Occurrence and Localization of 9.5 Cellulase in Abscising and Nonabscising Tissues

Abstract

Nitrocellulose tissue prints immunoblotted with 9.5 cellulase antibody were used to demonstrate areas of cellulase localization within Phaseolus vulgaris explants on exposure to ethylene. The 9.5 cellulase was induced in the distal and proximal abscission zone and in the stem. In both abscission zones, the 9.5 cellulase was found in the cortical cells of the separation layer, which develops as a narrow band of cells at the place where fracture occurs. The enzyme was also found associated with the vascular traces of the tissues adjacent to the separation layer extending through the first few millimeters at each side of the separation layer. The two abscission zones differed in the way that cellulase distributed through the separation layer as abscission proceeded. In the distal zone, cellulase appeared first in the cells of the separation layer adjacent to vascular traces and extended toward the periphery. In the proximal zone, 9.5 cellulase accumulated first in the cortical cells that lie in the adaxial side and then extended to the abaxial side. In response to ethylene, 9.5 cellulase was also induced in the vascular traces of the stem and the pulvinus without developing a separation layer. The role of 9.5 cellulase in the vascular traces is unknown. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by immunoblotting with 9.5 cellulase antibody identified the same 51-kilodalton protein in both abscising and nonabscising tissues. Therefore, the determinant characteristic of the abscission process is the induction of 9.5 cellulase by cortical cells in the separation layer, and this implies that these cells have a unique mechanism for initiating 9.5 cellulase synthesis.

Identification and Kinetics of Accumulation of Proteins Induced by Ethylene in Bean Abscission Zones

“…The increase in activity of 9.5 cellulase has been correlated with the decrease in break-strength in the separation layer (9). The enzyme occurs in the cortical cells of the separation layer and it is also found associated with the vascular bundles of tissues adjacent to the separation layer (7). Overall, these results indicate that this cellulase plays an important role in abscission.…”

Induction of Enzymes Associated with Lysigenous Aerenchyma Formation in Roots of Zea mays during Hypoxia or Nitrogen Starvation

“…Also as mentioned above, thercr can be no doubt that many degradative enzymes are induced under these co:nditions, and cellulase may increase relatively late in the process of cell lysis. It is interesting to note the parallel between aerenchyma formation and the signaling by ethylene of cell lysis in the leaf abscission zone, which also involves induction of cellulase activity (Horton and Osbome, 1967;de1 Campillo et al, 1990;de1 Campillo and Lewis, 1992).…”

Tissue-Specific Expression of Cell Wall Proteins in Developing Soybean Tissues.

“…soybean tissues. Since they were developed by Cassab and Varner (1987), tissue print immunoblots have been successfully applied to localize cellular and extracellular proteins (Keller et al, 1988;del Campillo et al, 1990;Reid et al, 1990). When the fresh-cut tissue is pressed on the CaCI 2 -pretreated nitrocellulose paper, all soluble and saltsoluble proteins are transferred onto the paper.…”