Effect of the interaction between CAT3 and HL2b on cell death of Arabidopsis Col-0 protoplasts. A, Percentage of cell death for transfected Col-0 protoplasts at 20 h after transfection with GFP (control, 10 μg), HL2b (5 μg) + GFP (5 μg), GFP (5 μg) + CAT3 (5 μg), or HL2b (5 μg) + CAT3 (5 μg). Cells that were stained by Evans blue were scored as dead. Data are percentages of cell death after the control percentage was subtracted from the background. Error bars represent se of the means of three replicates. Differences in the means were evaluated with a t test; ** significant at the 1% level. B, Catalase activities in Col-0 protoplasts transfected with GFP (control), HL2b + GFP, GFP + CAT3, or HL2b + CAT3 at 20 h after transfection. Activity was measured spectrophotometrically. Error bars represent se of the means of three replicates. Differences in means among groups were evaluated by t test; * significant at the 5% level.