title: Ectopic expression of a bacterium NhaD-type Na+/H+ antiporter leads to increased tolerance to combined salt/alkali stresses.
abstract: AaNhaD, a gene isolated from the soda lake alkaliphile Alkalimonas amylolytica, encodes a Na(+) /H(+)  antiporter crucial for the bacterium's resistance to salt/alkali stresses. However, it remains unknown whether this type of bacterial gene may be able to increase the tolerance of flowering plants to salt/alkali stresses. To investigate the use of extremophile genetic resources in higher plants, transgenic tobacco BY-2 cells and plants harboring AaNhaD were generated and their stress tolerance was evaluated. Ectopic expression of AaNhaD enhanced the salt tolerance of the transgenic BY-2 cells in a pH-dependent manner. Compared to wild-type controls, the transgenic cells exhibited increased Na(+)  concentrations and pH levels in the vacuoles. Subcellular localization analysis indicated that AaNhaD-GFP fusion proteins were primarily localized in the tonoplasts. Similar to the transgenic BY-2 cells, AaNhaD-overexpressing tobacco plants displayed enhanced stress tolerance when grown in saline-alkali soil. These results indicate that AaNhaD functions as a pH-dependent tonoplast Na(+) /H(+)  antiporter in plant cells, thus presenting a new avenue for the genetic improvement of salinity/alkalinity tolerance.
authors.affiliation: Institute of Microbiology, Chinese Academy of Sciences, Beijing.
authors.forename: Nai-Qin
authors.initials: NQ
authors.lastname: Zhong
authors.forename: Li-Bo
authors.initials: LB
authors.lastname: Han
authors.forename: Xiao-Min
authors.initials: XM
authors.lastname: Wu
authors.forename: Li-Li
authors.initials: LL
authors.lastname: Wang
authors.forename: Fang
authors.initials: F
authors.lastname: Wang
authors.forename: Yan-He
authors.initials: YH
authors.lastname: Ma
authors.forename: Gui-Xian
authors.initials: GX
authors.lastname: Xia
mesh_terms: D002460:Cell Line; D003600:Cytosol / Q000378:metabolism; D020563:Gammaproteobacteria / Q000235:genetics*; D006863:Hydrogen-Ion Concentration; D030821:Plants, Genetically Modified / Q000378:metabolism*; D055049:Salt Tolerance / Q000235:genetics*; D012964:Sodium / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics* / Q000378:metabolism; D014026:Nicotiana / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism
chemical_list: D017923:Sodium-Hydrogen Exchangers; D012964:Sodium