Calcium in the Control of Nitrogenase Activity in Vicia faba L. Root Nodules: Calcium Release from Symbiosomes and the Accompanying Decrease in Their Nitrogenase Activity Is Blocked by Verapamil |
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Authors: | V V Krylova I M Andreev P N Dubrovo I N Andreeva S F Izmailov |
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Institution: | (1) Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya ul. 35, Moscow, 127276, Russia |
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Abstract: | Treatment of root nodules or symbiosomes isolated from them with calcium chelator EGTA alone or together with calcium ionophore A23187 for 3 h under microaerophilic conditions considerably decreased their nitrogenase activity (NA). Under these experimental conditions, cytochemical electron-microscopic analysis revealed considerable calcium depletion of symbiosomes in the infected nodule cells treated with EGTA and A23187. Ca2+ channel blockers, verapamil and ruthenium red, inhibited EGTA-induced Ca2+ release from symbiosomes. In this case, NA insignificantly increased in the whole nodules and reached its initial level in symbiosomes. The experiments on isolated symbiosomes with arsenazo III, a Ca2+ indicator, demonstrated that verapamil inhibited Ca2+ release from them induced by valinomycin in the presence of K+ ions. These data suggest the presence on the peribacteroid membrane of a verapamil-sensitive transporter responsible for Ca2+ release from symbiosomes. A possible role of this transporter in the interaction between symbiotic partners in the infected cells of root nodules is discussed. |
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