Plant and Cell Physiology Advance Access originally published online on June 4, 2005
Plant and Cell Physiology 2005 46(8):1326-1339; doi:10.1093/pcp/pci142
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Modulation of Reactive Oxygen Species Production During Osmotic Stress in Arabidopsis thaliana Cultured Cells: Involvement of the Plasma Membrane Ca2+-ATPase and H+-ATPase
Istituto di Biofisica del CNR, Sezione di Milano, Dipartimento di Biologia, Università degli Studi di Milano, Via Celoria 26, 20133 Milano, Italy
* Corresponding author: E-mail, Nicoletta.Beffagna{at}unimi.it; Fax, +39-02-50314815.
In Arabidopsis thaliana cells, hypoosmotic treatment initially stimulates Ca2+ influx and inhibits its efflux and, concurrently, promotes a large H2O2 accumulation in the external medium, representative of reactive oxygen species (ROS) production. After the first 10–15 min, Ca2+ influx rate is, however, lowered, and a large rise in Ca2+ efflux, concomitant with a rapid decline in H2O2 level, takes place. The drop of the H2O2 peak, as well as the efflux of Ca2+, are prevented by treatment with submicromolar concentrations of eosin yellow (EY), selectively inhibiting the Ca2+-ATPase of the plasma membrane (PM). Comparable changes of Ca2+ fluxes are also induced by hyperosmotic treatment. However, in this case, the H2O2 level does not rise, but declines below control levels when Ca2+ efflux is activated. Also K+ and H+ net fluxes across the PM and cytoplasmic pH (pHcyt) are very differently influenced by the two opposite stresses: strongly decreased by hypoosmotic stress and increased under hyperosmotic treatment. The H2O2 accumulation kinetics, followed as a function of the pHcyt changes imposed by modulation of the PM H+-ATPase activity or weak acid treatment, show a close correlation between pHcyt and H2O2 formed, a larger amount being produced for changes towards acidic pH values. Overall, these results confirm a relevant role for the PM Ca2+-ATPase in switching off the signal triggering ROS production, and propose a role for the PM H+-ATPase in modulating the development of the oxidative wave through the pHcyt changes following the changes of its activity induced by stress conditions.
(Received March 17, 2005; Accepted May 26, 2005)
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