A Mechanism for Reorientation of Cortical Microtubule Arrays Driven by Microtubule Severing

Abstract

Light Turns the Array The organization of cortical microtubule arrays in higher plant cells is essential for organizing cell and tissue morphogenesis, but it is not clear how specific architectures are acquired and reconfigured in response to environmental cues. Lindeboom et al. ( 10.1126/science.1245533 , published online 7 November; see the Perspective by Roll-Mecak ) used live-cell imaging and genetic studies to show that the microtubule-severing protein, katanin, plays a crucial role in reorienting cortical arrays from transverse to longitudinal in Arabidopsis seedlings in response to blue light perception. Katanin localized to microtubule intersections where, stimulated by blue light receptors, it preferentially catalyzed the severing of the newer microtubule. The microtubule “plus” end created by severing were observed to grow preferentially, effectively building a new population of microtubules orthogonal to the initial array. The net effect of this process steers the growing seedling toward light.