Mechanisms of Nitric Oxide Protection against the UV-B induced oxidative stress in Maize Seedlings

TOSSI, V LAMATTINA L, CASSIA R.

Mar del Plata

Congreso; XLIII Reunión Anual de la SAIB; 2007

SOciedad Argentina de Investigación en Bioquímica y Biología Molecular

The objective of this work was to characterize the effect of Nitric Oxide (NO) against the oxidative damage produced by UV-B in plants. Maize seedlings were maintained 10 days in normal conditions (H), or were pre-treated with two NO donors: Sodium Nitropruside (N) or ABA (A), which apparently induces antioxidant enzymes toward NO increase. Pre-treated seedling were irradiated 8 h with 3 W/m2 of UV-B (named Hi, Ai and Ni respectively).Twenty four hours after the irradiation, NO concentration was higher in Ni and Ai. DAB staining showed a high concentration of reactive oxygen species (ROS) in Hi seedling.. Catalase and ascorbate peroxidase activities were slightly increased in the first 4 hours of UV radiation, but then decrease to the control level, suggesting that antioxidant enzymatic activity is not the responsible for the ROS drop in Ni plants. We observed a greater UV-B absorption. when plants were treated with increasing concentrations of NPS. Ni seedlings show an increased concentration of flavonoids (other ROS scavengers). Interestingly, the flavonoids localization is coincident with the NO presence, in the irradiated surface of the Ni leaves. Our results indicate that NO increasing has no influence in the antioxidant enzymes activity, but reduces the oxidative stress generated by UV-B, absorbing the UV-B radiation and rising the localized concentration of other ROS scavengers.