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Molecular and Cellular Biology, November 2007, p. 7781-7790, Vol. 27, No. 22
0270-7306/07/$08.00+0     doi:10.1128/MCB.00430-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

SOS2 Promotes Salt Tolerance in Part by Interacting with the Vacuolar H⁺-ATPase and Upregulating Its Transport Activity

Giorgia Batelli,^1,2 Paul E. Verslues,¹ Fernanda Agius,¹ Quansheng Qiu,^3, Hiroaki Fujii,¹ Songqin Pan,¹ Karen S. Schumaker,³ Stefania Grillo,² and Jian-Kang Zhu^1*

Institute for Integrative Genome Biology and Department of Botany and Plant Sciences, University of California, Riverside, California 92521,¹ CNR-IGV Institute of Plant Genetics and Department of Soil, Plant, Environmental and Animal Production Sciences, University of Naples Federico II, 80055 Portici, Italy,² Department of Plant Sciences, University of Arizona, Tucson, Arizona 85721³

Received 13 March 2007/ Returned for modification 23 May 2007/ Accepted 28 August 2007

The salt overly sensitive (SOS) pathway is critical for plant salt stress tolerance and has a key role in regulating ion transport under salt stress. To further investigate salt tolerance factors regulated by the SOS pathway, we expressed an N-terminal fusion of the improved tandem affinity purification tag to SOS2 (NTAP-SOS2) in sos2-2 mutant plants. Expression of NTAP-SOS2 rescued the salt tolerance defect of sos2-2 plants, indicating that the fusion protein was functional in vivo. Tandem affinity purification of NTAP-SOS2-containing protein complexes and subsequent liquid chromatography-tandem mass spectrometry analysis indicated that subunits A, B, C, E, and G of the peripheral cytoplasmic domain of the vacuolar H⁺-ATPase (V-ATPase) were present in a SOS2-containing protein complex. Parallel purification of samples from control and salt-stressed NTAP-SOS2/sos2-2 plants demonstrated that each of these V-ATPase subunits was more abundant in NTAP-SOS2 complexes isolated from salt-stressed plants, suggesting that the interaction may be enhanced by salt stress. Yeast two-hybrid analysis showed that SOS2 interacted directly with V-ATPase regulatory subunits B1 and B2. The importance of the SOS2 interaction with the V-ATPase was shown at the cellular level by reduced H⁺ transport activity of tonoplast vesicles isolated from sos2-2 cells relative to vesicles from wild-type cells. In addition, seedlings of the det3 mutant, which has reduced V-ATPase activity, were found to be severely salt sensitive. Our results suggest that regulation of V-ATPase activity is an additional key function of SOS2 in coordinating changes in ion transport during salt stress and in promoting salt tolerance.

Published ahead of print on 17 September 2007.

Present address: Department of Plant Biology, University of Illinois, Urbana, IL 61801.

This article has been cited by other articles:

• Verslues, P. E., Batelli, G., Grillo, S., Agius, F., Kim, Y.-S., Zhu, J., Agarwal, M., Katiyar-Agarwal, S., Zhu, J.-K. (2007). Interaction of SOS2 with Nucleoside Diphosphate Kinase 2 and Catalases Reveals a Point of Connection between Salt Stress and H2O2 Signaling in Arabidopsis thaliana. Mol. Cell. Biol. 27: 7771-7780 [Abstract] [Full Text]