Mathematics Colloquia and Seminars

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Microtubule (MT) organization in most animal cell contexts depends largely on the presence of the centrosome which serves as an MT organizing center through its nucleation and stabilization functions. Interestingly, recent studies have suggested that more distributed pathways for MT organization, independent of the centrosome, may also play a significant role, for example in mitotic spindle formation and maintenance. In contrast with animal cells, plants have no centrosomes and rely entirely on other means to achieve MT organization. In this talk, I will describe the emergence of highly oriented arrays of MTs that are seen during elongation of plant cells. By formulating a system of integro-differential equations for length- and angle-dependent populations of MTs, some of the current hypotheses for pattern formation, specifically MT-MT contact-induced catastrophe and zippering, can be tested. The analysis partially confirms published model simulations but more importantly uncovers a complicated interaction between the proposed mechanisms. In particular, MT zippering on its own is incapable of driving MT orientation but contact-induced catastrophe does promote orientation. Furthermore, when both mechanisms are included, zippering enhances the orienting influence of contact-induced catastrophe. In addition, scaling arguments allow predictions to be made regarding mutant phenotypes with modified dynamic instability parameters. This is ongoing work in collaboration with Jun Allard (PhD candidate) and the Wasteneys Lab (UBC Botany).