Figure 1.
Evaluation of PISA for an auxin-like effect in the SCFTIR1/AFB pathway. A, The structures of auxins and PISA. B, Effects of PISA on auxin-deficient root phenotypes. Arabidopsis plants were cultured for 5 d on vertical agar plate containing chemicals with or without auxin biosynthesis inhibitors yucasin DF and L-kynurenine (Kyn). The values in parentheses represent the concentration of chemicals (micromolar). Bar = 5 mm. C, Effects of alkyloxy-PAA on auxin-responsive DR5::GUS expression. Five-d–old DR5::GUS seedlings were incubated with chemicals for 6 h. Methoxy (C1) to pentoxy (C5) PAA derivatives including mPISA and PISA were assessed at 50 μm. D, Quantitative analysis of GUS enzyme activity in the DR5::GUS line treated with IAA and PISA. Values are the means ± sd (n = 9). E, DII-VENUS seedlings were incubated with 10-μm yucasin DF for 3 h and then washed with medium. The seedling was incubated with PISA and IAA for another 60 min. Bar = 500 μm. F, SPR analysis of the auxin-induced interaction between TIR1 and IAA7 degron peptide. The sensorgram shows the effect of 50-μm IAA (green) and 50-μm PISA (blue) on TIR1-DII peptide association and dissociation. The bars show the relative response of PISA to IAA (100%).