TMV protein synthesis is not translationally regulated by heat shock

Summary Tobacco mosaic virus (TMV) protein synthesis in tobacco leaf tissue was not translationally regulated under conditions of heat shock as were most of the other proteins that were produced at 25°C. Upon shift from 25°C to 37–40°C, most host protein synthesis was inhibited followed by initiation of synthesis of heat shock proteins. In contrast, TMV protein synthesis continued after the temperature shift. This phenomenon allowed the enhancement of detection of TMV protein synthesis in tobacco leaves. The most prominent proteins labeled were viral when tissue was labeled during the first hr following the shift to 40°C, a period after heat shock repression of host protein synthesis, but before the onset of most heat shock protein synthesis. Another method to predominately label viral proteins was to incubate infected leaves for periods at 35°C which induced repression of preexisting host protein synthesis without inducing synthesis of heat shock proteins.