Control of protein synthesis in barley aleurone layers by the plant hormones gibberellic acid and abscisic acid

Abstract

The patterns of protein synthesis in barley aleurone layers treated with gibberellic acid (GA 3) and abscisic acid (ABA) are compared with the patterns observed in wheat germ in vitro translation assays directed by RNA isolated from similarly treated layers. When used alone, GA 3 and ABA both induce the formation of new translatable mRNAs and cause new proteins to be synthesized. The effects of GA 3 are more dramatic than those of ABA. In GA 3-treated tissues, overall protein synthesis is redirected to produce large quantities of α-amylase and a few other GA 3-induced proteins, while other protein synthesis is reduced or stopped. Large amounts of new translatable mRNA for α-amylase are also induced such that the dominant in vitro translation product is α-amylase. These changes are blocked by the simultaneous addition of ABA to the tissue. In GA 3 plus ABA-treated layers, few changes in protein synthesis in vivo are observed when compared to protein synthesis in untreated tissue, although the induction of mRNA for α-amylase and the other GA 3-induced mRNAs does occur. This indicates that ABA does not interfere with GA 3 induction of translatable mRNAs but prevents the translation of these mRNAs in vivo. Thus ABA and potentially GA 3 regulate the translation of proteins in vivo in barley aleurone layers.