Characterization of Polypeptides that Accumulate in Cultured Nicotiana tabacum Cells

We characterized the polypeptides that accumulate in photoautotrophically cultured cells of tobacco. Microsequencing of these polypeptides accumulated in large amounts revealed four NH2-terminal amino acid sequences that were highly homologous to those of the known stress proteins, osmotin and chitinase. Further analyses of our tobacco cell line grown with sucrose in light and in darkness, as well as analyses of newly established cultured cells and regenerating adventitious shoots, clearly showed that all the in vitro cultured cells accumulated these stress proteins. The accumulation of these proteins were also observed in old leaves, roots, and leaves infected with Tobacco Mosaic Virus, but not in young healthy leaves.