title: Modulation of reactive oxygen species production during osmotic stress in Arabidopsis thaliana cultured cells: involvement of the plasma membrane Ca2+-ATPase and H+-ATPase.
abstract: 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 (pH(cyt)) 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 pH(cyt) changes imposed by modulation of the PM H+-ATPase activity or weak acid treatment, show a close correlation between pH(cyt) 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 pH(cyt) changes following the changes of its activity induced by stress conditions.
authors.affiliation: Istituto di Biofisica del CNR, Sezione di Milano, Dipartimento di Biologia, Università degli Studi di Milano, Via Celoria 26, 20133 Milano, Italy. Nicoletta.Beffagna@unimi.it
authors.forename: Nicoletta
authors.initials: N
authors.lastname: Beffagna
authors.forename: Barbara
authors.initials: B
authors.lastname: Buffoli
authors.forename: Chiara
authors.initials: C
authors.lastname: Busi
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002478:Cells, Cultured; D006861:Hydrogen Peroxide / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D017136:Ion Transport; D009997:Osmotic Pressure; D011188:Potassium / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D011522:Protons; D017382:Reactive Oxygen Species
chemical_list: D011522:Protons; D017382:Reactive Oxygen Species; D006861:Hydrogen Peroxide; D006180:Proton-Translocating ATPases; D000252:Calcium-Transporting ATPases; D011188:Potassium; D002118:Calcium