Viruses of Eucaryotic Microorganisms

Lemke, Paul A.

doi:10.1146/annurev.mi.30.100176.000541

Cited by 100 publications

(26 citation statements)

References 84 publications

(124 reference statements)

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“…The presence of VLP caused disintegration of host cells and may also have interfered with zoospore multiplication when released into culture medium. Similar polygonal VLP have been observed in eucaryotic algae (Lemke 1976, Dodds 1979, Dodds & Cole 1980, Van Etten et al 1981. However, the lack of the characterization of these VLP does not permit their classification.…”

Section: Discussionsupporting

confidence: 56%

“…The occurrence of viruses and virus-like particles (VLP) among eucaryotic algae, lower fungi and protozoan species was reported by Lemke (1976), who recorded an extensive List of eucaryotic algae in which viruses and VLP have been observed. In addition several reviews on algal viruses have been written (Sherman & Brown 1978, Dodds 1979, Lauckner 1983.…”

Section: Introductionmentioning

confidence: 94%

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Virus-like particles in Perkinsus atlanticus (Apicomplexa, Perkinsidae)

Azevedo¹

1990

Dis. Aquat. Org.

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Virus-like particles (VLP) were observed in different phases of the in vitro zoosporulation of Perkinsus atlanticus (Apicomplexa, Perlunsidae) which parasitized the gill tissues of Rudtapes decussatus (Molluscs, Bivalvia). These VLP were represented by numerous electron-dense bodies (ca 125 nm diameter) not previously described in similar culture processes. The VLP were densely packed in a membrane-lined inclusion of isolated host-cell cytoplasm of parasitic origin. They were also found among prezoosporangia and zoosporangia of P. atlanticus, a species that causes recurrent mortalities in the clam R. decussatus. The ultrastructural organization of these VLP seems to represent a new and unclassified virus of P. atlanticus.

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Section: Discussionsupporting

confidence: 56%

Section: Introductionmentioning

confidence: 94%

Virus-like particles in Perkinsus atlanticus (Apicomplexa, Perkinsidae)

Azevedo¹

1990

Dis. Aquat. Org.

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“…The suppressive strains T132B NK 17, 19, and 20 lacked the M-dsRNA of the killer, but they had the smaller RNA species designated Si, S3, and S4, respectively. The sizes (mean ± SD) of the dsRNAs, determined under the conditions of electron microscopy used, are 1.83 + 0.05 (n = 173), § 1.50 + 0.05 (n = 194), 1.40 + 0.06 (n = 228), and 0.73 ± 0.04 kb (n = 191) for M, S1, S4, and S3. These sizes agree with the molecular weights determined previously under different conditions of electron microscopy (7).…”

Section: Resultsmentioning

confidence: 99%

Electron microscopic heteroduplex analysis of "killer" double-stranded RNA species from yeast.

Fried¹,

Fink²

1978

Proc. Natl. Acad. Sci. U.S.A.

160

110

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Wild-type and mutant double-stranded RNA (dsRNA) species from the yeast Saccharomyces cerevisiae were studied by electron microscopic heteroduplex mapping to determine the sequence relationships among the different RNA molecules. Three mutant dsRNAs, 1.5, 1.4, and 0.73 kilobase, were found to be derived by the same internal deletion of the wild-type (1.83 kilobases) molecule. This deletion includes a segment of about 200 base pairs that was estimated to be nearly 100% A + U. In addition, the sequences of the two larger mutant RNA species are tandem, direct duplications. One of the duplicated molecules appears to have a second internal deletion that occurred after the duplication. The mutant dsRNAs are functionally similar to the defective interfering virus particles of anima viruses all of the mutant species prevent the propagation of the wild-type dsRNA when both are present in the same cell. The four dsRNAs share the same sequences at their termini, a finding that may suggest that these sequences are important for the replication of the dsRNAs.Viruses and virus-like particles containing double-stranded RNA (dsRNA) are common to many species of fungi (1). Killer strains of the yeast Saccharomyces cerevisiae possess viral particles with two separately encapsidated dsRNA species: large (L), 2.5 X 106 daltons; and medium (M), 1.18 X 106 daltons (see refs. 2 and 3 for recent reviews). These strains excrete a toxic protein that kills sensitive strains but not killer strains. The M-dsRNA was believed to produce toxin and immunity to toxin because (i) the non-Mendelian segregation of these two killer traits is paralleled by cytoplasmic transmission of the dsRNA, and (ii) strains with an alteration in either toxin production or immunity either lack the M-dsRNA or have an altered form of it (4, 5). Recently, in vitro translation experiments have proved that M encodes the killer toxin (J. Hopper, personal communication). Denatured M-dsRNA directed the synthesis of a protein that, although larger than killer toxin, crossreacted with antiserumto toxin and contained all of the tryptic peptides of toxin produced in vivo. In similar in vitro experiments, the L-dsRNA directed the synthesis of the major capsid protein of the virus-like particles (6).Nonkiller mutants have been isolated that lack the M-dsRNA but have smaller (S) dsRNA species (7). When these mutants are mated to a killer strain the S-dsRNAs prevent or "suppress" the propagation of the M-dsRNA in the resulting diploids. With continued growth, the diploid cells rapidly become nonkillers and the M-dsRNA can no longer be detected. These suppressive S-dsRNAs therefore, are analogous to defective interfering virus particles, the subgenomic nucleic acid species of animal viruses that limit the replication of the standard virus during co-infection (8).This report describes electron microscopic heteroduplex mapping experiments between the M-and S-dsRNAs. The 4224 heteroduplexes studied show that the S-dsRNAs arose by deletions of M-dsRNA sequences. The various S-...

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“…The history and ecological aspects of algal viruses can be found in other reviews (35,101,132,178,190,(207)(208)(209)224). This review focuses mainly on the properties of the chlorella viruses, primarily PBCV-1.…”

Section: Introductionmentioning

confidence: 99%

Unusual Life Style of Giant Chlorella Viruses

Etten

2003

Annu. Rev. Genet.

175

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Paramecium bursaria chlorella virus (PBCV-1) is the prototype of a family of large, icosahedral, plaque-forming, dsDNA viruses that replicate in certain unicellular, eukaryotic chlorella-like green algae. Its 330-kb genome contains ~373 protein-encoding genes and 11 tRNA genes. The predicted gene products of ~50% of these genes resemble proteins of known function, including many that are unexpected for a virus, e.g., ornithine decarboxylase, hyaluronan synthase, GDP-D-mannose 4,6 dehydratase, and a potassium ion channel protein. In addition to their large genome size, the chlorella viruses have other features that distinguish them from most viruses. These features include: (a) The viruses encode multiple DNA methyltransferases and DNA site-specific endonucleases. (b) The viruses encode at least some, if not all, of the enzymes required to glycosylate their proteins. (c) PBCV-1 has at least three types of introns, a self-splicing intron in a transcription factorlike gene, a spliceosomal processed intron in its DNA polymerase gene, and a small intron in one of its tRNA genes. (d) Many chlorella virus-encoded proteins are either the smallest or among the smallest proteins of their class. (e) Accumulating evidence indicates that the chlorella viruses have a very long evolutionary history.

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Viruses of Eucaryotic Microorganisms

Cited by 100 publications

References 84 publications

Virus-like particles in Perkinsus atlanticus (Apicomplexa, Perkinsidae)

Virus-like particles in Perkinsus atlanticus (Apicomplexa, Perkinsidae)

Electron microscopic heteroduplex analysis of "killer" double-stranded RNA species from yeast.

Unusual Life Style of Giant Chlorella Viruses

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