Figure 3. The expression of fabB in X. oryzae pv. oryzicola is negatively by hrpX and hrpG in rice suspension cells.

(A) Schematic map of the promoter region containing PIP-box and -10 box-like motif of fabB fused with a promoterless gusA gene. * stands for base substitutions. The constructs are listed on the right. (B) Expression analysis of fbaB by real-time quantitative RT-PCR. RNAs were isolated from cultures of the wild-type RS105, the hrpG deletion mutant RΔhrpG and the hrpX deletion mutant RΔhrpX strains which were grown in NB medium and rice suspension cells for 16 h, respectively. The relative mRNAs level of fbaB was calculated with respect to the level of the corresponding transcript in the wild-type RS105. (C) Effects of the mutated PIP-box on gusA transcript. The gusA transcript level by the wild-type PIP-box promoter (a) and three base-substituted PIP-box promoter (b, c, d) in the wild-type RS105, the hrpX mutant RΔhrpX and the hrpG mutant RΔhrpX were investigated, respectively. All the reporter strains above were cultured in rice suspension cells for 16 h and gusA transcript levels were then determined by real-time PCR. The transcript of gusA in the wild-type was taken as one unit. Data are the mean ± SD of triplicate measurements from a representative experiment; and similar results were obtained in two other independent experiments. The asterisks in each horizontal data column indicate significant differences at P = 0.01 by t test.