Figure 6.

siPD B8 and siPD U9 plants have reduced cell death in response to avirulent bacteria. A and B, Comparative analysis of responses triggered by avirulent pathogens (5 × 10⁶ cfu mL⁻¹) in wild-type (wt) and ProDH-silenced (siPD B8 and siPD U9) plants. ProDH1 and ProDH2 transcript abundance (A) and ProDH levels (B) are quantified in untreated and Pst-AvrRpm1-treated leaves at 6 and 24 hpi, as described in Figure 1, C and D. One representative from three independent experiments is shown, and each experiment included three plants and four leaves from different plants per time point. C, Identification of nonviable cells in Pst-AvrRpm1- or Pst-AvrRps4-challenged leaves isolated at 24 hpi by SYTOX Green staining and laser-scanning confocal microscopy (Truernit and Haseloff, 2008). Green signals indicate probe fluorescence, and red signals indicate chlorophyll autofluorescence. Images are representative of 18 total images. Bar = 400 μm. D, Quantification of stained nucleus per leaf area from the images described in C using ImageJ software (W. Rasband, National Institutes of Health). Values represent means ± se of quantification of 18 images from three biologically independent infection experiments, each one containing three plants per genotype. Significant differences between wild-type and transgenic plants are indicated (* P < 0.01, t test). E, Pst-AvrRpm1-treated leaves were excised at 48 hpi to be stained with trypan blue (top row) or analyzed at 72 hpi for macroscopic HR features (bottom row). One representative from 20 leaves is shown per genotype (three independent infection experiments and four plants each).