Development and validation of metabolic models to simulate the operation and interaction of antioxidant systems

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Antioxidant systems provide protection against reactive oxygen species (ROS) produced as a are result of environmental stresses. They also control the concentrations of H2O2 and O2- which play roles as signaling intermediates to switch the metabolism between defence and growth. Because of the complexity of antioxidant systems and their presence in all subcellular compartments, it is not yet understood, how these systems function in a highly dynamic and co-ordinated network to regulate the steady state levels of ROS. The goal of this proposal is to increase the theoretical understanding of antioxidant networks by means of based-computer modeling and validation experiments. For this purpose, we will develop modules based on biochemical and physico-chemical properties of antioxidant sytems to simulate redox-reactions in differnt subcellular compartments. These modules will be connected to account for transport. For validation, two approaches will be used: (a) Model adjustment by data obtained by analysis of knock-out mutants of chloroplastic, mitochondrial and cytosolic enzymes of the ascorbate-glutathione cycle in Arabidopsis provided by USA-partners in an associated project and (b) Testing selected model predictions with respect to ascorbate/H2O2 metabolism by use of radiotracers and by mapping and quantification of H2O2 in different subcellular compartments using TEM-EDX.