Abstract
In plant cells, many microtubule-associated proteins (MAPs) control various microtubule (MT) functions. Arabidopsis SPIRAL2 (SPR2) protein is a plant-specific MAP involved in the regulation of cortical MT arrays. SPR2 localizes to the cortical MTs, and the null mutation of SPR2 causes a shallow left-handed helical array in cortical MTs and a right-handed helical growth in longitudinally growing organs such as petiole. SPR2 has HEAT repeat motifs at the N-terminal region and highly conserved region among SPR2 homologs at the C-terminus. In MT binding assay in vitro, MTs directly bound to purified recombinant SPR2 protein independently at the N- and C-terminal regions. Furthermore, we examined the effect of SPR2 on the dynamics of MT in vitro.
