9726968 Brown This project is to continue light and electron microscopic studies on the role of the cytoskeleton in pollen morphogenesis in higher plants. The project will be a comparison of pollen development in three systems: orchids (Orchidaceae), grasses (Poaceae) and sedges (Cyperaceae). The developing pollen cells of each exhibit a complex but characteristic set of meiotic and mitotic divisions, nuclear movements, and other events that establish polarized or asymmetric pollen structures. Based on detailed descriptions of normal events, experiments are designed in which either the microtubule or actin arrays are perturbed to assess the role these cytoskeletal elements play in determining the developmental patterns of the pollen. Cells will be exposed to various drugs (colchicine, cytochalasin D) known to affect microtubules or actin filaments, specific antibodies (anti-gamma tubulin, anti-integrins) and other agents in order to disrupt those cytoskeletal elements which appear to be involved in specific cellular events during pollen formation. Experiments will also be undertaken to examine the role of apoptosis. The project will provide fundamental comparative information on pollen development in higher plants and will document basic mechanisms by which the cytoskeleton determines cell polarity and tissue asymmetry. ***
