Figure 1.
Base substitution analysis of the 77-bp region of the rd29B promoter involved in ABA- and dehydration-responsive expression in transgenic tobacco. GUS activity before and after treatment was measured in 20 independent transformants for each construct and is shown as average values. MU, 4-methyl-umbelliferone. (A) Upper-strand sequences of the 77-bp fragment (wild type) and its mutated sequences (M1-M6). The monomer (x1) or tandemly repeated dimer (x2) of each 77-bp fragment containing different mutations was ligated to the −51 rd29B minimal TATA promoter-GUS construct, respectively. Dashes indicate the wild-type sequence. (B) Effect of base substitutions in the ABRE and MYB recognition sites for dehydration-responsive expression of the rd29B. Half of the leaf from T1 tobacco plant was used immediately for the assay of GUS activity (control), and the other half was dehydrated for 24 h (dry). (C) Effect of ABA treatment on the induction of the GUS reporter gene driven by the 77-bp fragment. T2 tobacco seedlings were used immediately for the assay of GUS activity (control), transferred from agar plates for hydroponic growth in water (H2O) or 100 μM ABA (ABA) solution, or dehydrated for 24 h (dry).