Gibberellic Acid Activates Chromatin-bound DNA-dependent RNA Polymerase in Wounded Potato Tuber Tissue

Abstract

Chromatin-bound DNA-dependent RNA polymerases react upon wounding of white potato tuber tissues with an increase in activity, which is additionally enhanced to 300% in the presence of0.1 micromolar gibberellic acid (GA3). 2,4-Dichlorophenoxyacetic acid is only weakly effective and indoleacetic acid not at aLL Wounding and treatment with GA3 affect template availability of chromatin only slightly. The hormone has no effect on chromatin-bound RNA polymerases, if added in vito. Wounding of plant storage tissues such as potato tuber tissue induces a wide spectrum of biochemical changes, such as de novo synthesis of various kinds of RNA and the formation of polyribosomes which are engaged in protein synthesis (12-14, 16, 25). A wounding-induced increase in nucleolar size (13,22) and an enhanced activity of chromatin-bound RNA polymerases (4, 15, 16) or increase in template availability (4) are all characteristic features of injured tissues.It is well known that plant hormones may be involved in the regulation of transcription or translation processes (17,22, 24,27). The hormone-induced changes in the rate of synthesis of new RNA species (16,21, 25, 26) may reflect the activation of previously inactive genes or the activation or synthesis of RNA polymerases (2,6,7,22). Both possibilities may well be realized. So, GA3 induces the RNA synthesis in isolated pea nuclei (11). The first effect of the hormone seems to be on the enhancement of template availability and afterward on RNA polymerase activity (10). An increased template availability of chromatin from hormone- treated tissues (4, 5) could not be confirmed by others (8,20), who demonstrated a significant increment of chromatin-bound RNA polymerase as an early effect. Here, we report that wound healing of white potato tuber tissue in the presence of GA3 significantly enhances the activity of chromatin-bound RNA polymerase I and less of RNA polymerase II, whereas the template availability of chromatin is only slightly increased. MATERIALS AND METHODSThe plant material and its treatment have been described in detail in a preceding paper (25).Isolation of Chromatin. Chromatin was isolated according to a modified method of Huang and Bonner (9). The tissue (250 g

Auxin-induced changes in chromosomal protein phosphorylation in wounded potato tuber parenchyma

“…Nearest-neighbour frequency analysis of the RNA from resting and wounded tissues revealed that the quality of the RNA and hence the quality of transcription change after an injury [11]. The mechanism of this wound-induced activation of RNA synthesis is not clear, although hormones interfere with this process [ 11,22,30,31]. Gibberellic acid (GA3) if exogenously supplied to wounded tissues, enhances transcription over untreated controls.…”

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

“…This activation process leads to a conditioned cell The present results clearly show that the synthesis of different RNA species and consequently the polyribosome formation are under control of GA3. The hormone is recognized by wounded tissue in a time-specific way, the signal is somehow transferred to the genome, and triggers the activation of gene transcription (39).…”