Characterization of accumulation of tobacco PR-5 proteins by IEF-immunoblot analysis.
Accumulation of group 5 pathogenesis-related (PR) proteins in tobacco was characterized by immunological analysis combined with isoelectric focusing. This method clearly distinguished 3 subclasses of PR-5 proteins; basic (osmotin), neutral (osmotin-like protein: OLP) and acidic (PR-S). A high accumulation of PR-5 proteins was detected only in root tissues in which neutral osmotin-like protein was mainly accumulated, in addition to a small amount of osmotin. Immunohistochemical analysis revealed that OLP accumulated in the cortex of the root. Cultured tobacco cells accumulated large amounts of neutral PR-5 proteins (OLP) in cells and the acidic form (PR-S) in the medium. Adaptation to salt stress was associated with a higher accumulation of basic PR-5 (osmotin) and less neutral PR-5. In an analysis of the effect of biotic and abiotic stimuli on the synthesis of PR-5 proteins in leaf tissues, ethylene was found to induce a high accumulation of basic and neutral PR-5 proteins. Tobacco mosaic virus (TMV) infection induced accumulation of all major PR-5 proteins, but induction of OLP was less than that of the other isoforms. Systemic induction of PR-5 proteins in upper non-infected leaves was not observed. Salicylate induced only a small accumulation of PR-S. These results indicate that each PR-5 protein has an independent regulatory pathway for its gene expression.
Department of Agricultural Chemistry, Faculty of Agriculture, Kyoto University, Japan.
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H
Koiwa
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Sato
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Yamada
D000595:Amino Acid Sequence; D015151:Immunoblotting; D007150:Immunohistochemistry; D007525:Isoelectric Focusing; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D010947:Plants, Toxic; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism*
D010940:Plant Proteins; C053376:pathogenesis-related proteins, plant; C073139:osmotin protein, Nicotiana tabacum