Figure 6.

Enhanced susceptibility of CaRING1-silenced pepper plants to infection with the virulent Xcv strain Ds1 and the avirulent Xcv strain Bv5-4a. A, Disease symptoms developed on empty vector control (TRV:00) or CaRING1-silenced (TRV:CaRING1) pepper leaves 6 and 3 d after inoculation with the virulent (Ds1; compatible) and avirulent (Bv5-4a; incompatible) strains, respectively. Highlighted areas of leaves show areas inoculated with the bacterial concentrations indicated. Infected leaves with UV-fluorescing phenolic compounds associated with susceptibility to infection and HR cell death are shown in the right panels. B, Growth of the virulent Xcv strain Ds1 and avirulent Xcv strain Bv5-4a in empty vector control (TRV:00) or CaRING1-silenced (TRV:CaRING1) pepper leaves at 0 or 3 d after inoculation (5 × 10⁴ cfu mL⁻¹). Data represent means ± sd from three independent experiments. Asterisks indicate significant differences between empty vector control and CaRING1 gene-silenced pepper plants as determined by Student’s t test (P < 0.05). C, Reduced H₂O₂ production and cell death in CaRING1-silenced leaves infected with the avirulent Xcv strain Bv5-4a (10⁷ cfu mL⁻¹). Xcv-infected leaves were harvested and stained with 3,3-diaminobenzidine (DAB) and trypan blue at 12 and 24 h after inoculation, respectively. Bars = 500 μm. D, Production of H₂O₂ in leaf discs from empty vector control (TRV:00) and CaRING1-silenced (TRV:CaRING1) pepper leaves at different time points after inoculation with 10⁷ cfu mL⁻¹ of the avirulent Xcv strain Bv5-4a. Data represent means ± sd from three independent experiments. Asterisks indicate significant differences between empty vector control and CaRING1-silenced pepper plants as determined by Student’s t test (P < 0.05). E, Cell death was monitored by electrolyte leakage (conductivity) from empty vector control (TRV:00) and CaRING1-silenced (TRV:CaRING1) pepper leaves challenged with the avirulent Xcv strain. Data represent means ± sd from three independent experiments. Asterisks indicate significant differences between empty vector control and CaRING1-silenced pepper plants as determined by Student’s t test (P < 0.05).