Fig. 2. Infiltration of the recombinant PBZ1 protein causes cell death in tobacco leaves. Tobacco leaves were infiltrated on an abaxial side using a needless syringe and morphological observation was recorded at 72 h post application. (A) Doesdependent effect of PBZ1 protein on cell death. 1, 10 mM HEPES buffer (pH 7.0); 2, acetylated BSA (100 μg/ml); 3 through 6 are recombinant PBZ1 protein at the concentration of 10, 25, 50 and 100 μg/ml, respectively. (B) Cell death blocking experiment. 1, acetylated BSA (100 μg/mL); 2, PBZ1 antibody (10 μl); 3, PBZ1 protein (100 μg/ml); and 4, PBZ1 protein (100 μg/ml) plus PBZ1 antibody (10 μl). Numbers 1 and 2 serve as appropriate controls.