Linear Biosynthesis of Tobacco Mosaic Virus: Evidence That Short Virus Rods Are Natural Products of TMV Biosynthesis

Abstract

This paper considers whether the ribonucleoprotein rods that are the distinctive product of the tobacco mosaic virus (TMV) infection process are inherently variable in length. The problem is of interest because it influences conclusions regarding the mechanisms of TMV biosynthesis and replication.In previous studies of the incorporation of C14 into TMV in the infected tobacco leaf we have shown that the virus protein and RNA components are synthesized concurrently from the leaf's pools of free amino acids and ribonucleotides.' This observation, which has now been confirmed in two other RNA-bearing viruses, poliovirus2 and fowl plague virus,3 mitigates against the possible occurrence of free RNA and protein precursors of TMV, and suggests instead that incomplete or alternative forms of the virus are more likely to consist of ribonucleoprotein. Since the virus' protein subunits and RNA fiber form coaxial structures in the TMV rod, any ribonucleoprotein alternative to the predominant 3,000 A rod is likely to take the form of a rod of some different length.The problem of TMV rod length has been the subject of considerable study, but there is little agreement as to the significance of the results. While it is now clear that rods longer than 3,000 A are preparative artefacts,4 5 there is wide disagreement regarding the origin of the rods shorter than 3,000 A that are always observed in TMV preparations. Two recent reviews of this question reach opposite conclusions. Pirie6 supports the view that short rods are natural products of TMV bio-

Fluctuating Asymmetry: Methods, Theory, and Applications

“…Nevertheless, some studies have examined within-genotype variation. Commoner [283] and colleagues, including Symington et al [284], examined variation in length of the Tobacco Mosaic Virus, a helical RNA virus. The rods vary greatly in length, from 50-600 mμ.…”

“…The modal length is 300 mμ. Rods longer than 300 mμ arise by polymerization during preparation, but most of the rods measuring less than 300 mμ are due to natural biosynthetic variation, not in vivo breakage during preparation for electron microscopy [284]. The short rods probably represent aborted forms of the virus [283], and they make up much of the population.…”

The Use of a Replicating Virus Vector For in Planta Generation of Tobacco Mosaic Virus Nanorods Suitable For Metallization

“…Transmission electron microscopy of the purified CP/OAS and CP/VP60/OAS nanorods showed they had a similar morphology to natural TMV ( Symington et al, 1962 ), but exhibiting variations in length ( Figure 2B ). Nanorod length heterogenicity was seen particularly in the CP/OAS sample.…”

Multipartite nature of potato virus X

“…Two experiments addressed the possibility of particle shearing during purification (38). Rod length frequency distributions of a standard purified virus preparation were compared with those of the original unpurified Rod length frequency distributions of PVX observed after purification by the procedure described in the text (A) and the original extract after grinding infected leaf tissue with a mortar and pestle (B).…”

“…shorter rods of TMV and PVX were not infectious, many researchers regarded them as purification artifacts. Years later, TMV strains were shown to contain particles with subgenomic RNAs (6,9,15,16,29,30,31,38). However, the smaller particles of PVX were never examined.…”