Plant and Cell Physiology, 1985, Vol. 26, No. 4 737-744
© 1985
Article |
Reactivation of Cytoplasmic Streaming in a Tonoplast-Permeabilized Cell Model of Acetabularia
Department of Biology, College of General Education, Osaka University Toyonaka, Osaka 560, Japan
To find whether cytoplasmic streaming in Acetabularia is controlled by Ca2+, a tonoplast-permeabilized cell model was prepared using a vacuolar perfusion technique. The cytoplasmic streaming remained almost normal after perfusion with EGTA medium (10 mM EGTA, 40 mM PIPES, 5mM MgCl2 and 800 mM sorbitol, pH 6.9), but stopped within 10 min when saponin medium (EGTA medium plus 50 µg/ml saponin, 50 µg/ml hexokinase and 5 mM glucose) was perfused. This model system was reactivated with a solution containing 0.5 mM ATP and different concentrations of Ca2+ (reactivation medium). With the reactivation medium at pCa 6–5, the resumed streaming lasted for about 10 min before the cytoplasm aggregated. At pCa 4–3, the streaming was observed only for a few minutes because the cytoplasm aggregated quickly. At pCa 7, no reactivated movement was observed. Reactivation was not induced in an ATP- or Mg2+-deficient medium even in the presence of an adequate concentration of Ca2+, and was inhibited by 50 µg/ml cytochalasin B or 1 mM N-ethylmaleimide.
We concluded from these observations that the cytoplasmic streaming in Acetabularia is very likely to be driven by the actomyosin system in the presence of Mg-ATP and Ca2+ at pCa 6–5.
(Received October 31, 1984; Accepted April 1, 1985)
CiteULike 
Connotea 
Del.icio.us What's this?