Regulation of Aux/IAA gene expression by DELLA proteins. A, Expression of IAA5, IAA6, and IAA19 determined by reverse transcription quantitative PCR in 3-d-old dark-grown HS::gai-1D seedlings after a 30-min heat shock at 37°C. Values at each time point are relative to the expression of each gene in seedlings not subject to heat shock. Error bars represent sem (n = 3 biological replicates). B, Expression of IAA5, IAA6, and IAA19 determined by reverse transcription quantitative PCR in 3-d-old dark-grown seedlings expressing a fusion between gai-1D and the glucocorticoid receptor (GR) under the control of the GAI promoter. Three-day-old dark-grown seedlings were transferred into flasks and incubated with soft shaking for 6 h with a mock solution or with 10 μm dexamethasone (DEX) to allow gai-1D:GR moving to the nucleus and regulate target genes. Alternatively, seedlings were also incubated with 10 μm cycloheximide (CHX) to prevent de novo protein synthesis during mock or DEX treatments. Values are relative to the expression of each gene in mock-treated seedlings. Error bars represent sem (n = 3 biological replicates).