Rearrangement of cortical microtubules from transverse to oblique or longitudinal in living cells of transgenicArabidopsis thaliana

Summary AGFP-TUA6 (-tubulin 6) gene was transduced in theArabidopsis thaliana genome, and the GFP-TUA6 protein was expressed by 20% of the total -tubulin amount. The expressed GFP-TUA6 protein was incorporated into cortical microtubules (cMTs), so that the cMTs could be visualized under the fluorescence microscope in the living cells. The rearrangement of cMTs was observed at the tangential epidermal cell face of the hypocotyl. At the initial stage of light-induced cMT rearrangement from a transverse to an oblique or a longitudinal orientation, randomly oriented short MTs appeared. These MTs rapidly elongated obliquely or longitudinally as the transverse cMTs shortened. Finally, the transverse cMTs were replaced by the newly organized oblique or longitudinal cMTs. Reorganization of the cMTs took 50–70 min. Treatment of seedlings with 5 × 10^–5 M cytochalasin B induced disarrayed cMTs. The involvement of cytochalasin B in the orientation of developing MTs is discussed.