Polysomes containing infecting viral genome in tobacco leaves infected with tobacco mosaic virus.

Abstract

This study concerns the interaction between parental virus RNA and host cell components in tobacco leaves infected with tobacco mosaic virus (TMV). By using a gentle method for disruption, extracts were obtained from tobacco leaves infected with 32P-labelled TMV and the fate of infecting parental 32P-TMV-RNA was studied. Sucrose gradient centrifugation analysis showed that the parental 32P-RNA distributed into four regions: free RNA, partially uncoated TMV, TMV and a structure heavier than TMV. The heavier structure was considered to be polysomes carrying the parental TMV-RNA as messenger RNA based on its size, sensitivity to RNase, dependence of its formation on protein synthesis and the kinetics of its appearance after infection. Control experiments were done to exclude the possibility that the structure is not an artifact aggregate produced by an interaction between partially uncoated virus or its RNA and host cell components. Polysomes containing TMV-RNA were found as membrane bound forms. Based on these data, it is suggested that uncoating of TMV and formation of polysomes are closely related and evidence has been obtained which suggests that uncovering of the viral genome and its translation takes place hand-in-hand on a single virion.