Modulation of heme oxygenase response by nitric oxide in ultraviolet-B irradiated soybean plants

YANNARELLI GUSTAVO; SANTA CRUZ DIEGO; NORIEGA GUILLERMO; TOMARO MARIA LUJAN

Mar del Plata, Buenos Aires, Argentina

Congreso; XLIII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2007

We have previously shown that heme oxygenase (HO) is up-regulated by ROS and protects soybean leaves against UV-B radiation. In the present study we evaluated whether nitric oxide (NO) could enhance this protection mechanism modulating HO behavior against UV-B-induced oxidative stress. Soybean (Glycine max L.) plants were treated with different sodium nitroprussiate (SNP) concentrations before UV-B irradiation (30 kJ m-2). Pretreatments with 0,8 or 1,2 mM SNP prevented chlorophyll loss and ion leakage in UV-B treated plants. These SNP doses also reduced by 80% the accumulation of H2O2 and O2.- induced by UV-B. HO-1 transcript levels were diminished by 63% after irradiation, whereas SNP pretreatment enhanced HO-1 gene expression up to 100% respect to controls. HO activity showed a positive correlation with HO-1 transcript levels. The presence of cPTIO, a specific NO scavenger, avoided HO-1 up-regulation. On the other hand, 0,4 or 1,6 mM SNP doses did not fully prevent the effects elicited by UV-B. Treatments with SNP in the absence of UV-B demonstrated that NO itself enhances HO-1 gene expression. Our data indicates that NO acts as an antioxidant and modulates HO activity. Moreover, HO-1 overexpression involves not only ROS, but also NO. This mechanism could explain, at least in part, the protective role of NO against UV-B radiation.