Minisymposium 8: Cell division

Abs # 21001: Catastrophic collisions and zippering of microtubules together promote ordering of the cortical array

Presenter:	Dixit, Ram , rvd10@psu.edu
Authors	Dixit, Ram  (A)   Cyr, Richard  (A)
Affiliations:	(A): Penn State University

The ordered configurations of cortical microtubules are essential for normal plant morphogenesis, but how these microtubules self-organize is unclear. The dynamic behavior of individual cortical microtubules is stochastic and cannot fully account for the observed order. We have used cultured tobacco cells, expressing a DsRed-labeled microtubule marker, to identify microtubule interactions that could modify their individual stochastic behaviors, thereby leading to order. The stochastic properties of individual microtubules are altered when microtubules encounter one another: steep-angle collisions are characterized by a 7-fold shorter microtubule contact time compared to shallow-angle microtubule encounters, and steep-angle collisions are twice as likely to result in complete microtubule depolymerization. Hence, steep-angle collisions promote microtubule destabilization whereas shallow-angle encounters promote both microtubule stabilization and coalignment. We hypothesize that these simple rules for inter-microtubule relationships modify individual stochastic behaviors and facilitate self-organization by promoting parallelism-- a conclusion validated by a Monte Carlo modeling technique. The data also shows an orientation-dependent, biased change in individual microtubule dynamics as cells progress into prophase. This change favors the disassembly of discordant microtubules and correlates to the transition from a mixed-orientation interphase array to a transverse preprophase band, which predicts the cell division site.