The damage to AC made by external EGTA depleting the Influencedark adaptedandandmagnesiumlight irradiated actin selleckchem net Influence of calcium and magnesium ions on the actin network in dark adapted and weak light irradi ated cells. Samples were incubated for 2 h with 5 mM Ca2 or 5 mM Mg2. Actin cytoskeleton in the dark adapted cells and after irradiation with continuous weak red light for 1 h. Scale bars, 10 m. The differences observed in tobacco are in contrast to the results obtained with fixed tissue of A. thaliana, where no structural dissimilarities of actin were detected between leaves treated with wBL or SBL. The different suscep tibility of actin to light in Arabidopsis as compared to Nico tiana might be attributed to a non identical organization of the filament bundles in these species.

This could account for three unsuccessful attempts to transform Ara bidopsis leaves with the plastin GFP construct used in this study whereas siliques and sepals showed an effective transformation. On the other hand, the discrepancy between the actin images obtained Inhibitors,Modulators,Libraries for SBL irradiated tobacco and Arabidop sis could be a consequence of the fixation procedure used for the latter species. Seeking BL specific actin reorganization we compared the effects of blue and red light on the actin cytoskeleton. As with fixed cells, RL and BL effects were similar, even though RL induces no directional chloroplast movement in tobacco. This lack of difference confirms our pre vious conclusion that Inhibitors,Modulators,Libraries the directionality of chloroplast responses is not based on BL specific changes of F actin, and that other Inhibitors,Modulators,Libraries factor must determine the direction of chloroplast movement.

Inhibitors,Modulators,Libraries cytosolic Ca2 confirms the obvious fact that calcium is important for the maintenance of microfilament integrity. The formation of the well structured filamentous actin on the surfaces of chloroplasts may be due to Ca2 extraction from these organelles during wBL irradiation. Blue light of 1 mol m 2 s 1 produced a transient increase in cytosolic Ca2 in A. thaliana leaves, which originated partly from internal calcium stores. Our results can be interpreted in terms of BL causing an efflux Inhibitors,Modulators,Libraries of calcium from chloroplasts, and its continuous chelating by extra cellular EGTA. This combined action of light and EGTA might have induced the transient formation of fine actin baskets on chloroplast surfaces, whereas EGTA prevented a stable restoration of actin cytoskeleton in the cells.

Along with the destruction of the actin network, EGTA strongly inhibited chloroplast selleck kinase inhibitor responses in tobacco, simi lar to the effects previously reported for ferns and water angiosperms. Combined treatment with EGTA and A23187 merely accelerated and intensified the effects of EGTA. The ionophore facilitated the efflux of calcium from the cells.