No viral gene is able to elicit RNA-dependent RNA polymerase in cucumber mosaic virus-infected cucumber cotyledons

Infection of cucumber cotyledons by cucumber mosaic virus, a divided genome virus, leads to the early appearance of considerable RNA-dependent RNA polymerase activity. When the genome components were tested separately for this effect, no single one was found active, and different combinations of two components caused varying lesser stimulations than when the three components necessary for infectivity were used. These intermediate effects paralleled the infectivities of these two-component mixtures. It appears probable that the stimulation of enzyme production is the consequence of viral infection, rather than being attributable to one or more viral genes.