CHARACTERIZATION AND IMMUNOCYTOCHEMICAL DISTRIBUTION OF MICROTUBULES AND F-ACTIN FILAMENTS IN PROTOPLASTS OF MIMOSA-PUDICA MOTOR CELLS

The rapid (1 second) seismonastic movement of Mimosa pudica pulvini is associated with a fast migration of ions (mainly K+, Cl- and Ca2+) le ading to a loss of turgor and skrinkage of the motor cells. A contract ile mechanism has been proposed to explain this fast response in these fully differentiated cells. The finding that cytoplasmic filaments ag gregate after the shrinkage of the cells was given as an argument in t his direction. Motor cell extracts contain proteins that comigrate wit h muscular actin and a protozoan tubulin in SDS electrophoresis. Moreo ver, these comigrating proteins cross-reacted on immunoblots with mono clonal antibodies against tubulin and actin. Finally, the location of these proteins was determined in motor cell protoplasts. Thus, F-actin and microtubules were vizualized using either fluorescent microscopy with fluorescent probes or using monoclonal antibodies localized with fluorescent probes or through immunogold-silver staining. The intracel lular location of these proteins respectively on cytoplasmic filaments and microtubules afford additional arguments as to their role as cont ractile and cytoskeletal components.