Online Supplementary Material Canalization without flux sensors: a traveling-wave hypothesis

Figure S1. Stability of channels formed according to the traveling-wave channeling model. To form stable auxin channels, cells must remain polarized for some time after the auxin wave has moved on. If we increase the PIN1 internalization rate ( k2 = 1e-02, i.e. three orders of magnitudes faster than the default value), auxin waves appear, but they do not form continuous auxin channels. This phenomenon resembles an observation by Enrico Scarpella and coworkers [1], who demonstrated that although PIN1 expression domains form normally in the van-3 discontinuous vein mutant, they break up into disconnected patches later on. VAN-3 is auxin-induced and is possibly self-regulated [2], suggesting it might function to sustain PIN1 exocytosis after th