MULTIPARTITE NATURE OF POTATO VIRUS-X

Potato virus X (PVX) was among the first viruses to be purified. Nonetheless, properties of the purified virus remain contentious. The literature has been heavily influenced by the concept of a virus as a monopartite entity. Despite the fact that electron micrographs invariably show large proportions of shorter virus particles, the latter are universally ignored. Seven distinct classes of particle lengths were detected. Seven RNA species of approximate sizes 6.4, 3.6, 3.0, 2.1, 1.8, 1.4, and 0.9 kb were extracted from these purified virus preparations. This study shows clearly that shorter PVX particles are not breakage products and indicates that they may reflect fundamental properties of the genome strategy. Furthermore, other potexviruses have been found to contain many shorter particles, and the level of these particles is stable during purification. PVX is generally believed to consist of particles of single length even though the literature does not confirm this conclusion. The notion of a single particle length appears to reflect historical concepts of what a virus should be rather than what PVX is. This report considers whether shorter rods present in virus preparations of PVX are distinctive products of infection. The problem addressed is significant because it affects conclusions concerning the mechanisms of PVX biosynthesis and replication.