Abstract
Proton pumps create a proton motif force and thus, energize secondary active transport at the plasma nmembrane and endomembranes of the secretory pathway. In the plant cell, the dominant proton pumps are the plasma membrane ATPase, the vacuolar pyrophosphatase (V-PPase), and the vacuolar-type ATPase (V-ATPase). All these pumps act on the cytosolic pH by pumping protons into the lumen of compartments or into the apoplast. To maintain the typical pH and thus, the functionality of the cytosol, the activity of the pumps needs to be coordinated and adjusted to the actual needs. The cellular toolbox for a coordinated regulation comprises 14-3-3 proteins, phosphorylation events, ion concentrations, and redox-conditions. This review combines the knowledge on regulation of the different proton pumps and highlights possible coordination mechanisms.
Highlights
Central reactions, such as glycolysis, nitrate reduction, antero, and retrograde signaling take place in the cytosol, but the cytosol is a transit compartment for many solutes, which reside transiently in the cytosol subsequent uptake and before compartmentation into organelles
In A. thaliana, Cys256 mediates sensitivity of V-ATPase ATP-hydrolysis toward redox changes, while proton pumping activity is Cys256independently inhibited by H2O2
Though more data are required on some regulatory mechanism, it is plausible that coordinated regulation of plant proton pumps occurs on several levels with respect to the growth conditions
Summary
Central reactions, such as glycolysis, nitrate reduction, antero-, and retrograde signaling take place in the cytosol, but the cytosol is a transit compartment for many solutes, which reside transiently in the cytosol subsequent uptake and before compartmentation into organelles. The PM-ATPase functions in the re-acidification of the apoplast subsequent alkalization (Geilfus, 2017; Feng et al, 2020), while hyperpolarization is driven by PM-ATPase under acid stress, followed by electrical balancing by potassium symporters and Abbreviations: V-ATPase, vacuolar-type ATPase; PM-ATPase, plasma membraneATPase; V-PPase, vacuolar pyrophosphatase; NHX, Na+/H+-antiporter. Assuming lack of coordination of transport processes at tonoplast and plasma membrane, the cytosolic solute concentration would putatively increase by 150 mM/min in guard cells during stomata opening (Cubero-Font and de Angeli, 2020).
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