A mutant of alfalfa mosaic virus with an unusual structure

Competition between the RNA 3 molecules of wildtype alfalfa mosaic virus and the temperature-sensitive mutant Tbts 7(uv)

In mixed infections of wildtype (wt) alfalfa mosaic virus (AMV) and a temperature-sensitive mutant Tbts 7(uv), which carries a thermosensitive defect in the early function of the coat protein, the mutant symptoms were not found at 30°C. In the progeny from these mixed infections almost no mutant coat protein and no mutant RNA 3 could be detected. Even at 23°C there was some loss of mutant RNA 3 and coat protein from the progeny of the mixed infections. Analysis and comparison of mutant and wt ds RNA preparations revealed a lower ds RNA 3 content for the mutant preparation at 23°C. Also the amount of RNA 3 in virion preparations was lower for the mutant than for wt. These results point to a mutation in the RNA 3 of Tbts 7(uv) which diminishes its affinity for the viral replicase.