Effect of Ethylene on the Release of alpha-Amylase through Cell Walls of Barley Aleurone Layers

A large portion of the gibberellic acid (GA₃)-induced α-amylase in isolated aleurone layers is transported into the incubation medium. In the presence of GA₃ and ethylene, an even larger portion of the enzyme is found in the medium. Employing an acid washing technique developed by Varner and Mense (Plant Physiol 1972 49:187-189), it was observed that ethylene significantly reduces the amount of α-amylase trapped by the thick cell walls of aleurone layers. However, the amount of enzyme remaining in the cell (within the boundary of plasma membrane) is not affected by ethylene. Ethylene has no observable effect on membrane formation as measured by the incorporation of ³²P]orthophosphate into phospholipids. Because of these observations it is suggested that ethylene enhances the release of α-amylase, i.e. transport of α-amylase across cell walls, but not the secretion of α-amylase, i.e. transport of α-amylase past the barrier of plasma membrane. The possible mechanism of this ethylene effect is discussed.