Figure 7.

Schematic model for developmental shaping of polar auxin flow during leaf thermonasty. Thermo-activated PIF4 triggers auxin production in the leaf blade. Auxin is then transported to the petiole, where it is distributed toward the epidermis via PIN3. PIF4 also activates PID transcription in the petiole. The leaf polarity determinant AS1 directs PID transcription to occur predominantly in the abaxial petiole region. The PID-mediated PIN3 polarization to the outer membrane of abaxial petiole cells determines the direction of leaf bending. Blue arrows marks the paths of auxin flow.