Figure 7.

PISA inhibits auxin distribution and root gravitropism. A, Effect of PISA on auxin asymmetric distribution. Four-d–old DR5::GFP seedlings were transferred to 20-μm PISA and control medium for 1 h. After 1 h, seedlings were gravistimulated for 4 h and imaged. PISA pretreatment abolished auxin asymmetric distribution and seedlings did not respond to gravity stimuli. B, Quantitative evaluation of (A), showing a mean ratio of the signal intensity of the upper-/lower-half of the root. (*P < 0.01). C, Effect of PISA on root gravitropic response. Five-d–old wild-type seedlings were placed on vertical GM agar plates containing PISA and then cultured for 3 h in the dark. The plates were further incubated for 16 h after rotating plates at 135° angle against vertical direction. The arrows indicate the vector of gravity before (1) and after (2) the initiation of gravistimulation. The angles were grouped into 30° classes and plotted as circular histograms.