关键词: microtubule array, nematic order, zippering, microtubule growth

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 (N_I phase) with extremely long microtubules will be gapped by another nematic phase which consists of relative short microtubules (N_Ⅱ phase). The N_Ⅱ 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.

Key words: microtubule array, nematic order, zippering, microtubule growth