Cadmium and paraquat toxicity in transgenic tabacco catalase deficient plants.

IANNONE MF, GROPPA MD, BENAVIDES MP

Mar del Plata, Argentina

Congreso; XLIII Reunion Anual Sociedad Argentina de Investigacion en Bioquimicay Biologia Molecular (SAIB); 2007

SAIB

Cadmium produces oxidative stress in several plant species. The aim of this work was to evaluate Cd2+ toxicity in transgenic tobacco catalase-deficient plants, giving a deeper insight in Cd2+ toxicity mechanisms by comparing its effect with that of paraquat, a well known oxidative stress inductor. Leaf discs from 40-day old transgenic CAT AS1 and wild type SR1 plants were incubated in a rotatory shaker for 3, 14 or 21 h with 500 ìM Cd2Cl or 100 ìM paraquat. Paraquat greatly increased electrolyte leakage from 14 h on, but TBARS only increased at 21h, both in CAT AS1 and SR1 plants. Cadmium slightly increased electrolyte leakage and did not evidence lipid peroxidation neither in CAT AS1 nor in SR1 plants. CAT expression decreased in CAT AS1 plants as expected, but Cd2+ and paraquat increased its expression by 50% at 3 h. Surprisingly, O2.- and H2O2 were significantly reduced by paraquat in both type of plants whereas Cd2+ slightly increased O2.- but reduced H2O2. However, other peroxidases, like ascorbate and guayacol peroxidases, are also decreased by both stressors and did not seem to be involved in H2O2 detoxification to compensate CAT deficiency. The results suggest that CAT deficient plants are damaged by paraquat, but not by Cd2+ used in concentrations that are toxic to other species, revealing that different mechanisms are involved in Cd2+ and paraquat toxicity in tobacco.