| Summary: | 碩士 === 國立臺灣大學 === 植物科學研究所 === 92 === In this study, I analyzed the activity of maize (-amylase promoter via particle bombardment-transient expression assay using uidA as a reporter gene. Aleurone layers isolated from 3-day-old seedlings, 4-day-old developing and 8-day-old fully expanded primary leaves, and mature foliage leaves were used as experiment tissues. The full-length (1.6 kb) promoter can express in aleurone layers and developing primary leaves, but the activity was much reduced in the fully expanded leaves. Full-length promoter in aleurone layers and developing leaves showed no significant increase in response to GA treatment. However, upon treatment with ABA, the activity dropped to 10% of the control level. In the presence of both GA and ABA, the activity was restored to the level of GA-treatment alone. Application of sugar and GA to mature leaves enhanced the promoter activity by 4- and 10-fold, respectively. There are three amybox 1, two amybox 2 and one ABRE cis-elements in the maize (-amylase promoter. Deletion of amybox 1 or amybox 2 caused a reduction in promoter activity by 40% and a decrease in sensitivity to ABA treatment. Deletion of amybox1 eliminated the antagonistic efficacy of GA against to ABA inhibition. Deletion of ABRE showed no influence on the promoter activity, but it did interfere with the ABA effect. There is an age gradient from base to tip in a fully expanded blade of a 22-day-old plant, and the activity of ��-amylase gene decreased along with age. Exogenous GA application can restore the activity of the promoter only in the basal half of the blade. Deletion of ABRE from the promoter stimulated the activity 3 times higher than the intact promoter in mature leaves, although the truncated promoter was still sensitive to ABA inhibition. These results suggested that ABA is at least partially involved in the down regulation of ��-amylase gene expression during leaf maturation.
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