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.

Receptor-Like Activity Evoked by Extracellular ADP in Arabidopsis Root Epidermal Plasma Membrane

“…Here, the extracellular ADP-induced [Ca 2+ ] cyt response was operative over a wide pH range but activity at more neutral to alkaline pH suggests that extracellular ADP (and ATP) signaling could operate during stress responses in which the cytosol acidifies and apoplastic pH elevates above its normal acid value, such as hypoosmotic stress or elicitor challenge (Mathieu et al, 1996;Pugin et al, 1997;Beffagna et al, 2005). Additionally, pH dependence of ADP-or ATP-induced Ca 2+ and K + flux could be relevant at growth points, such as the root hair apex, at which apoplastic pH oscillates and pH oscillations are linked to nitrogen availability (Monshausen et al, 2007;Bloch et al, 2011).…”

“…Recording conditions as Figure 6. suspension cells, both hyper-and hypoosmotic stress trigger Ca 2+ influx but only hypoosmotic stress results in extracellular H 2 O 2 accumulation (Beffagna et al, 2005). Extracellular superoxide anions (resulting from perception of extracellular purine nucleotides) could generate H 2 O 2 that could then be translocated to the cytosol by PM aquaporins (Bienert et al, 2007;Dynowski et al, 2008).…”

Polyamines Interact with Hydroxyl Radicals in Activating Ca2+ and K+ Transport across the Root Epidermal Plasma Membranes

“…The PM H + pump is also activated by hyperosmotic stress or salt. This increases cytosolic pH, which leads to a lower synthesis of NADPH, thus decreasing its availability for NADPH oxidase (Beffagna et al, 2005 (Fig. 5B).…”

“…1A). Eosine yellow (EY; 0.5 mM), a specific inhibitor of the PM Ca 2+ pump (Romani et al, 2004;Beffagna et al, 2005) and is sensitive to EY (Fig. 1B), suggesting the Ca 2+ -ATPase as a possible candidate (White and Broadley, 2003).…”

Genetic and Molecular Aspects of Plant Response to Drought in Annual Crop Species

“…Changes in membrane integrity and modulation of lipid synthesis are key factors in the primary sensing of abiotic stress (Kader & Lindberg, 2010). Secondary, osmotic stress-induced signalling involves changes in plasma membrane H + -ATPase and Ca 2+ -ATPase activities that trigger concerted changes of Ca 2+ influx, cytoplasmic pH, and apoplastic production of ROS (Beffagna et al, 2005). Transcription factors represent the first level of regulation of mRNA metabolism, controlling the synthesis of pre-mRNA.…”