title: Anoxia-induced elevation of cytosolic Ca2+ concentration depends on different Ca2+ sources in rice and wheat protoplasts.
abstract: The anoxia-dependent elevation of cytosolic Ca(2+) concentration, [Ca(2+)](cyt), was investigated in plants differing in tolerance to hypoxia. The [Ca(2+)](cyt) was measured by fluorescence microscopy in single protoplasts loaded with the calcium-fluoroprobe Fura 2-AM. Imposition of anoxia led to a fast (within 3 min) significant elevation of [Ca(2+)](cyt) in rice leaf protoplasts. A tenfold drop in the external Ca(2+) concentration (to 0.1 mM) resulted in considerable decrease of the [Ca(2+)](cyt) shift. Rice root protoplasts reacted upon anoxia with higher amplitude. Addition of plasma membrane (verapamil, La(3+) and EGTA) and intracellular membrane Ca(2+)-channel antagonists (Li(+), ruthenium red and cyclosporine A) reduced the anoxic Ca(2+)-accumulation in rice. Wheat protoplasts responded to anoxia by smaller changes of [Ca(2+)](cyt). In wheat leaf protoplasts, the amplitude of the Ca(2+)-shift little depended on the external level of Ca(2+). Wheat root protoplasts were characterized by a small shift of [Ca(2+)](cyt) under anoxia. Plasmalemma Ca(2+)-channel blockers had little effect on the elevation of cytosolic Ca(2+) in wheat protoplasts. Intact rice seedlings absorbed Ca(2+) from the external medium under anoxic treatment. On the contrary, wheat seedlings were characterized by leakage of Ca(2+). Verapamil abolished the Ca(2+) influx in rice roots and Ca(2+) efflux from wheat roots. Anoxia-induced [Ca(2+)](cyt) elevation was high particularly in rice, a hypoxia-tolerant species. In conclusion, both external and internal Ca(2+) stores are important for anoxic [Ca(2+)](cyt) elevation in rice, whereas the hypoxia-intolerant wheat does not require external sources for [Ca(2+)](cyt) rise. Leaf and root protoplasts similarly responded to anoxia, independent of their organ origin.
authors.affiliation: Department of Genetics and Breeding, St. Petersburg State University, Universitetskaya em., 7/9, 199034, St. Petersburg, Russia. bootika@mail.ru
authors.forename: Vladislav V
authors.initials: VV
authors.lastname: Yemelyanov
authors.forename: Maria F
authors.initials: MF
authors.lastname: Shishova
authors.forename: Tamara V
authors.initials: TV
authors.lastname: Chirkova
authors.forename: Sylvia M
authors.initials: SM
authors.lastname: Lindberg
mesh_terms: D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015687:Cell Hypoxia; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002614:Chelating Agents / Q000494:pharmacology; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism*; D004533:Egtazic Acid / Q000494:pharmacology; D005456:Fluorescent Dyes; D016257:Fura-2 / Q000031:analogs & derivatives / Q000378:metabolism; D007811:Lanthanum / Q000494:pharmacology; D058503:Mesophyll Cells / Q000187:drug effects / Q000378:metabolism; D012275:Oryza / Q000187:drug effects / Q000378:metabolism*; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism; D018520:Plant Shoots / Q000187:drug effects / Q000378:metabolism; D011523:Protoplasts / Q000187:drug effects / Q000378:metabolism*; D036226:Seedlings / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction; D014908:Triticum / Q000187:drug effects / Q000378:metabolism*; D014700:Verapamil / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D002614:Chelating Agents; D005456:Fluorescent Dyes; C028521:lanthanum chloride; C049925:fura-2-am; D004533:Egtazic Acid; D007811:Lanthanum; D014700:Verapamil; D002118:Calcium; D016257:Fura-2