CELLULASE FROM LEAF ABSCISSION ZONE OF COLEUS

The majority of cellulase activity (beta-1,4-glucan 4-glucanohydrolase , EC 3.2.1.4) from leaf abscission zones of coleus (Coleus blumei) cou ld be extracted by phosphate buffer containing no salt, suggesting a d ifference in the active form of the cellulase in abscission zone of co leus than for the previously reported cellulase in abscission zone of bean plants. Coleus cellulase has an isoelectric point of 4.7 and is p resent only in abscissing tissue. A time course study of abscission an d cellulase activity in abscission zone cells indicated that an increa se in cellulase activity is associated with abscission. Ethylene promo ted cellulase activity whereas indole-3-acetic acid (IAA) inhibited ac tivity in abscission zones compared with the activity in untreated con trols, consistent with the effects of ethylene and LAA on abscission. By native polyacrylamide gel electrophoresis, two cellulase isozymes w ere identified, both of which appeared necessary for abscission.