Figure 1.

Arabidopsis cax1 lines are anoxia tolerant. A, Enhanced anoxia tolerance in cax1-1 and cax1-2 compared to Col-0 and cax3. Twenty-one-day-old plants (nine-rosette leaf stage) were placed in a GasPack Anaerobic system. After 8 h, plants were returned to normoxia conditions and photographed after 4 days. Photographs represent more than 15 biological replicates in each condition. B, Post anoxia cax1 exhibited less chlorophyll loss than Col-0 and cax3. Plants belonging to nine-rosette leaf stage were treated as described in Figure 1B and aerial portions of the plants were sampled 24 and 48 h after returning to normoxia conditions. Plants sampled prior to the anoxic conditions were used as controls. All results are means ± sem, n = 3 and error bars indicate standard error of the mean. Individual data points represented with a gray circle and asterisk indicate significant difference from the pre-treatment conditions at P =0.01, as calculated from Student’s t test in Excel. C, Expressing CAX1 under the CAX1 promoter (pcax1::CAX1) in cax1-1 caused sensitivity to anoxia. Assay conditions similar to those described in (B). The data are a representative of 14 different transgenic lines analyzed. D, Chlorophyll loss following anoxia in two cax1-1 lines expressing CAX1 under its native promoter (pcax1::CAX1#1, pcax1::CAX1#2). The data are a representative of 14 different transgenic lines analyzed. Individual data values from three biological replicates are represented with a grey circle and error bars indicate standard error of the mean. Student’s t test was used to calculate the statistical significance and an asterisk indicates a P ≤0.001. The increase in CAX1 expression in the transgenic lines has been confirmed by RT–qPCR as shown in Supplemental Figure S1E. Assay conditions similar to those described in (B) and (C).