Cell-to-cell Transport of Cowpea Mosaic Virus Requires Both the 58K/48K Proteins and the Capsid Proteins

Insertions and deletions have been introduced into an infectious cDNA clone of M RNA of cowpea mosaic virus (CPMV), in the coding regions of the 58K/48K and capsid proteins. Transcripts derived from these mutant clones appeared to be replicated in cowpea protoplasts as detected by immunofluorescent staining and Northern blotting. However in cowpea plants, mutations in either egion restricted the replication of the viral RNAs to the inoculated cells and thus prevented a successful systemic infection of the plant. These results indicate that the M RNA-encoded 58K/48K proteins are involved in cell-to-cell transport of CPMV, and that the virus can spread only if the RNA is encapsidated in particles