EVIDENCE FOR THE PREFERENTIAL EXPRESSION OF PARTICULAR POLYPEPTIDES IN LEAF ABSCISSION ZONES OF THE BEAN PHASEOLUS-VULGARIS L

Proteins have been extracted from the distal pulvinus: petiole abscission zone and adjacent pulvinus and petiole tissues of primary leaves of Phaseolus vulgaris L. These have been compared by gel electrophoresis and immuno-blotting to determine if the polypeptide profile of the abscission zone differs, either qualitatively or quantitatively, from those of the other two tissues. Enrichment of the abscission zone extract by immuno-absorption with antibodies to petiole and pulvinus extracts has revealed a polypeptide of c. 68 kDa which is prominent only in the abscission zone. By Western blotting and probing with a monoclonal antibody of predetermined specificity, two further polypeptides, of c. 45 kDa and c. 36 kDa, have been shown also to be expressed preferentially in the abscission zone. The c. 36 kDa polypeptide appears to be membrane-bound. The identification of such proteins is discussed with respect to evidence that specific target cells for the plant hormone ethylene are differentiated at the abscission zone. © 1990, Gustav Fischer Verlag, Stuttgart. All rights reserved.