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Biochemical and biophysical pH clamp controlling Net H+ efflux across the plasma membrane of plant cells

Wegner, LH, Li, X, Zhang, J, Yu, M, Shabala, S ORCID: 0000-0003-2345-8981 and Hao, Z 2021 , 'Biochemical and biophysical pH clamp controlling Net H+ efflux across the plasma membrane of plant cells' , New Phytologist, vol. 230, no. 2 , pp. 408-415 , doi: 10.1111/nph.17176.

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P-type H+ ATPases mediate active H+ efflux from plant cells. They generate a proton motive force across the plasma membrane, providing the free energy to drive the transport of other solutes, partly by coupling to H+ influx. Wegner & Shabala (2020) recently suggested that passive H+ influx can exceed pump-driven efflux due to ‘active buffering’, that is, cytosolic H+ scavenging and apoplastic H+ generation by metabolism (‘biochemical pH clamp’). Charge balance is provided by K+ efflux or anion influx. Here, this hypothesis is extended to net H+ efflux: even though H+ pumping is faster than backflow via symporters and antiporters, a progressive increase in the transmembrane pH gradient is avoided. Cytosolic H+ release is associated with bicarbonate formation from CO2. Bicarbonate serves as substrate for the PEPCase, catalyzing the reaction from phosphoenolpyruvate to oxaloacetate, which is subsequently reduced to malate. Organic anions such as malate and citrate are released across the plasma membrane and are (partly) protonated in the apoplast, thus limiting pump-induced acidification. Moreover, a ‘biophysical pH clamp’ is introduced, that is, adjustment of apoplastic/cytosolic pH involving net H+ fluxes across the plasma membrane, while the gradient between compartments is maintained. The clamps are not mutually exclusive but are likely to coexist.

Item Type: Article
Authors/Creators:Wegner, LH and Li, X and Zhang, J and Yu, M and Shabala, S and Hao, Z
Keywords: pH clamp, plasma membrane, H+ ATPase pump
Journal or Publication Title: New Phytologist
Publisher: Wiley-Blackwell Publishing Ltd.
ISSN: 1469-8137
DOI / ID Number: 10.1111/nph.17176
Copyright Information:

© 2021 The Authors. New Phytologist © 2021 New Phytologist Foundation.

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