Effect of Ethylene on the Gibberellic Acid-Enhanced Synthesis and Release of Amylase by Isolated Barley Aleurone Layers

Abstract

Methods were developed and extended to enable the incubation of isolated barley (Hordeum vulgare cv. Himalaya) aleurone layers under carefully controlled conditions for studies on effects of ethylene on amylase synthesis and release. When layers in medium containing gibberellic acid were exposed to ethylene, the synthesis and release of amylase were altered relative to layers maintained in an ethylene-free environment. These ethylene effects were detected at the smallest concentration used, 0.041 nl/ml, indicating a very low threshold value. During the initial 24 h, ethylene accelerated both the appearance of total amylase activity, and the release of this activity from the aleurone layers. On the other hand, ethylene reduced the total amount of amylase activity that was recovered from samples after 48 and 72 h.Ethylene did not stimulate the release of amylase from membrane-bound structures within the aleurone layers, and did not interact with the enzyme directly.The isoelectric patterns of amylase activity and proteins released from control and ethylene-treated aleurone layers in 24 h were identical. Therefore, ethylene promoted only quantitative differences in amylase synthesis rather than qualitative differences.