Response of barley aleurone layers to abscisic Acid.

Cordycepin, an inhibitor of RNA synthesis in barley (Hordeum vulgare L.) aleurone cells, does not inhibit the gibberellic acid-enhanced alpha-amylase (EC 3.2.1.1.) synthesis in barley aleurone layers if it is added 12 hours or more after the addition of the hormone. However, the accumulation of alpha-amylase activity after 12 hours of gibberellic acid can be decreased by abscisic acid. The accumulation of alpha-amylase activity is sustained or quickly restored when cordycepin is added simultaneously or some time after abscisic acid, indicating that the response of aleurone layers to abscisic acid depends on the continuous synthesis of a short lived RNA. By analysis of the newly synthesized proteins by gel electrophoresis with sodium dodecylsulfate, we observed that the synthesis of alpha-amylase is decreased in the presence of abscisic acid while the synthesis of most of the other proteins remains unchanged. From the rate of resumption of alpha-amylase production in the presence of cordycepin and abscisic acid, it appears that abscisic acid does not have a measurable effect on the stability of alpha-amylase mRNA.