Role of NADPH oxidases in the regulation of oxidative metabolism under cadmium stress

DK GUPTA; LB PENA; MC ROMERO-PUERTAS; LM SANDALIO

Budapest

Congreso; 10th International Conference on Reactive Oxygen and Nitrogen Species in Plants; 2011

Plant Oxygen Group of the Society for Free Radical Research-Europe

Different approaches have demonstrated that oxidative stress is one of the primary effects of Cd exposure, although the sources of reactive oxygen species involved are not well established (1). In this work, the role of NADPH oxidases as a source of ROS has been studied by using AtrbohC, D & F Arabidopsis mutants. In these mutants we analyzed the effect of 25 and 100 µM Cd for 1 and 5 days on growth parameters, H2O2 and NO accumulation, and on the activity and transcript levels of some antioxidants. Cadmium significantly decreased the germination rate of seeds and leaf biomass production at 100µM and after 5 days of treatment in WT plants, although this reduction was not observed in AtrbohF. Lipid peroxidation and H2O2 accumulation increased in line with the Cd concentration, mainly after 5 days of treatment, and no differences were observed between WT and Atrboh mutants. A different behaviour was observed with NO accumulation, which decreased with the treatment in all plants analyzed except AtrbohC. In WT plants, catalase activity slightly increased with the treatment and opposite effect was observed in Atrboh mutants, mainly due to changes in CAT2 expression. Cadmium increased glutathione reductase activity mostly in the mutants after 5 days of treatment with 100 µM Cd, although no changes were observed at transcriptional level. GSH and ASC content were also affected by the treatment mainly in AtrbohF mutants.  The activity of glycolate oxidase was also induced by 100 µM Cd in the mutants due to up-regulation of GOX3. In conclusion, down-regulation of different NADPH oxidases produces differential responses to Cd in Arabidopsis plants which affect mainly the regulation of antioxidant expression and photorespiration