Figure 2.

The mekk1 dwarf phenotype is caused by constitutive expression of stress response genes. A, Condition tree comparing the gene expression profile of mekk1-1 plants with various stress-treated Arabidopsis samples from a public database. Dark red indicates highly up-regulated genes, dark blue indicates highly down-regulated genes, and yellow indicates genes with little change in expression. B, RT-PCR of eight genes showing a high level of up-regulation in mekk1-1 plants in the microarray experiment. Three independent biological replicates were tested (Rep 1–Rep 3). 32°, Plants grown for 3 weeks at 32°C. 24°, Plants grown at 32°C for 3 weeks followed by 24 h at 24°C. Fold change indicates the relative expression level of each gene in mekk1-1 compared to wild-type Col-0 grown in the same conditions. C, Eleven-day-old seedlings stained for callose deposition and visualized using UV epifluorescence microscopy. No callose-inducing treatment was given to the seedlings. D, Two-week-old plants grown at 27°C. mekk1-2 + nahG is a homozygous mekk1-2 plant stably transformed with the nahG transgene. White arrows indicate representative primary leaves for comparison. One leaf is missing from the mekk1-2 + nahG plant, because it was harvested for genotyping. Bars = 0.5 cm.