Theoretical Analysis of the Impact of the Plasma Membrane Н+-ATPase on the CO2 Entry into a Plant Cell
A decrease of the plasma membrane H+-ATPase activity in plant cells is an important factor involved in the development of stressor-induced responses and in signal reception. The aim of this work was to investigate theoretically the impact of the plasma membrane Н+-ATPase activity on the amount of CO2 entering a plant cell. We used our model of transport processes and electrogenesis in a plant cell, which takes into account transport systems of plasma membrane and tonoplast, including the H+-ATPase. The amount of CO2 entering a plant cell was estimated as the CO2 portion in the total amount of Ci in the external medium (PCO2), which was dependent on extracellular pH. Excitable and non-excitable cells were simulated. It was shown that a decrease in the H+-ATPase activity lowered PCO2 in both variants of the model. Dynamics of the PCO2 decrease had an extremum; later, a stationary value was reached. It is possible that dynamics of PCO2 decrease was related with Ca2+ flux into cytoplasm. It was also shown that magnitude of PCO2 was dependent on the magnitude of the H+-ATPase inactivation and initial activity of the enzyme. Thus, the analysis shows that inactivation of H+-ATPase can influence the amount of CO2 entering a plant cell. This effect may be involved in the regulation of photosynthetic processes.