Poster: Oxidative Stress
Abs #
139: Regulation of antioxidative enzymes during leaf senescence of Arabidopsis thaliana
The final step of the development that leads to the death of an organism is the phenomenon of senescence. Senescence is a highly regulated and endogenously controlled process. Free radicals are thought to play an essential role in senescence especially those derived from oxygen. The levels of the different activated oxygen species appear to be tightly regulated and may serve as signalling molecules. Therefore, a coordinated regulation of the oxygen free radical scavenging enzymes is essential. Catalase 2 (CAT2) and ascorbate peroxidase (APX) activities decreased with the time of bolting. At the same time point, the H2O2 content increased. Subsequently, the stress inducible CAT3 isoform was activated and APX activity was recovered, leading to a decline of H2O2 content. The APX activity was inhibited by H2O2 in suspension cells and detached leaves during time of bolting. Therefore, the initial step of this process seems to be the down regulation of the CAT2 isoform and the decrease in APX activity might be a secondary effect. Currently, we are characterizing factors, which interact with the cat2 promoter and might be involved in the regulation of gene expression. Four proteins have already been identified to be involved in complex formation with the cat2 promoter. The functional role of these proteins is analysed in transgenic approaches. Furthermore, catalase overexpressing and knockout plants are investigated.
