Figure 5.

HBI1 overexpression increases BR responses. A, HBI1 expression kinetics after epiBL treatment monitored by RT-qPCR. Two-week-old Col-0 seedlings were treated with 1 µm epiBL for the indicated times. Transcript levels were normalized to U-box transcript levels and relative to time zero. Results are averages ± 2× se (n = 3). One-way ANOVA/Holm-Sidak: ***P < 0.001. B, Fresh weight of 2-week-old seedlings grown in liquid MS medium. Results are averages ± 2× se across four independent experiments. Two-way ANOVA/Holm-Sidak: ^a≠bP < 0.003. C, Hypocotyl lengths of 6-d-old seedlings grown under long-day conditions on one-half-strength MS medium supplemented with a concentration gradient of epiBL. Results are averages ± 2× se (n = 11–23). One-way ANOVA/Holm-Sidak: ***P < 0.00. D, Hypocotyl lengths of 6-d-old seedlings grown in the dark on one-half-strength MS medium supplemented with a concentration gradient of BRZ. Results are averages ± 2× se (n = 17–21). One-way ANOVA/Dunnett: ***P < 0.001. E, Stem-branch junction bending of long-day-grown 5-week-old plants. Results are averages ± 2× se (n = 20). One-way ANOVA/Holm-Sidak: ***P < 0.001. F, Steady-state expression of the BR marker gene EXP8 in 2-week-old seedlings measured by RT-qPCR. The transcript levels were normalized to U-box gene expression and relative to Col-0. Results are averages ± 2× se (n = 3). One-way ANOVA/Holm-Sidak: ***P < 0.00. G, Phenotypes of 4-week-old short-day-grown (left) and 5-week-old long-day-grown (right) plants. H, Hypocotyl lengths of 6-d-old seedlings grown under long-day conditions on one-half-strength MS medium supplemented with a concentration gradient of epiBL. Results are averages ± 2× se (n = 12–23). All genotypes are different from each other: P < 0.001. All experiments were repeated at least three times with similar results.