Multiplication of Velvet Tobacco Mottle Virus in Nicotiana clevelandii Protoplasts Is Resistant to α-Amanitin

Protoplasts from Nicotiana clevelandii were infected with velvet tobacco mottle virus (VTMoV) using inocula containing 2 µg/ml poly-l-ornithine (PLO), 8 µg/ml VTMoV and 0.02 m-potassium citrate pH 5.0. Typically about 47% of the inoculated protoplasts become infected. The amount of virus particles bound to inoculated protoplasts was increased by a decrease in pH, an increase in PLO concentration or an increase in virus concentration. The one-step growth curve of VTMoV in N. clevelandii protoplasts showed that, although large amounts of virus were synthesized, the multiplication was slower than that published for other viruses. Alpha-amanitin (50 µg/ml) had no effect on the rate of accumulation of virus coat protein or on the synthesis of either RNA species of VTMoV when added to cultures immediately after inoculation.