ABIOTIC STRESS AND ANTIOXIDANT ENZYMES EXPRESSION IN SUNFLOWER LEAF DISCS

YANNARELLI GG; AZPILICUETA CE; GALLEGO SM; BENAVIDES MP; TOMARO ML

Iguazú, Misiones

Congreso; XL Reunión Anual Sociedad Argentina de Investigación Bioquímica y Biología Molecular; 2004

SAIB

Overproduction of reactive oxygen species (ROS) occur in plants under abiotic stress conditions. Although ROS act as mediators of oxidative damage, a signalling role for O2- and H2O2 has been proposed. In the present work, the effect of cadmium (300 and 500 µM CdCl2) or UVB radiation (30 KJ/m2) on expression of Cu-Zn superoxide dismutase (sod3) and catalase (cat1 and cat3) was evaluated in sunflower (Helianthus annuus L.) leaf discs. Samples were collected at 0, 4, 8, 12 and 16 h of Cd treatments or white light recuperation after UVB treatment. RNA extractions and semicuantitative RT-PCR analysis were performed. Treatment of 300 µM Cd induced 6.4, 2.9 and 6 fold the expression of  sod3, cat1 and cat3 over the controls, respectively, after 8 h of treatment, but 500 µM Cd showed lesser induction levels. Immediately after UVB irradiation, the mRNA of the three enzymes decreased. After 8 h of white light recovery, cat1 and cat3 were induced (1.9 and 3.5 fold, respectively) and the maximum sod3 expression was observed at 12 h (7 fold), respect to control. In conclusion, the balance between superoxide dismutase and peroxidases activities in cells is crucial for determining the steady-state level of O2- and H2O2. In our assay conditions, sod3, cat1 and cat3 were induced in response to abiotic stress at a late phase (8-12 h). The main induction of cat3 suggests that core-catalases of peroxisomes might play a key regulatory role in controlling H2O2 level.