Involvement of hydrogen peroxide and nitric oxide in salt resistance in the calluses from Populus euphratica

摘要

Nitric oxide (NO) and hydrogen peroxide (H(2)O(2)) function as signalling molecules in plants under abiotic and biotic stresses. Calluses from Populus euphratica, which show salt tolerance, were used to study the interaction of NO and H(2)O(2) in plant adaptation to salt resistance. The nitric oxide synthase (NOS) activity was identified in the calluses, and this activity was induced under 150 mM NaCl treatment. Under 150 mM NaCl treatment, the sodium (Na) percentage decreased, but the potassium (K) percentage and the K/Na ratio increased in P. euphratica calluses. Application of glucose/glucose oxidase (G/GO, a H(2)O(2) donor) and sodium nitroprusside (SNP, a NO donor) revealed that both H(2)O(2) and NO resulted in increased K/Na ratio in a concentration-dependent manner. Diphenylene iodonium (DPI, an NADPH oxidase inhibitor) counteracted H(2)O(2) and NO effect by increasing the Na percentage, decreasing the K percentage and K/Na ratio. N(G)-monomethyl-l-Arg monoacetate (NMMA, an NO synthase inhibitor) and 2-phenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxyde (PTIO, a specific NO scavenger) only reversed NO effect, but did not block H(2)O(2) effect. The increased activity of plasma membrane (PM) H(+)-ATPase caused by salt stress was reversed by treatment with DPI and NMMA. Exogenous H(2)O(2) increased the activity of PM H(+)-ATPase, but the effect could not be diminished by NMMA and PTIO. The NO-induced increase of PM H(+)-ATPase can be reversed by NMMA and PTIO, but not by DPI. Western blot analysis demonstrated that NO and H(2)O(2) stimulated the expression of PM H(+)-ATPase in P. euphratica calluses. These results indicate that NO and H(2)O(2) served as intermediate molecules in inducing salt resistance in the calluses from P. euphratica under slat stress by increasing the K/Na ratio, which was dependent on the increased PM H(+)-ATPase activity.