Figure 1.

A 1,003-bp region of the AtGA20ox2 promoter is regulated by the DELLA-GAF1 complex and responds to GA. A, Schematic representation of the reporter and effector. A 1,003-bp fragment of the AtGA20ox2 promoter was fused to the LUC gene. The effector plasmid expressed the full-length GAF1 or RGAΔ17 under the control of the CaMV 35S promoter with a viral translation enhancer (Ω). B, Transactivation assay of GAF1 and RGAΔ17. The effector, reporter, and internal control constructs were cobombarded into Arabidopsis leaves. The transfected leaves were incubated for 20 h, and then, LUC and rLUC activities were measured. The results are shown as LUC/rLUC activity. Error bars indicate sd (n = 3). C, Fluorometric GUS assay for GA negative feedback in transgenic Arabidopsis plants carrying the 1,003-bp AtGA20ox2 promoter::GUS construct. Gray and black bars represent the GUS activities of plants treated for 1 week with GA₃ and uniconazole (Uni), respectively. The striped bar represents the GUS activity of untreated control plants, which was arbitrarily set to 1. The mean activities of five independent transgenic lines for each construct are shown. Error bars indicate sd.