The major proteins in extracts of tobacco leaves that are responding hypersensitively to virus-infection

Extracts from the leaves of tobacco plants which are reacting hypersensitively to TMV-infection, contain the four ‘novel’ pathogenesis-related (PR-) proteins, and seven other major protease-resistant proteins which are absent or present in small amounts in uninfected leaves, and which can be separated and characterized by electrophoresis and chromatofocusing. None of the seven contain the protein subunit which characterised PR-Ia, b and c. Three of them may be lectins; they stain as if they contained carbohydrate and are absorbed onto chitin. If leaves of infected plants are exposed to 14CO, as lesions develop, PR's-Ia,Ib,Ic,II and one of the other proteins accumulate radioactivity, although it is not clear if they are actively ‘turning over’.