RNA-dependent RNA polymerase of tobacco plants.

Several properties of RNA polymerase (nucleosidetriphosphate:RNA nucleotidyltransferase, EC 2.7.7.6) active fractions obtained from tobacco plants, be they uninfected, infected with tobacco mosaic virus, or infected with tobacco necrosis virus, were compared. By the seven criteria tested, the RNA-dependent RNA polymerase from these three sources behaved the same, although its activity is greatly but variably stimulated by the two virus infections. It thus appears probable that these two viruses do not code for this enzyme, but rely for their replication on their ability to stimulate production of a host enzyme. The conclusion that cells contain RNA replicating capability represents a modification of the central dogma of molecular biology.