Figure 4.

The protein kinase and auxin transport inhibitor, quercetin, reverts PID-mediated ABCB1 inhibition in yeast. (A) Reduction of auxin (IAA) and BA retention (export) in the presence or absence of inhibitors (C, solvent control) is presented as relative export of initial export where ABCB1 solvent control was set to 100% (mean±s.e.; n=4–10). Significant differences (unpaired t-test with Welch’s correction, P<0.05) to −PID solvent control (one asterisk) or +PID solvent control (two asterisks) are indicated. Note that chelerythrine (chel; each 1 μM) unlike quercetin (quer) and staurosporine (stau) led to strong activation of vector control (backround) auxin efflux in the presence and absence of PID (not shown) requiring a relative presentation of activities. (B, C) Drug treatment (each 1 μM) does not significantly alter location (B) and expression (C) of ABCB1-YFP as revealed by confocal microscopy and western analysis. About 20 μg of each protein was subjected to PAGE and western analysis using anti-GFP and plasma-membrane marker, anti-PMA1 (H⁺-ATPase). ABCB1-YFP localizes primarily to raft-like structures and the plasma membrane (see Supplementary Figure S2; Bailly et al, 2008). Bar, 2 μm.