Figures & data
Figure 1 A working model for the auxin regulation of the pavement cell interdigitation pattern. (A) Auxin is proposed to modulate PC interdigitation through activating mutually exclusive ROP2 and ROP6 pathways, which are localized to the lobing and indenting side and promote lobe protrusion and neck indentation, respectively. ROP2 promotes PIN1 localization to the apex of lobe that further activates an auxin-ROP2-PIN1-auxin positive feedback loop. (B) Auxin activates ROP2 and ROP6 with different kinetics. ROP2 and ROP6 have similar response when the auxin level is low as 1 nM, but ROP6 activation has higher saturation level at 1 µM while ROP2 activation saturated at around 100 nM.
Figure 2 ROP GTPase regulation of PIN protein localization in different cells. In leaf PCs, ROP2 promotes PIN1 PM localization at the lobe tip and further initiates a positive feedback at this region. The mutual inhibition between ROP2 and ROP6 help to restrict the localization of PIN1 at the lobe site. In root vascular cells, ROP2 or ROP2-like pathway is speculated to participate in a positive feedback at the basal site that continuously promotes PIN1 localization and auxin flow. In other sides, a ROP6 or ROP6-like pathway is speculated to inhibit the ROP2 pathway that further restricts PIN1 localization to the basal site.
