XVI International Botanical Congess

The temperature-sensitive microtubule (MT) organization mutant mor1 provides a hopeful strategy for identifying factors regulating MT organization in plants. Cortical MTs shorten and lose transverse orientation in elongating cells of mor1 at 29?C. Within hours, impairment of cell growth anisotropy, organ spiralling, deformation of tip-growing root hairs and abolition of fertility occur. This suggests that the MOR1 gene regulates MT assembly and orientation and is crucial throughout development. Cytokinetic and mitotic MT arrays, however, appear to be unaffected and there is no indication of hormonal involvement. The phenotype of mor1 is excellent evidence that MTs regulate cell shape but our recent data suggest that the relationship with microfibril alignment is more complex than previously thought.