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High V-PPase activity is beneficial under high salt loads, but detrimental without salinity

Graus, D, Konrad, KR, Bemm, F, Patir Nebioglu, MG, Lorey, C, Duscha, K, Guthoff, T, Herrmann, J, Ferjani, A, Cuin, TA, Roelfsema, MRG, Schumacher, K, Neuhaus, HE, Marten, I and Hedrich, R 2018 , 'High V-PPase activity is beneficial under high salt loads, but detrimental without salinity' , New Phytologist , pp. 1-12 , doi: 10.1111/nph.15280.

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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: 10.1111/nph.15280
Copyright Information:

Copyright 2018 The AuthorsNew Phytologist Copyright 2018 New Phytologist Trust

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