In the present study, we have characterized the action of the natural cyclodepsipeptide jasplakinolide (JAS) on the cytoplasmic architecture, actin-based cytoplasmic motility, and the organization of the actin cytoskeleton in selected examples of green algae (Acetabularia, Pseudobryopsis and Nitella) and higher plant cells (Allium bulb scale cells and Sinapis root hairs). JAS was capable of influencing the actin cytoskeleton and inhibiting cytoplasmic streaming in a differential, cell type-specific manner. With the exception of Nitella, two consecutive responses were observed upon incubation with 2.5 microM JAS: In the first phase cytoplasmic streaming increased transiently alongside with minor modifications of the actin cytoskeleton in the form of adventitious actin spots and spikes appearing throughout the cell cortex in addition to the normal actin bundle system typical for each cell type. In the second phase, cytoplasmic streaming stopped and the actin cytoskeleton became heavily reorganized into shorter, straight, more and more randomly oriented bundle segments. JAS exerted severe long-term effects on the actin cytoskeleton when treatments exceeded 30min at a concentration of 2.5 microM. An in situ competition assay using equimolar concentrations of JAS and FITC-phalloidin suggested that JAS has a phalloidin-like action. Effects of JAS were significantly different from those of cytochalasin D with respect to the resulting degree of perturbance of cytoplasmic organization, the distribution of actin filaments and the speed of reversibility.