Regulation of microtubule array in its self-organized dense active crowds**Project supported by the National Natural Science Foundation of China (Grant Nos. 11474155, 11774147, 11674236, and 11922506).

Abstract

Microtubule self-organization under mechanical and chemical regulations plays a central role in cytokinesis and cellular transportations. In plant-cells, the patterns or phases of cortical microtubules organizations are the direct indicators of cell-phases. The dense nematic pattern of cortical microtubule array relies on the regulation of single microtubule dynamics with mechanical coupling to steric interaction among the self-organized microtubule crowds. Building upon previous minimal models, we investigate the effective microtubule width, microtubule catastrophe rate, and zippering angle as factors that regulate the self-organization of the dense nematic phase. We find that by incorporating the effective microtubule width, the transition from isotropic to the highly ordered nematic phase (NI phase) with extremely long microtubules will be gapped by another nematic phase which consists of relative short microtubules (NII phase). The NII phase in the gap grows wider with the increase of the microtubule width. We further illustrate that in the dense phase, the collision-induced catastrophe rate and an optimal zippering angle play an important role in controlling the order–disorder transition, as a result of the coupling between the collision events and ordering. Our study shows that the transition to dense microtubule array requires the cross-talk between single microtubule growth and mechanical interactions among microtubules in the active crowds.