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Abstract

The membrane-bound proton-pumping pyrophosphatase (V-PPase), together with the V-type H+ -ATPase, generates the proton motive force that drives vacuolar membrane solute transport. Transgenic plants constitutively overexpressing V-PPases were shown to have improved salinity tolerance, but the relative impact of increasing PPi hydrolysis and protonpumping functions has yet to be dissected. For a better understanding of the molecular processes underlying V-PPase-dependent salt tolerance, we transiently overexpressed the pyrophosphate-driven proton pump (NbVHP) in Nicotiana benthamiana leaves and studied its functional properties in relation to salt treatment by primarily using patch-clamp, impalement electrodes and pH imaging. NbVHP overexpression led to higher vacuolar proton currents and vacuolar acidification. After 3 d in salt-untreated conditions, V-PPase-overexpressing leaves showed a drop in photosynthetic capacity, plasma membrane depolarization and eventual leaf necrosis. Salt, however, rescued NbVHP-hyperactive cells from cell death. Furthermore, a salt-induced rise in V-PPase but not of V-ATPase pump currents was detected in nontransformed plants. The results indicate that under normal growth conditions, plants need to regulate the V-PPase pump activity to avoid hyperactivity and its negative feedback on cell viability. Nonetheless, V-PPase proton pump function becomes increasingly important under salt stress for generating the pH gradient necessary for vacuolar proton-coupled Na+ sequestration.

Item Type:	Article
Authors/Creators:	Graus, D and Konrad, KR and Bemm, F and Patir Nebioglu, MG and Lorey, C and Duscha, K and Guthoff, T and Herrmann, J and Ferjani, A and Cuin, TA and Roelfsema, MRG and Schumacher, K and Neuhaus, HE and Marten, I and Hedrich, R
Keywords:	cell death, plasma membrane voltage, proton pump currents, salt, vacuolar pH, vacuolar proton-ATPase (V-ATPase), vacuolar proton-pyrophosphatase (V-PPase)
Journal or Publication Title:	New Phytologist
Publisher:	Wiley-Blackwell Publishing Ltd.
ISSN:	1469-8137
DOI / ID Number:	https://doi.org/10.1111/nph.15280
Copyright Information:	Copyright 2018 The AuthorsNew Phytologist Copyright 2018 New Phytologist Trust
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