Anoxia-induced elevation of cytosolic Ca2+ concentration depends on different Ca2+ sources in rice and wheat protoplasts

• Published in: Planta Vol. 234; no. 2; pp. 271 - 280
• Main Authors: Yemelyanov, Vladislav V., Shishova, Maria F., Chirkova, Tamara V., Lindberg, Sylvia M.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01-08-2011
• Subjects: Agriculture; Biomedical and Life Sciences; Calcium - metabolism; Calcium Channel Blockers - pharmacology; Cell Hypoxia; Cell Membrane - drug effects; Cell Membrane - metabolism; Chelating Agents - pharmacology; Cytosol - drug effects; Cytosol - metabolism; Ecology; Egtazic Acid - pharmacology; Fluorescent Dyes; Forestry; Fura-2 - analogs & derivatives; Fura-2 - metabolism; Lanthanum - pharmacology; Life Sciences; Mesophyll Cells - drug effects; Mesophyll Cells - metabolism; Original Article; Oryza - drug effects; Oryza - metabolism; Plant Leaves - drug effects; Plant Leaves - metabolism; Plant Roots - drug effects; Plant Roots - metabolism; Plant Sciences; Plant Shoots - drug effects; Plant Shoots - metabolism; Protoplasts - drug effects; Protoplasts - metabolism; Seedlings - drug effects; Seedlings - metabolism; Signal Transduction; Triticum - drug effects; Triticum - metabolism; Verapamil - pharmacology; Anoxic signalling; Cytosolic calcium; Fluorescence microscopy
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/s00425-011-1396-x

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.