Modulation of Heme oxigenase reponse by nitric oxide in ultraviolet-irradiated soybean plants

YANNARELLI G.; SANTA CRUZ, D; NORIEGA G.O.; TOMARO, M.L

Rosario, Argentina

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

Sociedad Argentina de Bioquímica y Biología Molecular

We have previously shown that heme oxygenase (HO) is upregulated by ROS and protects soybean leaves against UV-Bradiation. In the present study, we evaluated whether nitric oxide  (NO) could enhance this protection mechanism by modulating HOresponse to UV-B-induced oxidative stress. Soybean (L.) plants were treated with different sodium nitroprussiate (SNP)concentrations before UV-B irradiation (30 kJ m ). Pretreatments with 0.8 or 1.2mMSNP prevented chlorophyll loss and ion leakagein UV-B treated plants. These SNP doses reduced by 80%, both theaccumulation of H O and the production of O . transcript levels were diminished by 63% after irradiation, whereas SNP pretreatment enhanced gene expression up to 100%, respect to controls. HO activity showed a positive correlation with transcript levels. The presence of cPTIO, a specific NO scavenger, avoided up-regulation. On the other hand, 0.4 or 1.6mMSNP 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 gene expression. Our data indicate thatNOacts as an antioxidant and modulates HO activity. Moreover, overexpression involves not only ROS, but also NO. This mechanism could explain, at least in part, the protective role of NO againstUV-B radiation.