of chromalveolate plastids (2005)
    Oxford, UK : Blackwell Science Inc
    The @journal of eukaryotic microbiology 52 (2005), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Plastids (photosynthetic organelles of plants and algae) are known to have spread between eukaryotic lineages by secondary endosymbiosis, or the uptake of a eukaryotic alga by another eukaryote, but the number of times this has taken place is controversial. This is particularly so in the case of eukaryotes with plastids derived from red algae, which are numerous and diverse. Despite their diversity, it has been suggested that all these eukaryotes share a recent common ancestor and that their plastids originated in a single endosymbiosis, the so-called “chromalveolate hypothesis”. Here, we describe a novel molecular character that supports the chromalveolate hypothesis. Fructose-1,6-bisphosphate aldolase (FBA) is a glycolytic/Calvin cycle enzyme that exists as one of two non-homologous types, class I and class II. Red algal plastid-targeted FBA is a class I enzyme related to homologues from plants and green algae, and it would be predicted that the plastid-targeted FBA from algae with red algal secondary endosymbionts should be related to this class I enzyme. However, we show that heterokonts, cryptomonads, haptophytes and dinoflagellates (all photosynthetic chromalveolates) encode two paralogous class II enzymes, one of which strongly supports a specific relationship between chromalveolates. Exactly where chromalveolates got their plastid-targeted FBA genes is presently uncertain, but their common possession of this unexpected plastid characteristic is compelling evidence for their close relationship and a common origin for their plastids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.2005.05202003_1_40.x
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  • 12
    Electronic Resource
    Electronic Resource
    HSP90, Tubulin and Actin are Retained in the Tertiary Endosymbiont Genome of Kryptoperidinium foliaceum (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: The dinoflagellate Kryptoperidinium foliaceum has replaced its ancestral peridinin-containing plastid with a tucoxanthin-containing diatom plastid via tertiary endosymbiosis. The diatom endosymbiont of K. foliaceum is much less reduced than well-studied endosymbiotic intermediates, such as cryptophytes and chlorarachniophytes, where relict nuclear genomes are retained in secondary endosymbionts. The K. foliaceum endosymbiont retains a prominent nucleus, multiple four-membrane plastids, and mitochondria, all within a relatively large volume of cytoplasm that is separated from the host cytoplasm by a single membrane. Here we report the first protein-coding gene sequences from the K. foliaceum endosymbiont and host nuclear genomes. We have characterised genes for nucleus-encoded cytosolic proteins, actin (from endosymbiont), alpha-tubulin (from both), beta-tubulin (from host), and HSP90 (from both), in addition to homologues from pennate diatoms Nitzschia thermalis and Phaeodactylum tricornutum. Phylogenetic reconstruction shows that the actin is diatom-derived, the beta-tubulin dinoflagellate-derived, while both diatom- and dinoflagellate-derived alpha-tubulin and HSP90 genes were found. The base composition biases of these genes co-varied with their phylogenetic position, suggesting that the genes still reside in their respective genomes. The presence of these genes implies they are still functional and more generally indicates that the endosymbiont is less genetically reduced than those of cryptophytes or chlorarachniophytes, raising the interesting question of whether any genes have transferred between the two nuclear genomes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.2004.tb00604.x
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  • 13
    Electronic Resource
    Electronic Resource
    Molecular Phylogeny and Surface Morphology of Colpodella edax (Alveolata): Insights into the Phagotrophic Ancestry of Apicomplexans (2003)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 50 (2003), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: . The molecular phylogeny of colpodellids provides a framework for inferences about the earliest stages in apicomplexan evolution and the characteristics of the last common ancestor of apicomplexans and dinoflagellates. We extended this research by presenting phylogenetic analyses of small subunit rRNA gene sequences from Colpodella edax and three unidentified eukaryotes published from molecular phylogenetic surveys of anoxic environments. Phylogenetic analyses consistently showed C. edax and the environmental sequences nested within a colpodellid clade, which formed the sister group to (eu)apicomplexans. We also presented surface details of C. edax using scanning electron microscopy in order to supplement previous ultrastructural investigations of this species using transmission electron microscopy and to provide morphological context for interpreting environmental sequences. The microscopical data confirmed a sparse distribution of micropores, an amphiesma consisting of small polygonal alveoli, flagellar hairs on the anterior flagellum, and a rostrum molded by the underlying (open-sided) conoid. Three flagella were present in some individuals, a peculiar feature also found in the microgametes of some apicomplexans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.2003.tb00145.x
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  • 14
    Electronic Resource
    Electronic Resource
    A Transcriptional Fusion of Genes Encoding Glyceraldehyde-3-Phosphate Dehydrogenase (GAPDH) and Enolase in Dinoflagellates (2005)
    Oxford, UK : Blackwell Science Inc
    The @journal of eukaryotic microbiology 52 (2005), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and enolase are enzymes essential for glycolysis and gluconeogenesis. Dinoflagellates possess several types of both GAPDH and enolase genes. Here, we identify a novel cytosolic GAPDH–enolase fusion protein in several dinoflagellate species. Phylogenetic analyses revealed that the GAPDH moiety of this fusion is weakly related to a cytosolic GAPDH previously reported in dinoflagellates, ciliates, and an apicomplexan. The enolase moiety has phylogenetic affinity with sequences from ciliates and apicomplexans, as expected for dinoflagellate genes. Furthermore, the enolase moiety has two insertions in a highly conserved region of the gene that are shared with ciliate and apicomplexan homologues, as well as with land plants, stramenopiles, haptophytes, and a chlorarachniophyte. Another glycolytic gene fusion in eukaryotes is the mitochondrion-targeted triose-phosphate isomerase (TPI) and GAPDH fusion in stramenopiles (i.e. diatoms and oomycetes). However, unlike the mitochondrial TPI–GAPDH fusion, the GAPDH–enolase fusion protein appears to exist in the same compartment as stand-alone homologues of each protein, and the metabolic reactions they catalyze in glycolysis and gluconeogenesis are not directly sequential. It is possible that the fusion is post-translationally processed to give separate GAPDH and enolase products, or that the fusion protein may function as a single bifunctional polypeptide in glycolysis, gluconeogenesis, or perhaps more likely in some previously unrecognized metabolic capacity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.2005.00042x
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  • 15
    Electronic Resource
    Electronic Resource
    Microsporidian Mitochondrial Proteins: Expression in Antonospora locustae Spores and Identification of Genes Coding for Two Further Proteins (2005)
    Oxford, UK : Blackwell Science Inc
    The @journal of eukaryotic microbiology 52 (2005), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. Microsporidia are obligate intracellular parasites, phylogenetically allied to the fungi. Once considered amitochondriate, now a number of mitochondrion-derived genes have been described from various species, and the relict organelle was recently identified in Trachipleistophora hominis. We have investigated the expression of potential mitochondrial targeted proteins in the spore stage to determine whether the organelle is likely to have a role in the spore or early infection stage. To investigate whether the Antonospora locustae genome codes for a different complement of mitochondrial proteins than Encephalitozoon cuniculi an EST library was searched for putative mitochondrial genes that have not been identified in the E. cuniculi genome project. The spore is the infectious stage of microsporidia, but is generally considered to be metabolically dormant. Fourteen genes for putatively mitochondrion-targeted proteins were shown to be present in purified spore mRNA by 3′-rapid amplification of cDNA ends and EST sequencing. Pyruvate dehydrogenase E1α and mitochondrial glycerol-3-phosphate dehydrogenase proteins were also shown to be present in A. locustae and E. cuniculi spores, respectively, suggesting a role for these proteins in the early stages of infection, or within the spore itself. EST sequencing also revealed two mitochondrial protein-encoding genes in A. locustae that are not found in the genome of E. cuniculi. One encodes a possible pyruvate transporter, the other a subunit of the mitochondrial inner membrane peptidase. In yeast mitochondria, this protein is part of a trimeric complex that processes proteins targeted to the inner membrane and the intermembrane space, and its substrate in A. locustae is presently unknown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.2005.05-00036.x
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  • 16
    Electronic Resource
    Electronic Resource
    Filling in the gaps: EST surveys of under-represented chromalveolates (2005)
    Oxford, UK : Blackwell Science Inc
    The @journal of eukaryotic microbiology 52 (2005), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The “chromalveolate hypothesis” posits the monophyly of alveolates (apicomplexans, dinoflagellates and ciliates), heterokonts, haptophytes and cryptomonads. One implication of the monophyly of chromalveolates is that the plastids in this group could share a common ancestor—derived from a single endosymbiosis. Members of all chromalveolate groups, with the exception of ciliates, possess a secondary plastid originating from a rhodophytic symbiont (although the rhodophytic origin of the apicomplexan plastid remains contentious). A single origin of this chromalveolate plastid represents the most parsimonious hypothesis for plastid acquisition. Growing support for the “chromalveolate hypothesis” has relied on a relatively small number of molecular studies to date, and a more thorough examination of this alliance has been undermined by a paucity of broad molecular data from several of its members, despite complete genome sequences from apicomplexans and ciliates. To address this deficit we have undertaken EST (Expressed Sequence Tag) surveys of several taxa, representing dinoflagellates, haptophytes and cryptomonads. Using EST data we are undertaking broad molecular comparisons of these groups through molecular phylogenies, analyses of common biochemical pathways, and studies of organelle evolution. This genome-based approach provides a more complete view of the major chromalveolate groups, and a chance to more thoroughly test the chromalveolate hypothesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.2005.05202003_1_80.x
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  • 17
    Electronic Resource
    Electronic Resource
    Actin and Ubiquitin Protein Sequences Support a Cercozoan/Foraminiferan Ancestry for the Plasmodiophorid Plant Pathogens (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: . The plasmodiophorids are a group of eukaryotic intracellular parasitehd that cause disease in a variety of economically significant crops. Plasmodiophorids have traditionally been considered fungi but have more recently been suggested to be members of the Cercozoa, a morphologically diverse group of amoeboid, flagellate, and amoeboflagellate protists. The recognition that Cercozoa constitute a monophyletic lineage has come from phylogenetic analyses of small subunit ribosomal RNA genes. Protein sequence data have suggested that the closest relatives of Cercozoa are the Foraminifera. To further test a cercozoan origin for the plasmodiophorids, we isolated actin genes from Plasmodiophora brassicae, Sorosphaera veronicae, and Spongospora subterranea, and polyubiquitin gene fragments from P. brassicae and S. subterranea. We also isolated actin genes from the chlorarachniophyte Lotharella globosa. In protein phytogenies of actin, the plasmodiophorid sequences consistently branch with Cercozoa and Foraminifera, and weakly branch as the sister group to the foraminiferans. The plasmodiophorid polyubiquitin sequences contain a single amino acid residue insertion at the functionally important processing point between ubiquitin monomers, the same place in which an otherwise unique insertion exists in the cercozoan and foraminiferan proteins. Taken together, these results indicate that plasmodiophorids are indeed related to Cercozoa and Foraminifera, although the relationships amongst these groups remain unresolved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.2004.tb00172.x
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  • 18
    Electronic Resource
    Electronic Resource
    The Phylogeny of Colpodellids (Alveolata) Using Small Subunit rRNA Gene Sequences Suggests They are the Free-living Sister Group to Apicomplexans (2002)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 49 (2002), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: . In an attempt to reconstruct early alveolate evolution, we have examined the phylogenetic position of colpodellids by analyzing small subunit rDNA sequences from Colpodella pontica Myl'nikov 2000 and Colpodella sp. (American Type Culture Collection 50594). All phylogenetic analyses grouped the colpodellid sequences together with strong support and placed them strongly within the Alveolata. Most analyses showed colpodellids as the sister group to an apicomplexan clade, albeit with weak support. Sequences from two perkinsids, Perkinsus and Parvilucifera, clustered together and consistently branched as the sister group to dinoflagellates as shown previously. These data demonstrate that colpodellids and perkinsids are plesiomorphically similar in morphology and help provide a phylogenetic framework for inferring the combination of character states present in the last common ancestor of dinoflagellates and apicomplexans. We can infer that this ancestor was probably a myzocytotic predator with two heterodynamic flagella, micropores, trichocysts, rhoptries, micronemes, a polar ring, and a coiled open-sided conoid. This ancestor also very likely contained a plastid, but it is presently not certain whether it was photosynthetic, and it is not clear whether extant perkinsids or colpodellids have retained the organelle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.2002.tb00235.x
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  • 19
    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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  • 20
    Electronic Resource
    Electronic Resource
    The selfish pursuit of sex (1995)
    [s.l.] : Nature Publishing Group
    Nature 375 (1995), S. 283-283 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR - No satisfactory explanation for the origin and evolution of sex in eukaryotes has been proposed that is based solely on the selective advantage (to organisms) derived from genetic shuffling, a primary consequence of meiosis1. Several theories do see genetic shuffling as a ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/375283a0
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