Expression of conserved message of poly(A) polymerase through hormonal control in wheat aleurone layers

Abstract

Poly(A) polymerase has been reported in both animal and plant cells [ 11. Increased polyadenylation of a messenger fraction has been reported for fertilized sea urchin eggs [2] and GAa-treated barley aleurone layers [3]. However, the real significance of polyadenylation is somewhat cryptic [4,5]. The hormonal control of poly(A) polymerase was first reported in [6]. Essentially, we observed a 2-3-fold stimulation of poly(A) polymerase activity in GAytreated embryoless half seeds of wheat. We found that this increased enzyme activity is not due to any structural modification of a preformed enzyme. Inhibitor studies indicated the necessity of de novo protein synthesis for the GAatriggered enzyme activity [6]. However, this approach did not tell us whether the hormone regulates the enzyme activity at the transcriptional, posttranscriptional or translational level. Here, we provide evidence for the translation of a GAsstimulated poly(A) polymerase from conserved message in wheat aleurone layers. The hormone-stimulated enzyme activity was completely inhibited by abscisic acid (ABA). Clearly, the hormones control poly(A) polymerase activity by operating at the post-transcriptional level. We propose that GA3 activates the conserved message of poly(A) polymerase, while ABA inhibits this process.