Figure 1.

The fbr12 mutant shows an FB₁-resistant phenotype and reduced PR gene expression. A, Two-week-old seedlings of wild type (Ws) and fbr12 germinated and grown in Murashige and Skoog medium in the absence or presence of 0.8 μm FB₁. Bar = 5 mm. B, Cell death induced by FB₁ in wild-type and fbr12 plants. Three-week-old seedlings were treated with dimethyl sulfoxide (DMSO; 0.05%; control) or 2 μm FB₁ for 24 h. Leaves were collected and stained with Trypan blue. Black staining represents dead or dying cells. C, Nuclear DNA fragmentation induced by FB₁ in wild type and fbr12. Protoplasts prepared from wild-type and fbr12 leaves were treated with DMSO (0.002%; control) or 50 nm FB₁ for 12 h and then analyzed by TUNEL staining as described in “Materials and Methods.” TUNEL-positive cells were counted under a fluorescent microscope (n > 1,000 in each experiment). Data presented were mean values of three independent experiments. Bars represent ses. D, FB₁-induced expression of PR1 and PR5 genes. Total RNA was prepared from 3-week-old seedlings treated with 3 μm FB₁ for various times as indicated and used for northern-blot analysis. Each lane contains 15 μg of RNA. The blot was hybridized with a full-length PR1 or PR5 cDNA probe, respectively.