Fig. 1

Schematic illustrations of cortical microtubule (CMT) dynamics, their interactions, and the effect of the directional cue (DC). The blue and green spheres in (A–F) represent \(\:{\upalpha\:}\) and \(\:{\upbeta\:}\)-tubulins, respectively. The green and magenta oval-like fragments represent the growing and shrinking ends of the microtubule, respectively. The orange region is the DC zone. (A) Microtubule (MT) growth, when the CMT plus end grows at speed \(\:{v}^{+}\). (B) MT shrinkage, when the CMT plus end shrinks at speed \(\:{v}^{-}\) while the CMT minus end undergoes shrinkage at speed \(\:{v}^{tm}\). The rescue rate \(\:{r}_{r}\), which represents the rate of change from growth to shrinkage at the plus end, and the catastrophe rate \(\:{r}_{c}\), which represents the rate of change from shrinkage to growth at the plus end, are also shown. (C) CMT zippering, when one CMT interacts with another within 40° and changes its direction to align with the other. At this angle of interaction, zippering occurs at 100% frequency. (D) Induced CMT catastrophe, when one CMT interacting with another at an angle greater than 40° is induced to depolymerize. (E) CMT crossover, when two CMTs interact with each other at an angle greater than 40° and cross one another. The induced catastrophes (D) and crossovers (E) each occur with a probability of 50% when CMTs meet at an angle greater than 40°. (F) CMTs with a DC, which causes CMTs within the DC zone to change their direction to gradually align to a specific direction (circumferential in this study).