Pathogenesis-related proteins (PR proteins), that are induced in tobacco leaves in hypersensitive response to infection with tobacco mosaic virus (TMV) or by treatment with chemicals, were found to be also inducible in a dedifferentiated system, tobacco suspension culture. Quantitative determination of these proteins using anti PR 1a IgG showed that their increase started at about the end of cell growth period and that their production could be enhanced by the addition of potassium salicylate, Eosin Yellowish and plant hormones (GA3, IAA and 2,4-D). The production depended on the concentration of the chemical inducer and the cell line used. In BY-2 cell line, PR proteins amounted to 12 μg at day 5 and then increased exponentially with time, reaching 280 μg or 70 μg per g fr wt of cells at day 9 with or without the addition of 25 μm potassium salicylate. More than 90% of the induced PR proteins was found in the medium and less than 10% in the cells at day 9. Peroxidase activity in the medium was constant throughout the experiment although total activity in the flask increased with cell growth, indicating that PR proteins are actively secreted into the medium.
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Ohashi et al. (1987) studied this question.