Optimizing Oxygenic Photosynthesis: pH-Regulation of Electron Transport in Chloroplasts In Silico

In this work, we carried out mathematical modeling of the electron and proton transport regulation in the thylakoid membranes of chloroplasts under different operating conditions of the electron transport chain (ETC) of chloroplasts. The study is based on the kinetic model of the functioning of the chloroplasts ETC proposed by us earlier, which describes the redox transformations of the reaction center of photosystem 1 (PS1), ferredoxin molecules, several forms of plastoquinone (PS2-related molecules PQA, PQB, and the pool of plastoquinones PQ/PQH2), as well as plastocyanin molecules. The model also simulates the induction curve of chlorophyll a fluorescence in the leaves of higher plants adapted to darkness. The multiphase kinetic curves obtained by varying the model parameters reflecting the rate of functioning of the Calvin-Benson cycle and the cyclic electron transport path around PS1 are in reasonable agreement with the published experimental data. The main result of our work is that it mathematically describes how pH-dependent regulatory processes occurring in various parts of the chloroplast ETC (non-cyclic, cyclic, and pseudocyclic electron transport) affect the kinetics of induction processes (slow induction of fluorescence and redox transformations of the PS1 photoreaction center) in dark-adapted chloroplasts of plants.