title: The SOS1 transporter of Physcomitrella patens mediates sodium efflux in planta.
abstract: • SOS1 is an Na(+)/H(+) antiporter that plays a central role in Na(+) tolerance in land plants. SOS1 mediation of Na(+) efflux has been studied in plasma-membrane vesicles and deduced from the SOS1 suppression of the Na(+) sensitivity of yeast mutants defective in Na(+) -efflux. However, SOS1-mediated Na(+) efflux has not been characterized in either plant or yeast cells. Here, we use Physcomitrella patens to investigate the function of SOS1 in planta. • In P. patens, a nonvascular plant in which the study of ion cellular fluxes is technically simple, the existence of two SOS1 genes suggests that the Na(+) efflux remaining after the deletion of the ENA1 ATPase is mediated by a SOS1 system. Therefore, we cloned the P. patens SOS1 and SOS1B genes (PpSOS1 and PpSOS1B, respectively) and complementary DNAs, and constructed the PpΔsos1 and PpΔena1/PpΔsos1 deletion lines by gene targeting. • Comparison of wild-type, and PpΔsos1 and PpΔena1/PpΔsos1 mutant lines revealed that PpSOS1 is crucial for Na(+) efflux and that the PpΔsos1 line, and especially the PpΔena1/PpΔsos1 lines, showed excessive Na(+) accumulation and Na(+)-triggered cell death. The PpΔsos1 and PpΔena1/PpΔsos1 lines showed impaired high-affinity K(+) uptake. • Our data support the hypothesis that PpSOS1 mediates cellular Na(+) efflux and that PpSOS1 enhances K(+) uptake by an indirect effect.
authors.affiliation: Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid, Madrid, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Fraile-Escanciano
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Kamisugi
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Cuming
authors.forename: Alonso
authors.initials: A
authors.lastname: Rodríguez-Navarro
authors.forename: Begoña
authors.initials: B
authors.lastname: Benito
mesh_terms: D019068:Bryopsida / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D018076:DNA, Complementary; D018390:Gene Targeting; D017343:Genes, Plant; D009154:Mutation; D055049:Salt Tolerance / Q000235:genetics*; D012964:Sodium / Q000378:metabolism*; D012965:Sodium Chloride / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics / Q000378:metabolism; D013312:Stress, Physiological / Q000235:genetics*
chemical_list: D018076:DNA, Complementary; D017923:Sodium-Hydrogen Exchangers; D012965:Sodium Chloride; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase