Synthesis of Stress Proteins in Tobacco Leaves

Abstract
Pathogenesis-related proteins (PR proteins), which are known to be induced in tobacco leaves in response to infection with tobacco mosaic virus (TMV), were isolated by a simple procedure involving ammonium sulfate fractionation and preparative gel electrophoresis. A rabbit antibody to one of the purified PR proteins, designated as PR1a, also reacted with two other PR proteins, designated as PR1b and PR1c in double immunodiffusion tests. Quantitative analysis of these proteins using rocket immunoelectrophoresis with the antibody showed that they were induced not only by infection with TMV but also by mechanical injury and osmotic stress at 20°C, although not at 30°C. Based on these findings, we propose that these proteins be called “stress proteins” rather than “pathogenesis-related proteins.”