Preview

PDF, English Download (1MB) | Terms of use

Abstract

The aim of this work is the analysis of the vacuolar pH homeostasis in Arabidopsis thaliana root cells by means of computational modeling. The pH is an important parameter for a range of cellular processes such as the control of enzyme activity and the maintenance of osmotic pressure acting through the establishment of a proton motive force across the vacuolar membrane that in turn is used in the homeostasis of other ions on both sides of the membrane. Although many processes are known to be important for the establishment and maintenance of an acidic vacuolar lumen, recent experimental results have shown that our current understanding of those processes is not complete. To study the vacuolar pH homeostasis in an integrative manner, this work focuses on three different aspects. In the first part, an overview over computational systems biology approaches in Arabidopsis thaliana is given to demonstrate the state of the art and put the rest of the work in a broader context. The second part then focuses on transmembrane transport reactions and the importance of the correct scaling of the kinetic rate laws of those reactions in mathematical models employing sets of ordinary differential equations, which is of importance for any multi-compartment model such as the one presented in part three of this thesis. In the third part, a mathematical modeling approach is subsequently used to explain experimental data concerning the vacuolar pH homeostasis. To do so, three hypotheses of the mechanisms contributing to vacuolar acidification are developed: An as of yet unknown direct proton import, protons released by protein degradation and the reversal of a proton-calcium antiporter. Each of those hypotheses is implemented in an ordinary differential equations model and tested for feasibility against the experimental data.