The proteins synthesized in tobacco leaves infected with tobacco necrosis virus and satellite tobacco necrosis virus.

Abstract

Abstract The synthesis of radioactively labeled proteins in extracts of infected leaves was studied by polyacrylamide gel electrophoresis in sodium dodecyl sulfate containing buffers. A double labeling technique and treatment of leaves with actinomycin D aided in distinguishing the synthesis of virus-induced or virus-stimulated proteins from the synthesis of host proteins. Six virus-induced or virus-stimulated proteins were detected in leaves infected with tobacco necrosis virus (TNV). In addition to the viral coat protein, proteins of molecular weights 64,000, 42,000, 23,000, 15,000 and 12,000 were resolved. The synthesis of the viral coat protein greatly exceeded that of the nonstructural proteins. The TNV genome is sufficiently large to code for all six proteins detected. Studies of extracts of leaves coinfected with satellite tobacco necrosis virus (STNV) and TNV revealed the synthesis of only one STNV-induced protein, the viral coat protein. When large amounts of STNV coat protein were synthesized, the production of the TNV coat protein of both strains A and B was selectively suppressed. The selective reduction of TNV coat protein synthesis suggested that STNV interference with TNV multiplication is effected at least in part at the translational level.