Localization of ATPase in the endoplasmic reticulum and golgi apparatus of barley aleurone

Abstract

The cytochemical localization of adenosine triphosphatase (ATPase) was studied in the aleurone layer of barley (Hordeum vulgare L. cv. Himalaya). Isolated barley aleurone layers secrete numerous enzymes having acid phosphatase activity, including ATPase. The secretion of these enzymes was stimulated by incubation of the aleurone layer in gibberellic acid (GA3). ATPase was localized using the metal-salt method in tissue incubated in CaCl2 with and without GA3. In sections of tissue incubated without GA3, cytochemical staining was confined to a narrow band of cytoplasm adjacent to the starchy endosperm and to the cell wall of the innermost tier of aleurone cells. Cytochemical staining was absent from the organelles of tissues not treated with GA3. In tissue incubated in the presence of GA3, cytochemical staining was evident throughout the cytoplasm and cell walls of the tissue. In the cell wall, electron-dense deposits were found only in digested channels. The cell-wall matrix of GA3-treated aleurone did not stain, indicating that it does not permit diffusion of enzyme. In the cytoplasm of GA3-treated aleurone, all organelles except microbodies, plastids, and spherosomes stained for ATPase activity; endoplasmic reticulum (ER), Golgi apparatus, and mitochondria showed intense deposits of stain. The ER of the aleurone is a complex system made up of flattened sheets of membrane, which may be associated with both the Golgi apparatus and the plasma membrane. The dictyosome did not stain uniformly for ATPase activity; rather there was a gradation in staining of the cisternae from thecis (lightly stained) to thetrans (heavily stained) face. Vesicles associated with dictyosome cisternae also stained intensely as did the protein bodies of GA3-treated aleurone cells.