Effects of pharmacological agents and ATP on H2O2 production in P. euphratica cells under NaCl stress.

(A) H2O2 accumulation after 24 h of salt stress. Suspended cells, incubated with or without pharmacological agents (suramin, 300 µM; PPADS, 300 µM; and H-G, 50 mM glucose and 100 units/mL hexokinase) or glucose (50 mM), were exposed to NaCl (200 mM) or NaCl plus ATP (200 µM) for 24 h. Control cells were cultured with no addition of NaCl or any pharmacological agent. Bars represent the means of three independent experiments (in each 45 to 50 individual cells were quantified). Whiskers represent the error of the mean. Different letters (a, b, c) denote significant differences between treatments (P<0.01). (B) Early H2O2 production upon salt shock. Suspended cells were untreated (control) or pretreated without or with DPI (100 µM for 30 min), suramin (300 µM for 2 h), PPADS (300 µM for 2 h), or the H-G system (50 mM glucose and 100 units/mL hexokinase for 6 h), followed by exposure to NaCl (200 mM) with or without ATP (200 µM) supplementation. Transient production of H2O2 was recorded under a confocal microscope. Each point represents the mean of 15 to 18 individual cells from four independent experiments. Inserted panels show the H2DCF-dependent fluorescence intensity after 20–25 min of treatment. Different letters (a, b, c) denote significant differences between treatments (P<0.01).