Induction of α-amylase isoenzymes by gibberellic acid in imbibed rice half-seeds

Abstract

Expression of α-amylase isozymes was studied in germinating intact rice seeds, in embryonated and embryo-less (aleurones) half seeds with or without gibberellic acid treatment. Since most of the available information on rice α-amylases was obtained from scutellar tissues, this report focuses on the aleurone isozymes. Their isoelectrofocusing pattern and immunoreactivity are essentially similar to those of scutellum isoenzymes. Changes in gene expression were studied at various levels including modification in enzyme activity, time course of changes in isoenzyme patterns, immunochemical evaluation of changes in protein content for specific isoenzymes and in vitro translation of mRNA. All these experiments lead to the same conclusion: that in rice aleurone α-amylase isozymes are induced by exogenous gibberellic acid in a similar way as in other studied cereals, although at a lower level. These observations complement previous reports made on the scutellum isoenzymes which indicated that the rice α-amylases in this tissue were insensitive to exogenous gibberellic acid.