title: Relationship between expression of the PM H+-ATPase, growth and ion partitioning in the leaves of salt-treated Medicago species.
abstract: The role of the plasma membrane (PM) H(+)-ATPase (E.C. 3.6.1.3) in the plant's response to salt stress was studied in the perennial leguminosae forage Medicago arborea L. and its close relative Medicago citrina (Font-Quer) Greuter, a species exposed to saline conditions in its original habitat. Plants were solution cultured for 8 days in 1 or 100 mM NaCl. Leaf growth and CO(2) assimilation were more inhibited by salt in M. arborea than in M. citrina. Both species were able to osmoregulate, and salt-treated plants maintained turgor potentials, with no differences between species. Contrasting ion distribution patterns showed that M. citrina was able to exclude Na(+) from the leaves more selectively, while M. arborea had a greater buildup of leaf blade Na(+). Isolation of purified PM and quantification of H(+)-ATPase protein by Western blot analysis against the 46E5B11D5 or AHA3 antibodies showed an increase in response to salt stress in the expanding (92%) and expanded leaves (87%) of M. citrina, while no differences were found in the corresponding leaves of M. arborea. The assay of H(+)-ATPase specific activity of the two leaf types in salinized M. citrina confirmed this increase, as activities increased with 55% and 104% for the expanded and expanding leaves, respectively, while no significant differences were found for either leaf type of salinized M. arborea. A possible role of the increased expression of the PM H(+)-ATPase for leaf expansion and ion exclusion in salt-stressed plants is discussed.
authors.affiliation: Departament de Biologia, Universitat de les Illes Balears, Cra. Valldemossa km 7.5., 07122 Palma de Mallorca, Spain. dbsjsi4@uib.es
authors.forename: John V
authors.initials: JV
authors.lastname: Sibole
authors.forename: Catalina
authors.initials: C
authors.lastname: Cabot
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Michalke
authors.forename: Charlotte
authors.initials: C
authors.lastname: Poschenrieder
authors.forename: Juan
authors.initials: J
authors.lastname: Barceló
mesh_terms: D002462:Cell Membrane / Q000201:enzymology*; D018506:Gene Expression Regulation, Plant; D017136:Ion Transport / Q000502:physiology*; D029902:Medicago / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D018515:Plant Leaves / Q000201:enzymology / Q000254:growth & development; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D012965:Sodium Chloride / Q000494:pharmacology*; D014867:Water / Q000378:metabolism
chemical_list: D014867:Water; D012965:Sodium Chloride; D006180:Proton-Translocating ATPases