55 research outputs found
Cellular chaperones and folding enzymes are vital contributors to membrane bound replication and movement complexes during plant RNA virus infection
Cellular chaperones and folding enzymes play central roles in the formation of positive-strand and negative-strand RNA virus infection. This article examines the key cellular chaperones and discusses evidence that these factors are diverted from their cellular functions to play alternative roles in virus infection. For most chaperones discussed, their primary role in the cell is to ensure protein quality control. They are system components that drive substrate protein folding, complex assembly or disaggregation. Their activities often depend upon co-chaperones and ATP hydrolysis. During plant virus infection, Hsp70 and Hsp90 proteins play central roles in the formation of membrane-bound replication complexes for certain members of the tombusvirus, tobamovirus, potyvirus, dianthovirus, potexvirus, and carmovirus genus. There are several co-chaperones, including Yjd1, RME-8, and Hsp40 that associate with the bromovirus replication complex, pomovirus TGB2, and tospovirus Nsm movement proteins. There are also examples of plant viruses that rely on chaperone systems in the endoplasmic reticulum (ER) to support cell-to-cell movement. TMV relies on calreticulin to promote virus intercellular transport. Calreticulin also resides in the plasmodesmata and plays a role in calcium sequestration as well as glycoprotein folding. The pomovirus TGB2 interacts with RME-8 in the endosome. The potexvirus TGB3 protein stimulates expression of ER resident chaperones via the bZIP60 transcription factor. Up-regulating factors involved in protein folding may be essential to handling the load of viral proteins translated along the ER. In addition, TGB3 stimulates SKP1 which is a co-factor in proteasomal degradation of cellular proteins. Such chaperones and co-factors are potential targets for antiviral defense.Peer reviewedEntomology and Plant Patholog
Greenhouse propagation of ornamental cannas grown from rhizomes or seeds
The Oklahoma Cooperative Extension Service periodically issues revisions to its publications. The most current edition is made available. For access to an earlier edition, if available for this title, please contact the Oklahoma State University Library Archives by email at [email protected] or by phone at 405-744-6311
Introduction to Special Issue of Molecular Plant Pathology - "Extracellular and intracellular perception of plant viruses"
Non peer reviewe
Soilborne wheat mosaic virus (SBWMV) 19K protein belongs to a class of cysteine rich proteins that suppress RNA silencing
Amino acid sequence analyses indicate that the Soilborne wheat mosaic virus (SBWMV) 19K protein is a cysteine-rich protein (CRP) and shares sequence homology with CRPs derived from furo-, hordei-, peclu- and tobraviruses. Since the hordei- and pecluvirus CRPs were shown to be pathogenesis factors and/or suppressors of RNA silencing, experiments were conducted to determine if the SBWMV 19K CRP has similar activities. The SBWMV 19K CRP was introduced into the Potato virus X (PVX) viral vector and inoculated to tobacco plants. The SBWMV 19K CRP aggravated PVX-induced symptoms and restored green fluorescent protein (GFP) expression to GFP silenced tissues. These observations indicate that the SBWMV 19K CRP is a pathogenicity determinant and a suppressor of RNA silencing
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Debilitation of Plant Potyvirus Infectivity by P1 Proteinase-Inactivating Mutations and Restoration by Second-Site Modifications
Tobacco etch virus (TEV) encodes three proteinases that catalyze processing of the genome-encoded polyprotein.
The P1 proteinase originates from the N terminus of the polyprotein and catalyzes proteolysis between
itself and the helper component proteinase (HC-Pro). Mutations resulting in substitution of a single amino
acid, small insertions, or deletions were introduced into the P1 coding sequence of the TEV genome. Deletion
of the N-terminal, nonproteolytic domain of P1 had only minor effects on virus infection in protoplasts and
whole plants. Insertion mutations that did not impair proteolytic activity had no measurable effects regardless
of whether the modification affected the N-terminal nonproteolytic or C-terminal proteolytic domain. In
contrast, three mutations (termed S256A, F, and Ī304) that debilitated P1 proteolytic activity rendered the
virus nonviable, whereas a fourth proteinase-debilitating mutation (termed C) resulted in a slow-infection
phenotype. A strategy was devised to determine whether the defect in the P1 mutants was due to an inactive
proteinase domain or due simply to a lack of proteolytic maturation between P1 and HC-Pro. Sequences coding
for a surrogate cleavage site recognized by the TEV NIa proteinase were inserted into the genome of each
processing-debilitated mutant at positions that resulted in NIa-mediated proteolysis between P1 and HC-Pro.
The infectivity of each mutant was restored by these second-site modifications. These data indicate that P1
proteinase activity is not essential for viral infectivity but that separation of P1 and HC-Pro is required. The
data also provide evidence that the proteinase domain is involved in additional, nonproteolytic functions
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Evidence that the Potyvirus P1 Proteinase Functions in trans as an Accessory Factor for Genome Amplification
The tobacco etch potyvirus (TEV) polyprotein is proteolytically processed by three viral proteinases (NIa,
HC-Pro, and P1). While the NIa and HC-Pro proteinases each provide multiple functions essential for viral
infectivity, the role of the P1 proteinase beyond its autoproteolytic activity is understood poorly. To determine
if P1 is necessary for genome amplification and/or virus movement from cell to cell, a mutant lacking the entire
P1 coding region (ĪP1 mutant) was produced with a modified TEV strain (TEV-GUS) expressing Ī²-glucuronidase
(GUS) as a reporter, and its replication and movement phenotypes were assayed in tobacco protoplasts
and plants. The ĪP1 mutant accumulated in protoplasts to approximately 2 to 3% the level of parental
TEV-GUS, indicating that the P1 protein may contribute to but is not strictly required for viral RNA
amplification. The ĪP1 mutant was capable of cell-to-cell and systemic (leaf-to-leaf) movement in plants but
at reduced rates compared with parental virus. This is in contrast to the S256A mutant, which encodes a
processing-defective P1 proteinase and which was nonviable in plants. Both ĪP1 and S256A mutants were
complemented by P1 proteinase expressed in a transgenic host. In transgenic protoplasts, genome amplification
of the ĪP1 mutant relative to parental virus was stimulated five- to sixfold. In transgenic plants, the level
of accumulation of the DP1 mutant was stimulated, although the rate of cell-to-cell movement was the same as
in nontransgenic plants. Also, the S256A mutant was capable of replication and systemic infection in P1-
expressing transgenic plants. These data suggest that, in addition to providing essential processing activity, the
P1 proteinase functions in trans to stimulate genome amplification
Beet necrotic yellow vein virus accumulates inside resting spores and zoosporangia of its vector Polymyxa betae BNYVV infects P. betae
BACKGROUND: Plasmodiophorids and chytrids are zoosporic parasites of algae and land plant and are distributed worldwide. There are 35 species belonging to the order Plasmodiophorales and three species, Polymyxa betae, P. graminis, and Spongospora subterranea, are plant viral vectors. Plasmodiophorid transmitted viruses are positive strand RNA viruses belonging to five genera. Beet necrotic yellow vein virus (BNYVV) and its vector, P. betae, are the causal agents for rhizomania. RESULTS: Evidence of BNYVV replication and movement proteins associating with P. betae resting spores was initially obtained using immunofluorescence labeling and well characterized antisera to each of the BNYVV proteins. Root cross sections were further examined using immunogold labeling and electron microscopy. BNYVV proteins translated from each of the four genomic and subgenomic RNAs accumulate inside P. betae resting spores and zoospores. Statistical analysis was used to determine if immunolabelling detected viral proteins in specific subcellular domains and at a level greater than in control samples. CONCLUSION: Virus-like particles were detected in zoosporangia. Association of BNYVV replication and movement proteins with sporangial and sporogenic stages of P. betae suggest that BNYVV resides inside its vector during more than one life cycle stage. These data suggest that P. betae might be a host as well as a vector for BNYV
Concurrent Suppression of Virus Replication and Rescue of Movement-Defective Virus in Transgenic Plants Expressing the Coat Protein of Potato Virus X
AbstractA line of transgenic tobacco expressing the coat protein (CP) of potato virus X (PVX) was resistant against a broad spectrum of PVX strains. Inoculation of leaves and protoplasts with PVX expressing the jellyfish green fluorescent protein reporter gene revealed that this resistance mechanism suppressed PVX replication in the initially infected cell and systemic spread of the virus. Cell-to-cell movement was also slower in the resistant plants. The resistance at the level of replication was effective against wild-type PVX and also against movement-defective isolates with a frameshift mutation or deletion in the CP ORF. However, the cell-to-cell movement defect of the mutant viruses was rescued on the resistant plants. Based on these results it is proposed that the primary resistance mechanism is at the level of replication
Plant viruses infecting cannas
The Oklahoma Cooperative Extension Service periodically issues revisions to its publications. The most current edition is made available. For access to an earlier edition, if available for this title, please contact the Oklahoma State University Library Archives by email at [email protected] or by phone at 405-744-6311
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