Figure 1.

Arabidopsis eto1-3 mutant plants display enhanced constitutive tolerance to freezing temperatures. (A) Levels of ET, as determined by gas chromatography, in 3-week-old Col-0 (WT) and eto1-3 plants grown on soil under long day conditions at 20°C. Data are expressed as means of 3 independent experiments with 5 plants each. Bars indicate ±SD. Asterisks indicate significant differences (P < 0.05) with WT plants. (B) Freezing tolerance of 2-week-old Col-0 (WT) and eto1-3 plants grown on soil under long day conditions at 20°C and then exposed 6 hours to the indicated freezing temperatures. Freezing tolerance was estimated as the percentage of plants surviving each specific temperature after 7 days of recovery under control conditions. Data are expressed as means of 3 independent experiments with 50 plants each. Bars indicate ±SD. Asterisks indicate significant differences (P < 0.05) with WT plants. (C) Expression levels of CBF1, CBF2 and CBF3 genes, as determined by qPCR, in 2-week-old Col-0 (WT) and eto1-3 plants grown on soil under long day conditions at 20°C. Analyses were performed in triplicate with 3 independent RNA samples. Bars indicate ±SD. Asterisks indicate significant differences (P < 0.05) with WT plants. (D) Freezing tolerance of representative WT and eto1-3 plants 7 days after being exposed to −6°C for 6 hours (h).