IMMUNOCYTOCHEMICAL LOCALIZATION OF ACTIN AND PROFILIN IN THE GENERATIVE CELL OF ANGIOSPERM POLLEN - TEM STUDIES ON HIGH-PRESSURE FROZEN ANDFREEZE-SUBSTITUTED LEDEBOURIA-SOCIALIS ROTH (HYACINTHACEAE)

Actin was demonstrated for the first time at the EM level in the gener ative cell of mature angiosperm pollen by using immune-gold labelling of high-pressure frozen and freeze-substituted Ledebouria socialis Rot h anthers. In addition, profilin, an actin-monomer binding protein, is shown to coexist in the generative cell. We attribute the detection o f actin and profilin to the applied cryomethods which yield a much bet ter preservation of ultrastructure and antigenicity of delicate cytosk eletal constituents than conventional fixation techniques. Actin label ling was observed within the cytoplasm of the generative cell and beca me especially clear in close vicinity to microtubular bundles. Filamen tous structures congruent with the actin labelling patterns do occur, but are not a frequent feature. Profilin was localised throughout the cytoplasm.