Abstract
Transversely oriented cortical microtubule arrays have been proposed to be required for straight cell elongation.
The Arabidopsis thaliana spiral3 (spr3) mutant is impaired in cell elongation and exhibits right-handed helical growth in axial organs. In elongating epidermal cells of spr3 roots, cortical microtubules were arranged in left-handed helical arrays, in contrast to wild-type transverse arrays. Map-based cloning revealed that SPR3 protein has homology to gamma tubulin ring protein84 (Grip84). In fungi and animal cells, Grip84 is a component of the γ-tubulin ring complex (γ-TuRC) which shows core nucleating activity of microtubules. We found that spr3 mutant has an amino acid substitution mutation in a highly conserved grip motif. Phenotypes of spr3 indicate that a defect in microtubule nucleation affects dynamics of cortical microtubules and leads to alteration in array organization.
We are analyzing γ-TuRC in wild-type Arabidopsis and spr3 mutant.
