Figure 4.

chs2 constitutively activates defense responses to cold. Wild-type Col and chs2 plants were grown at 22°C for 3 weeks and then treated at 4°C for 6 d. For A, B, and E, 20 plants were tested for each genotype. Images are of representative plants from one of three independent experiments. A, H₂O₂ accumulation in chs2 plants stained by DAB. Bar = 20 μm. B, Cold-induced cell death in chs2 plants. Detached leaves were stained with trypan blue. Bar = 100 μm. Images are of representative plants. C, Expression of PR1 and PR2 in wild-type and chs2 plants by real-time RT-PCR. The data represent means of three replicates ± sd. Similar results were observed in three independent experiments. D, GUS analysis of PR1 in chs2 plants. PR1:GUS transgenic plants were crossed with chs2 plants. The F2 homozygous lines were used for GUS staining analysis. Images are of representative plants. E, SA accumulation in chs2 under cold conditions. Three-week-old 22°C-grown plants were treated at 4°C for 6 d. The data represent means of three replicates ± sd. Similar results were observed in three independent experiments. FW, Fresh weight.