Abstract
The chloroplast movement in spinach mesophyll cells, which was induced by high-intensity blue light (460 nm, 50 μmol/m2 sec), was inhibited by an actin depolymerizing reagent cytochalasin B (100 μM) reversibly. BDM (2,3-butanedione monoxime), a myosin inhibitor, also inhibited the chloroplast movement reversibly in a concentration-dependent manner (0-100 mM). BDM did not seem to inhibit the chloroplast movement by disruption of the actin organization. Before actinic light irradiation, actin bundles looked like thin, mesh-like configuration surrounding each chloroplast. In contrast, actin filaments in cells irradiated with blue light became thick, straight bundles traversing the cell. On the other hand, red light (660 nm, 30 μmol/m2 sec) neither induced chloroplast movement nor affected the actin organization. Our results suggest that the actomyosin system plays a crucial role in the chloroplast movement in spinach mesophyll cells.
