Hyperosmotic stress induces formation of tubulin macrotubules in root-tip cells of Triticum turgidum: their probable involvement in protoplast volume control.
Treatment of root-tip cells of Triticum turgidum with 1 M mannitol solution for 30 min induces microtubule (Mt) disintegration in the plasmolyzed protoplasts. Interphase plasmolyzed cells possess many cortical, perinuclear and endoplasmic macrotubules, 35 nm in mean diameter, forming prominent arrays. In dividing cells macrotubules assemble into aberrant mitotic and cytokinetic apparatuses resulting in the disturbance of cell division. Putative tubulin paracrystals were occasionally observed in plasmolyzed cells. The quantity of polymeric tubulin in plasmolyzed cells exceeds that in control cells. Root-tip cells exposed for 2-8 h to plasmolyticum recover partially, although the volume of the plasmolyzed protoplast does not change detectably. Among other events, the macrotubules are replaced by Mts, chromatin assumes its typical appearance and the cells undergo typical cell divisions. Additionally, polysaccharidic material is found in the periplasmic space. Oryzalin and colchicine treatment induced macrotubule disintegration and a significant reduction of protoplast volume in every plasmolyzed cell type examined, whereas cytochalasin B had only minor effects restricted to differentiated cells. These results suggest that Mt destruction by hyperosmotic stress, and their replacement by tubulin macrotubules and putative tubulin paracrystals is a common feature among angiosperms and that macrotubules are involved in the mechanism of protoplast volume regulation.
Faculty of Biology, Department of Botany, University of Athens, Athens 157 84, Greece.
George
G
Komis
Panagiotis
P
Apostolakos
Basil
B
Galatis
D000222:Adaptation, Physiological / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D003078:Colchicine / Q000494:pharmacology; D003460:Crystallization; D003571:Cytochalasin B / Q000494:pharmacology; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D004136:Dinitrobenzenes / Q000494:pharmacology; D007150:Immunohistochemistry; D008353:Mannitol / Q000494:pharmacology; D008854:Microscopy, Electron; D009997:Osmotic Pressure / Q000187:drug effects; D018518:Plant Root Cap / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D011523:Protoplasts / Q000187:drug effects / Q000502:physiology*; D013424:Sulfanilamides; D014908:Triticum / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D014404:Tubulin / Q000096:biosynthesis*
D004136:Dinitrobenzenes; D013424:Sulfanilamides; D014404:Tubulin; D003571:Cytochalasin B; D008353:Mannitol; C012465:oryzalin; D003078:Colchicine