Preferential Stimulation of the Plant mRNA Synthesis by Gibberellic Acid

Abstract

1. Treatment of the etiolated maize seedlings with the plant hormone, gibberellic acid results in a significant enhancement of heavy polyribosome formation.2. This is accompanied by highly increased incorporation of the labelled RNA precursors into RNA engaged in the polyribosomal complex, as well as by an increased rate of protein synthesis in vivo.3. Determination of the specific radioactivity of particular RNA classes isolated from polyribosomes reveals that gibberellic acid stimulates mostly the synthesis of the rapidly labelled, nonribosomal RNA fraction.4. A considerable amount of this rapidly labelled RNA fraction, whose synthesis is preferentially stimulated by exogenous gibberellic acid contains poly(A) sequences, as shown by affinity chromatography on oligo(dT)-cellulose, indicating that phytohormone causes an increased transcription of mRNA in etiolated maize seedlings.5. When [3H]adenosine served as the RNA precursor it was found that the ratio between the heteropolymeric and polyadenylic parts of the poly(A)-RNA chain markedly changed under gibberellin treatment, suggesting that, in addition to an increased rate of mRNA synthesis, the plant hormone also affects the process of post-transcriptional polyadenylation of the newly made mRNA precursors. Possible extension of the polyadenylate segment in the presence of gibberellin may account for a longer functional half-life of the mRNA synthesized in plants treated with the phytohormone, and may explain significantly enhanced heavy polyribosome formation, as well as a higher efficiency of protein synthesis in plants treated with gibberellic acid.

Enhancement of Polyribosome Formation and RNA Synthesis of Gibberellic Acid in Wounded Potato Tuber Tissue

“…All other concentrations were less effective (10 ,UM, ,UM, 10 nm, and 1 nm GA3 each stimulates only about 20 to 50%o that of 0.1 UM). This is in agreement with many reports from other plant systems (12,38,40,41).…”

“…It has been shown in a variety ofplant systems that GA3 induces RNA synthesis (13,14,22,40,41), polyribosome formation (12,38), and increases in activity of various enzymes (35). We were interested in determining whether or not plant hormones are involved in the wounding phenomenon.…”

“…Although this "primary action" is not known yet, some authors suggest that it takes place at the membrane level (26,42). The time-dependent development of responsiveness of a given tissue toward GA3 evidently is a widespread phenomenon (12,35,38,40,41 first 2 h after wounding sugar beet root (37) and Jerusalem artichoke tuber tissue (5). Later on, radioactivity is progressively incorporated into rRNA, also (5,16,37).…”

Hormones in Seed Dormancy and Germination

“…The involvement of hormones in the control of processes that lead to protein biosynthesis has often been investigated (Teissere et al, 1973; 1975; Tarantowicz-Marek et at., Wasilewska and Kleczkowski, 1976). The synthesis of amylase in aleurone cells of germinating cereal grains is stimulated by GA Varner et al, 1965).…”