title: SOS2 promotes salt tolerance in part by interacting with the vacuolar H+-ATPase and upregulating its transport activity.
abstract: 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.
authors: Institute for Integrative Genome Biology and Department of Botany and Plant Sciences, University of California, Riverside, California 92521, USA.
authors: Giorgia
authors: G
authors: Batelli
authors: Paul E
authors: PE
authors: Verslues
authors: Fernanda
authors: F
authors: Agius
authors: Quansheng
authors: Q
authors: Qiu
authors: Hiroaki
authors: H
authors: Fujii
authors: Songqin
authors: S
authors: Pan
authors: Karen S
authors: KS
authors: Schumaker
authors: Stefania
authors: S
authors: Grillo
authors: Jian-Kang
authors: JK
authors: Zhu
mesh_terms: D017360:Arabidopsis / Q000033:anatomy & histology / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000502:physiology; D003681:Dehydration; D005838:Genotype; D010641:Phenotype; D030821:Plants, Genetically Modified; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012492:Salts / Q000378:metabolism*; D020798:Two-Hybrid System Techniques; D025262:Vacuolar Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D020033:Protein Isoforms; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; D012492:Salts; C406738:SOS2 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases; D025262:Vacuolar Proton-Translocating ATPases