RNA-dependent RNA Polymerase Activities in Tomato Plants Susceptible or Resistant to Tobacco Mosaic Virus

Abstract

RNA-dependent RNA polymerase activities were measured in healthy and tobacco mosaic virus (TMV)-infected tomato plants, to investigate the possibility that altered activity might be involved in the operation of the Tm-I gene for resistance to TMV. Healthy, susceptible and resistant plants had similar levels of enzyme activity. Infection with TMV strain 0, which is inhibited by Tm-I, caused a 2-fold increase in activity in susceptible plants but no increase in Tm-I plants. Infection with a number of strain 1 isolates, which overcome Tm-I resistance, led to a 2 to 4-fold increase in enzyme activity in resistant plants.