Induction of Actin‐Based Cytoplasmic Contraction in the Siphonous Green Alga Acetabularia (Chlorophyceae) by Locally Restricted Calcium Influx
- 1 May 1989
- journal article
- Published by Wiley in Botanica Acta
- Vol. 102 (2) , 164-171
- https://doi.org/10.1111/j.1438-8677.1989.tb00086.x
Abstract
Perfused cell segments dissected from the stalk or from detached cap ray chambers of Acetabularia were used as an experimental system to study the induction of cytoplasmic contractions and concurrent cytoskeletal changes in plant cells. Immunofluorescence microscopy revealed that the actin cytoskeleton quickly rearranges upon induction of contraction by forming bundles oriented circumferentially around the affected area, whereas microtubules were not detected. Contraction is blocked by cytochalasin D or N‐ethylmaleimide but is unaffected by microtubule specific inhibitors. Contraction requires external Ca2+ at concentrations of 1 μM or more, but fails to occur below 0.1 μM. Higher concentrations of Ca2+ up to 10 mM have no adverse effect. Contraction is prevented in the presence of micromolar Ca2+ by either 1 mM of the calcium channel blocker LaCl3 or 10 μM of the calmodulin inhibitor fluphenazine. Calcium ionophore A 23187 (1 μM) does not perturb wound contraction per se but causes the entire cytoplasm of wounded or unwounded cells to contract slowly. These data suggest that a localized influx of calcium ions at the wound edge causes major rearrangements in the distribution of cytoskeletal actin prior to contraction in Acetabularia. An involvement of calmodulin in calcium signaling is proposed.Keywords
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