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At least 19 recordsLinked to original sources
PubMed1989

Applying the species concept to plant viruses.

Plant virologists who maintain that the concept of species cannot be applied to viruses argue their case in terms of an obsolete concept of biological species defined by gene pools and reproductive isolation and applicable only to sexually reproducing organisms. In fact, various species concepts have been used by biologists and some of them are applicable to asexual organisms. The rationale for applying the species concept in virology is that viruses are biological entities and not chemicals: they possess genes, replicate, specialize, evolve and occupy specific ecological niches. The following definition is proposed: a virus species is a polythetic class of viruses constituting a replicating lineage and occupying a particular ecological niche. Such a definition of the species category does not and cannot provide a list of diagnostic properties for recognizing members of a particular virus species. It should also be stressed that a single property such as an arbitrary level of genome homology or the extent of serological relationship always fails to establish membership in a polythetic class. A binomial system of nomenclature is advocated in which the vernacular English name of the plant virus is adopted as the species name and the group name is assimilated to the level of genus. Adoption of this system would ensure that a universal classification system based on the classical categories of species, genus, and family becomes possible for all viruses.

Phylogeny↗
PubMed1995

Resistance against multiple plant viruses in plants mediated by a double stranded-RNA specific ribonuclease.

Many plant viruses have single-stranded RNAs as their genomes. During the course of replication, genomic RNAs and their complementary template RNAs are likely to form double-stranded (ds) RNA at least transiently. To attack replication intermediates of many plant RNA viruses specifically, we introduced a yeast-derived ds-RNA specific RNase gene called pac 1 into plants. The transformed plants showed a decrease in lesion numbers when they were challenged with tomato mosaic virus, and a delay in the appearance of symptoms when inoculated with cucumber mosaic virus or potato virus Y.

Mosaic Viruses↗
PubMed1982

Electro-blot radioimmunoassay of virus-infected plant sap - a powerful new technique for detecting plant viruses.

A new technique for detecting viruses in plant sap is described. It consists of sodium dodecyl sulphate-polyacrylamide gel electrophoresis of the infected plant sap, electrophoretic transfer of protein bands to activated paper by the Electro-Blot technique, the subsequent probing of the viral coat protein band by specific antiserum (prepared against intact virus), and detection of immune complex with 125 I-labelled protein A. The technique successfully detected tobacco mosaic virus at a sap dilution of 1 : 10,000, four strains of sugarcane mosaic virus (a potyvirus) in their perennial hosts infected for about 4 years, and five different isolated of potato leaf roll virus (a luteovirus). The latter virus occurs in extremely low concentration and is difficult to detect by the other known methods.

Electrophoresis, Polyacrylamide Gel↗
PubMed1999

HSP70 homolog functions in cell-to-cell movement of a plant virus.

Plant closteroviruses encode a homolog of the HSP70 (heat shock protein, 70 kDa) family of cellular proteins. To facilitate studies of the function of HSP70 homolog (HSP70h) in viral infection, the beet yellows closterovirus (BYV) was modified to express green fluorescent protein. This tagged virus was competent in cell-to-cell movement, producing multicellular infection foci similar to those formed by the wild-type BYV. Inactivation of the HSP70h gene by replacement of the start codon or by deletion of 493 codons resulted in complete arrest of BYV translocation from cell to cell. Identical movement-deficient phenotypes were observed in BYV variants possessing HSP70h that lacked the computer-predicted ATPase domain or the C-terminal domain, or that harbored point mutations in the putative catalytic site of the ATPase. These results demonstrate that the virus-specific member of the HSP70 family of molecular chaperones functions in intercellular translocation and represents an additional type of a plant viral-movement protein.

Adenosine Triphosphatases↗
PubMed1967

Potato spindle tuber virus: a plant virus with properties of a free nucleic acid.

Infectious entities, extractable, with phosphate buffer, from tissue infected with potato spindle tuber virus and inciting symptoms on tomato that are typical of this virus, have properties incompatible with those of conventional virus particles. The infectious particles sediment in sucrose density gradients at approximately the same rate as particles with a sedimentation coefficient of 10S, are insensitive to treatment with organic solvents, and can be concentrated by ethanol precipitation. Treatment with phenol changes neither their infectivity nor their sedimentation properties. Infectivity is insensitive to deoxyribonuclease, but at low ionic strength it is sensitive to ribonuclease. At high ionic strength, infectivity partially survives incubation with ribonuclease. These properties, as well as elution patterns from columns of methylated serum albumin, suggest that the extractable infectious agent may be a double-stranded RNA.

Centrifugation, Density Gradient↗
PubMed1986

Evidence that the amino acid composition of the particle proteins of plant viruses is characteristic of the virus group. I. Multidimensional classification of plant viruses.

The amino acid (AA) contents of the coat proteins of 134 plant viruses and strains were classified by principal components analysis. The virus groupings that were obtained correlated well with the classification of Matthews. The relationships of each virus were dependent on the number of AA residues (axis 1) and on the percentage composition of each AA in the proteins (axes 2-4). The classification indicated which data were anomalous and needed confirmation. There seemed to be more anomalies in estimates of protein size than of protein composition.

Amino Acids↗
PubMed1997

Mechanisms of plant virus evolution.

Plant viruses utilize several mechanisms to generate the large amount of genetic diversity found both within and between species. Plant RNA viruses and pararetroviruses probably have highly error prone replication mechanisms, that result in numerous mutations and a quasispecies nature. The plant DNA viruses also exhibit diversity, but the source of this is less clear. Plant viruses frequently use recombination and reassortment as driving forces in evolution, and, occasionally, other mechanisms such as gene duplication and overprinting. The amount of variation found in different species of plant viruses is remarkably different, even though there is no evidence that the mutation rate varies. The origin of plant viruses is uncertain, but several possible theories are proposed. The relationships between some plant and animal viruses suggests a common origin, possibly an insect virus. The propensity for rapid adaptation makes tracing the evolutionary history of viruses difficult, and long term control of virus disease nearly impossible, but it provides an excellent model system for studying general mechanisms of molecular evolution.

Journal Article↗
PubMed2003

Investigative proteomics: identification of an unknown plant virus from infected plants using mass spectrometry.

We describe the identification of a previously uncharacterized plant virus that is capable of infecting Nicotiana spp. and Arabidopsis thaliana. Protein extracts were first prepared from leaf tissue of uninfected tobacco plants, and the proteins were visualized with two-dimensional electrophoresis (2-DE). Matching gels were then run using protein extracts of a tobacco plant infected with tobacco mosaic virus (TMV). After visual comparison, the proteins spots that were differentially expressed in infected plant tissues were cut from the gels and analyzed by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Tandem mass spectrometry data of individual peptides was searched with SEQUEST. Using this approach we demonstrated a successful proof-of-concept experiment by identifying TMV proteins present in the total protein extract. The same procedure was then applied to tobacco plants infected with a laboratory viral isolate of unknown identity. Several of the differentially expressed protein spots were identified as proteins of potato virus X (PVX), thus successfully identifying the causative agent of the uncharacterized viral infection. We believe this demonstrates that HPLC-MS/MS can be used to successfully characterize unknown viruses in infected plants.

Amino Acid Sequence↗
PubMed1992

Microwave enhanced staining for plant virus inclusions.

Plant virus inclusion bodies can be stained specifically with established staining methods for light microscopy. The procedure can be augmented by a short microwave treatment to provide better staining intensity and reduced staining time. The method is useful for preliminary sampling prior to collection for electron microscopy and for plant pathologists, plant breeders, and diagnosticians as a rapid means of plant virus characterization.

Azure Stains↗
PubMed1994

Early events in virus-plant interactions.

1. Plant viruses can only enter their host through a wounded plant cell. Once in the cytoplasm, the virion must be disassembled, and for certain viruses with a "+" RNA genome, cotranslational disassembly of virus particles has been described. 2. Subsequent to viral protein synthesis which requires the host translational machinery, the "+" RNA genome is replicated in the cytoplasm. Viral genome amplification requires at least one viral-coded non-structural protein in conjunction with one or more host factors. 3. Early events in virus infection can be studied in systems that hinder these events. This is the case of natural hosts that are resistant to viruses: mutant viruses which overcome such resistance have been described. It is also the case of genetically engineered plants that are protected from virus infection. Both types of systems should help in determining the mode of interaction involved, and possibly also the host factor(s) involved in the various steps of virus infection.

Capsid↗
PubMed1995

Broad resistance to plant viruses in transgenic plants conferred by antisense inhibition of a host gene essential in S-adenosylmethionine-dependent transmethylation reactions.

S-Adenosylhomocysteine hydrolase (SAHH) is a key enzyme in transmethylation reactions that use S-adenosylmethionine as the methyl donor. Because of the importance of SAHH in a number of S-adenosylmethionine-dependent transmethylation reactions, particularly the 5' capping of mRNA during viral replication, SAHH has been considered as a target of potential antiviral agents against animal viruses. To test the possibility of engineering a broad type of resistance to plant viruses, we expressed the antisense RNA for tobacco SAHH in transgenic tobacco plants. As expected, transgenic plants constitutively expressing an anti-sense SAHH gene showed resistance to infection by various plant viruses. Among those plants, about half exhibited some level of morphological change (typically stunting). Analysis of the physiological change in those plants showed that they contained excess levels of cytokinin. Because cytokinin has been found to induce acquired resistance, there is also a strong possibility that the observed resistance was induced by cytokinin.

Journal Article↗
PubMed1986

Evidence that the amino acid composition of the particle proteins of plant viruses is characteristic of the virus group. II. Discriminant analysis according to structural biological and classification properties of plant viruses.

The amino acid composition (AAC) of the coat proteins (CPs) of 126 plant viruses or strains were analyzed by stepwise discriminant analysis. The criteria chosen for discrimination were: the structure of virus particles (3 clusters); the mode of of transmission of the viruses (6 clusters); and the grouping of viruses according to the classification of the International Committee on Taxonomy of Viruses (23 groups). Statistically significant correlations were obtained with different groups of discriminant amino acids. The results confirm that the AAC of the CPs contains all the information needed for a quantitative classification of plant viruses. These results and possible explanations of these clustering patterns are discussed.

Amino Acids↗