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

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