Fig. 5.

Auxin transport and auxin-responsive promoter assays in cipk25. (A) Comparison of acropetal (rootward) and basipetal (shootward) root auxin transport in 5 dpg Col-0, cipk25, and CIPK25OX seedlings in a root segment 2 mm below (in acopetal) or above (in basipetal) the site of [³H]IAA application. Data are presented as the percentage of auxin transport relative to Col-0. Error bars are ±SD, t-test (*P≤0.05) of three measurements of 15 seedlings each. (B) Auxin-mediated root growth rate retardation of Col-0 and cipk25 in response to 0.1 µM and 0.5 µM auxin treatments. Col-0 and cipk25 mutant seedlings grown on 1/2 MS medium were transferred at 4 dpg to IAA-free or IAA-containing medium, and grown for an additional 5 d. Relative root growth rate in the presence of external IAA is presented as a percentage of the growth rate (per day) of the same line in control conditions (without IAA). The error bars represent ±SD, t-test (*P≤0.05), with three replicates of 10 seedlings each. (C) Auxin-responsive promoter activity using DR₅::GUS in Col-0 and the cipk25 mutant. Seedlings at 5 dpg were treated with 5 µM and 10 µM IAA for 2 h and stained for GUS activity.