Modulation by abscisic acid and S-2-aminoethyl-L-cysteine of α-amylase mRNA in barley aleurone cells.

The changes in the levels of α-amylase mRNA is barley aleurone layers in response to addition of plant growth regulators have been studied using a cloned α-amylase cDNA as the hybridization probe. An increase in gibberellic acid (GA) concentration in the incubation medium from 10(-9) M to 10(-6) M results in a progressive increase in α-amylase mRNA concentration in the aleurone cells. Detectable levels of α-amylase mRNA appear in the aleurone cells as early as 1 h after addition of GA. The concentration of this mRNA increases for several hours and then declines rapidly. Abscisic acid (ABA) and the amino acid analog S-2-aminoethyl-L-cysteine (AEC) suppress the GA-mediated induction of α-amylase. These compounds appear to affect the level of α-amylase mRNA in aleurone cells as measured byin vitro translation assays and by analysis of RNA blots with α-amylase cDNA probes. It is concluded that the regulation of α-amylase gene expression by ABA is at the level of transcription. Further, a protein factor appears to be required in addition to GA for transcription of α-amylase genes.