Fig. 4.

Functional assay for auxin activity and auxin transport inhibition. Arabidopsis DR5::GUS seedlings were grown in the absence of chemicals; transferred to MS media containing 0.02% DMSO or chemicals 5403629 (3.3 μM), 5271050 (3.7 μM), 5850247 (35 μM), or 6220480 (30 μM); then stained for GUS activity 5 h later. (A) IAA and chemical 5403629 displayed intense staining, indicating DR5::GUS induction, whereas staining of 5271050-, 5850247-, and 6220480-treated seedlings were similar to the control (DMSO), indicating only basal induction of DR5::GUS. (B) Seedlings were pretreated with chemicals, 0.2% DMSO, or 100 μM TIBA for 14 h as in A; however, an agar block containing IAA was placed at the root tip (+IAA samples), and seedlings were stained for GUS activity 5 h later. (C) Test for auxin responsiveness. Seedlings were pretreated with chemicals and then incubated in a 1-μM IAA solution. (Bars, 0.2 mm.)