Spatio-temporal appearance of α-amylase and limit dextrinase in barley aleurone layer in response to gibberellic acid, abscisic acid and salicylic acid.

Abstract

Cereal seed germination involves mobilization of storage reserves in the starchy endosperm to support seedling growth. In response to gibberellin produced by the embryo the aleurone layer synthesizes hydrolases that are secreted to the endosperm for degradation of storage products. In this study analysis of intracellular protein accumulation and release from barley aleurone layers is presented for the important enzymes in starch degradation: α-amylase and limit dextrinase (LD). Proteins were visualized by immunoblotting in aleurone layers and culture supernatants from dissected aleurone layers incubated up to 72 h with either gibberellic acid (GA), abscisic acid (ABA) or salicylic acid (SA). The results show that α-amylase is secreted from aleurone layer treated with GA soon after synthesis but the release of LD to culture supernatants was significantly delayed and coincided with a general loss of proteins from aleurone layers. Release of LD was found to differ from that of amylase and was suggested to depend on programmed cell death (PCD). Despite detection of intracellular amylase in untreated aleurone layers or aleurone layers treated with ABA or SA, α-amylase was not released from these samples. Nevertheless, the release of α-amylase was observed from aleurone layers treated with GA+ABA or GA+SA.