Microtubule reorganization accompanying preprophase band formation in guard mother cells ofAvena sativa L.

Summary In order to study developmental changes in microtubule organization attending the formation of a longitudinally oriented preprophase band, the guard mother cells ofAvena were examined using a new procedure for anti-tubulin immunocytochemistry on large epidermal segments. We found that the interphase band (IMB) of transverse cortical microtubules present in these cells following asymmetric division is replaced after subsidiary cell formation by mesh-like to radial microtubules that extend throughout the cytoplasm. Many of the Mts are also grouped in bundles. Gradually, this intermediate array is succeeded by longitudinal elements of the PPB. Thus, preprophase band formation is accompanied by a 90° shift in Mt orientation, with a radial arrangement serving as an intermediate stage. The micrographs are most consistent with the rearrangement of intact Mts, although changes in Mt assembly are possible as well. The role of the IMB in guard mother cells is also discussed.Abbreviations GMC guard mother cell - IMB interphase microtubule band - Mt microtubule - PPB preprophase band