Dear Editor,Anisotropic cell expansion is a property of plant cells that is dependent upon the formation of a highly ordered cortical microtubule (Mr) array.The orientation of cortical microtubules is critical for guiding cellulose synthase complexes in the plasma membrane and thereby determining the direction of the cell expansion (Paredez et al.,2006).Recent work has demonstrated a link between MT organization and stresses experienced by the cell during plant cell development (Uyttewaal et al.,2012;Sampathkumar et al.,2014),but how order is generated within the cortical microtubule array has been much debated (Dixit and Cyr,2004;Wightman and Tuer,2007).