title: Vacuolar cation/H+ exchange, ion homeostasis, and leaf development are altered in a T-DNA insertional mutant of AtNHX1, the Arabidopsis vacuolar Na+/H+ antiporter.
abstract: The function of vacuolar Na+/H+ antiporter(s) in plants has been studied primarily in the context of salinity tolerance. By facilitating the accumulation of Na+ away from the cytosol, plant cells can avert ion toxicity and also utilize vacuolar Na+ as osmoticum to maintain turgor. As many genes encoding these antiporters have been cloned from salt-sensitive plants, it is likely that they function in some capacity other than salinity tolerance. The wide expression pattern of Arabidopsis thaliana sodium proton exchanger 1 (AtNHX1) in this study supports this hypothesis. Here, we report the isolation of a T-DNA insertional mutant of AtNHX1, a vacuolar Na+/H+ antiporter in Arabidopsis. Vacuoles isolated from leaves of the nhx1 plants had a much lower Na+/H+ and K+/H+ exchange activity. nhx1 plants also showed an altered leaf development, with reduction in the frequency of large epidermal cells and a reduction in overall leaf area compared to wild-type plants. The overexpression of AtNHX1 in the nhx1 background complemented these phenotypes. In the presence of NaCl, nhx1 seedling establishment was impaired. These results place AtNHX1 as the dominant K+ and Na+/H+ antiporter in leaf vacuoles in Arabidopsis and also suggest that its contribution to ion homeostasis is important for not only salinity tolerance but development as well.
authors.affiliation: Department of Pomology, University of California, One Shields Ave, Davis, CA 95616, USA.
authors.forename: Maris P
authors.initials: MP
authors.lastname: Apse
authors.forename: Jordan B
authors.initials: JB
authors.lastname: Sottosanto
authors.forename: Eduardo
authors.initials: E
authors.lastname: Blumwald
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics*; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D016254:Mutagenesis, Insertional; D019441:Plant Epidermis / Q000235:genetics / Q000502:physiology; D018515:Plant Leaves / Q000235:genetics / Q000502:physiology; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D027682:Cation Transport Proteins; D004269:DNA, Bacterial; C117751:NHX1 protein, Arabidopsis; D017923:Sodium-Hydrogen Exchangers; C036483:T-DNA