Effects of Formycin B on Tobacco Mosaic Virus Multiplication

Formycin B (FMB), when applied for 5–6 hr immediately after inoculation, inhibited tobacco mosaic virus (TMV) multiplication in tobacco leaf-discs and local lesion formation on bean leaves. The inhibitory activity of FMB on local lesion formation was reversed by the addition of adenine, adenosine, and adenylic acid of 5 times in molar concentration as much as FMB, but not by hypoxanthine or uracil. FMB-treatment did not cause significant changes in total RNA contents and in the synthetic rates in TMV-inoculated and noninoculated tobacco leaf-discs. However, 32P incorporation rates into TMV and the amount of TMV synthesized in leaf-discs were remarkably reduced by FMB-treatment. 32P-phosphorylated FMB could not be detected either from FMB-treated tobacco leaf RNA or from TMV-RNA by means of column chromatography. 3H-labeled FMB could not be detected in either TMV or in tobacco leaf RNA. The inhibitory action of FMB against TMV multiplication in tobacco leaf-discs is discussed.