Protective effect of nitric oxide against oxidative stress under ultraviolet-B radiation.

Abstract The response of bean leaves to UV-B radiation was extensively investigated. UV-B radiation caused increase of ion leakage, loss of chlorophyll, and decrease of the maximum efficiency of PSII photochemistry ( F v / F m ) and the quantum yield of PSII electron transport ( Φ PSII ) of bean leaves. H 2 O 2 contents and the extent of thylakoid membrane protein oxidation increased, indicated by the decrease of thiol contents and the increase of carbonyl contents with the duration of UV-B radiation. Addition of sodium nitroprusside, a nitric oxide (NO) donor, can partially alleviate UV-B induced decrease of chlorophyll contents, F v / F m and Φ PSII . Moreover, the oxidative damage to the thylakoid membrane was alleviated by NO. The potassium salt of 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, a specific NO scavenger, arrested NO mediated protective effects against UV-B induced oxidative damage. Incubation of thylakoid membrane with increasing H 2 O 2 concentrations showed a progressive enhancement in carbonyl contents. H 2 O 2 contents were decreased in the presence of NO under UV-B radiation through increased activities of superoxide dismutases, ascorbate peroxidases, and catalases. Taken together, the results suggest that NO can effectively protect plants from UV-B damage mostly probably mediated by enhanced activities of antioxidant enzymes.