ARABIDOPSIS THALIANA PLANTS GENERATING H2O2 IN CHLOROPLASTS: A BRAND NEW OXIDATIVE STRESS INDUCIBLE MODEL

SCARPECI TELMA ELEONORA; FAHNENSTICH HOLGER; VALLE ESTELA MARTA; MAURINO VERÓNICA

Rosario, Santa Fe

Congreso; XIII Reunión Latinoamericana XXVII Reunión Argentina de Fisiología Vegetal; 2008

Sociadad Argentina de Fisiología Vegetal

ROS are key molecules in the regulation of plant development, stress responses and programmed cell death. Previous studies indicate that depending on the type of ROS or its subcellular production site, different cellular responses are provoked. Arabidopsis thaliana expressing glycolate oxidase (GO) in chloroplasts were produced to study the antioxidant response of plants, due to ROS generated in chloroplast. The transformants accumulate hydrogen peroxide (H2O2) and glyoxylate in chloroplast and develop oxidative stress lesions under photorespiratory conditions but grow like the wild-type under non-photorespiratory conditions. Clear H2O2 accumulation was observed in the GO overexpressing lines after exposition to 200 µmol quanta m-2 s-1 by DAB staining, but not in leaves of plants grown at low photon fluxes (30 µmol quanta m-2 s-1). The antioxidant machinery of GO overexpressing lines was analyzed by determining APX and CAT activities in solution and SOD activity in native protein gels. In comparison to control plants in the same conditions, the GO plants presented a significant enhancement of the total APX activity at 75 µmol quanta m-2 s-1 and after 6 h exposition to 200 µmol quanta m-2 s-1. In the GO plants no significant change in the total CAT activity was observed at 75 and 200 µmol quanta m-2 s-1 when compared with the wild-type. The SOD activity gel showed that the intensity of the bands corresponding to the Mn and FeSOD were similar in both genotypes, whereas the intensity of the CuZnSOD doublet band was enhanced in the GO plants. Expression analysis by qRT-PCR indicated a clear induction in the accumulation of sHSP, WRKY30 and Fer1 transcripts in GO expressing lines at high light intensities in contrast to the control plants. Hence, the GO plants are an ideal no-invasive model system to study the effects of H2O2 directly in the chloroplasts because in these plants H2O2 accumulation is inducible and sustained perturbations can reproducibly be provoked by exposing the plants to different ambient conditions.