Localization of ubiquitin in anthers and pistils of Nicotiana

Ubiquitin-conjugated compounds were localized in anthers and pistils of Nicotiana alata by immuno-cytochemistry. In young anthers, antibodies to ubiquitin bound to callose cell walls surrounding pollen mother cells and to organelles in the endothecium. At the freespore stage, antibodies bound to circular-cell cluster cells subtending the stomium and to organelles and cell walls of endothecial cells. Near anther dehiscence, locular material was labeled. In pistils, cell walls of stylar transmitting tissue were labeled in a beaded pattern. Antibodies bound to a thin layer surrounding ovules, to the lining of embryo sacs, to cytoplasm of eggs and synergids, and to starch grains in central cells. Sites of localization were tissue- and time-specific, suggesting a regulatory role for ubiquitin in development of reproductive structures in flowering plants.