Short Communication Aberrant Cell Plate Formation in the Arabidopsis thaliana microtubule organization 1 Mutant

tubule-associated protein in Arabidopsis thaliana but differ-ent alleles have contradictory phenotypes. The original mutant mor1 alleles were reported to have disrupted corti-cal microtubules, swollen organs and normal cytokinesis, whereas other alleles, embryo-lethal gemini pollen 1 (gem1), have defective pollen cytokinesis. To determine whether MOR1 functions generally in cytokinesis, we examined the ultrastructure of cell division in roots of the original mor1-1 allele. Cell plates are misaligned, branched and meander-ing; the forming cell plates remain partly vesicular, with electron-dense or lamellar content. Phragmoplast micro-tubules are abundant but organized aberrantly. Thus, MOR1 functions in both phragmoplast and cortical arrays