Gibberellic Acid and Rna Synthesis in Barley Aleurone Layers: Metabolism of rRNA and tRNA and of RNA Containing Polyadenylic Acid Sequences

Abstract

RNA containing polyadenylic acid sequences [poly(A)-RNA] was detected in and isolated from barley aleurone layers. Gibberellic acid (GA₃) stimulated the synthesis of this RNA by about 70% over a 16-h period during which amylase induction occurred. The poly(A)-RNA was polydisperse on polyacrylamide gels and the effect of GA₃ was to enhance synthesis of poly(A)-RNA species with a wide range of molecular weights.

GA₃ had no major effects on the synthesis of rRNA, 5 S RNA and tRNA species, and since it also had no effect on levels of total RNA in aleurone, it probably had no effect on RNA breakdown. Furthermore, rRNA synthesis could be essentially stopped with 5-fluorouracil with no effect on amylase synthesis, indicating that synthesis of new ribosomes was unnecessary for normal amylase induction.

These results indicate that for amylase synthesis to occur in response to GA₃, regulation of synthesis of mRNA but not that of the major species would appear to be necessary.