Figure 1.

FB1-Induced PCD in Arabidopsis Protoplasts.

(A) Time and dose dependency of FB1-induced cell death. Protoplasts were prepared from wild-type plants and incubated in the light with various concentrations of FB1 (open squares, 0 nM; filled circles, 0.7 nM; filled squares, 70 nM; and filled triangles, 7 μM). Samples were withdrawn at 4, 8, 19, and 25 hr after the addition of FB1, and surviving fractions were determined as described in Methods. For control protoplasts (0 nM FB1), methanol was added instead of the FB1 solution at the final concentration of 0.1%. The methanol did not affect protoplast viability (not shown). The largest standard error in this experiment was 0.05.

(B) Requirement of plant cell activities for FB1-induced cell death. Protoplasts isolated from wild-type plants were incubated in the light for 16 hr in the presence of 70 nM FB1 (+FB1) or various inhibitors (100 μM cordycepin [+CORD], 10 μM cycloheximide [+CHX], and 1 μM staurosporine [+ST]), alone or in combination. In experiments 1 to 5, methanol was added instead of FB1 or inhibitor solutions. The final concentrations of methanol were as follows: experiment 1, 0.101%; experiments 2 to 4, 0.001%; and experiment 5, 0.1%. Surviving fractions were determined as described above. Error bars indicate sd.