Mitteilungen der Gesellschaft für Pflanzenbauwissenschaften Band 23

Mitt. Ges. Pflanzenbauwiss. 23: 190 (2011)
Effect of salt stress on vacuolar Na + /H + antiporter activity in maize
hybrid SR05 during the second phase
Abdel-Kareem Mohamed, Stefan Hanstein, Britta Pitann and Sven Schubert
Institute of Plant Nutrition, Justus-Liebig-University, Gießen. E-Mail: Abdel.k.Mohamed@ernaehrung
.uni-giessen.de
Hypothesis
Salinity limits plant growth and impairs plant productivity. In order to overcome these
limitations, plants have evolved different strategies to improve resistance against
high Na + concentrations. At the cellular level, Na + compartmentation into vacuoles
provides an efficient mechanism to maintain Na + at non-toxic concentrations in the
cytosol (Sottosanto et al., 2007). The transport of Na + into the vacuole is mediated by
an Na + /H + antiporter (NHX) that is driven by the electrochemical proton gradient
generated by the H + -ATPase and H + -PPase (Blumwald, 2000). The aim of this work
was to investigate the effect of salt stress on NHX activity in the newly developed
maize hybrid SR 05 that shows improved salt resistance (Schubert et al. 2009).
Results and Discussion
Tonoplast vesicles were isolated from young leaves (Queiros et al., 2009) of Zea
mays L. genotype SR 05 grown under control (1 mM NaCl) and saline conditions
(200 mM NaCl). The proton pumping activity across tonoplast vesicles was
measured as the initial rate of fluorescence quenching of 9-amino-6-chloro-2methoxyacridine
(ACMA) after adding Mg-ATP. In order to describe NHX activity,
pumping activity of tonoplast H + -ATPase and maximum pH gradient in the absence
and in the presence of Na + were compared.
Addition of Na + to the pumping assay significantly decreased the pH gradient in
vesicles of salt-treated plants by 51% (n = 3). This strongly indicates that Na + /H +
antiporters were operating in vesicles from salt-treated plants. In control plants
addition of Na + to the pumping assay decreased the pH gradient by 38%, which was
not significant. The findings support the hypothesis that salt stress increases the
activity of tonoplast Na + /H + antiporters in leaves of the salt-resistant maize genotype
SR 05 and thus increases Na + transport from the cytoplasm to the vacuole.
References
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Queiros, F., Fontes, N., Silva, P., Almeida, D., Maeshima, M., Geros, H. and Fidalgo, F. 2009: Activity
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Schubert, S., Neubert, A., Schierholt, A., Sümer, A., Zörb, C. 2009: Development of salt-resistant
maize hybrids: The combination of physiological strategies using conventional breeding methods.
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Sottosanto, J.B., Saranga, Y., Blumwald, E. 2007: Impact of AtNHX1, a vacuolar Na + /H + antiporter,
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