Infectivity of a mixture of cowpea mosaic virus ribonucleoprotein components

Abstract

The Sb isolate of cowpea mosaic virus (CPMV-Sb) produces two nucleoprotein components in the normal course of an infection. The components, M and B, were separated by zone sucrose gradient centrifugation and were found to be serologically indistinguishable. Mixtures of M and B were more than eight times as infective as would be predicted from the separate local lesion assays of M and B, and the ribonucleic acids isolated from M and B showed a similar activation of infectivity upon mixing. Most individual local infections from unfractionated CPMV-Sb probably originate through a synergistic action of M and B rather than through the action of either M or B alone. The virus preparations from plants inoculated with either M or B all contained both M and B. Three possible mechanisms of infectivity activation are evaluated and compared.