David W Thornbury

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Helper component (HC-Pro) is a virus-encoded nonstructural protein required for aphid transmission of potyviruses. In the tobacco vein mottling virus (TVMV) polyprotein, HC-Pro represents a 457 residue polypeptide from amino acid position 257 to 713. Previous sequence comparison studies have suggested that mutations of one or two specific amino acid(More)
Specific binding between the coat protein (CP) and the helper component (HC) of the tobacco vein mottling potyvirus (TVMV) was characterized using a protein blotting-overlay protocol. In this in vitro assay, HC interacted with either virions or CP monomers originating from the aphid-transmissible TVMV-AT but not from the non-aphid-transmissible TVMV-NAT.(More)
Potato virus C (PVC), a non-aphid transmissible strain of potato virus Y (PVY), was found to code for a protein (PVC-HC) which is similar in molecular weight and immunological reactivity to the helper component protein of PVY (PVY-HC). PVC-HC, however, was inactive with respect to its ability to effect aphid transmission of either PVC or PVY. The(More)
The hypothesis that loss of aphid transmissibility of potyvirus mutants is due to non-retention of virions in the mouthparts was tested by feeding aphids through membranes on purified virions of aphid transmissible (AT or HAT) and non-aphid-transmissible (NAT) tobacco vein mottling virus (TVMV) or tobacco etch virus (TEV), in the presence of functional(More)
The fungus Magnaporthe oryzae is a serious pathogen of rice and other grasses. Telomeric restriction fragments in Magnaporthe isolates that infect perennial ryegrass (prg) are hotspots for genomic rearrangement and undergo frequent, spontaneous alterations during fungal culture. The telomeres of rice-infecting isolates are very stable by comparison.(More)
Helper component (HC) is a virus-encoded nonstructural protein that is required for transmission of potyviruses by their aphid vectors. As a prelude to studies on the molecular basis of HC activity, a cDNA clone (pPB-3) was constructed that contained the first three cistrons (34 kDa-HC-42 kDa) of the RNA genome of the potyvirus tobacco vein mottling virus,(More)
The genomic RNA of tobacco vein mottling virus (TVMV) was translated in a cell-free system derived from rabbit reticulocytes. Antisera against TVMV coat protein, TVMV cylindrical inclusions, the helper component required for aphid transmission of TVMV, and the 49- and 54-kd nuclear inclusion proteins of tobacco etch virus (TEV) were used to characterize the(More)
Helper component (HC) was purified from tobacco vein mottling (TVMV)- and potato virus Y (PVY)- infected tobacco plants by sucrose gradient fractionation followed by affinity chromatography on oligo(dT)-cellulose and by gel electrophoresis. The subunit apparent molecular weights (M(r)) of the purified HCs were 53,000 (53K) and 58K for TVMV and PVY,(More)
The N-terminal portion (P1-HC-Pro-P3) of the tobacco vein mottling virus (TVMV) polyprotein was expressed in insect cells and larvae by a recombinant baculovirus. The proteases necessary to process this TVMV polyprotein fragment were active in insect cells, since mature P1, HC-Pro and P3 proteins were detected by specific antisera in Western blots. Antisera(More)
Certain plant viruses require a 'helper component' in order to be transmitted by aphids. The helper component for potyviruses is a virus-encoded protein with a subunit molecular weight of between 50,000 and 60,000. Aphid transmission of caulimoviruses is associated with the presence of an 18,000 molecular weight polypeptide. The mode of action of the helper(More)