SOS1 transporter of Physcomitrella patens mediates sodium efflux in planta

• Published in: The New phytologist 2010-11, Vol.188 (3), p.750-761
• Main Authors: Fraile‐Escanciano, Ana, Kamisugi, Yasuko, Cuming, Andrew C, Rodríguez‐Navarro, Alonso, Benito, Begoña
• Format: Article
• Language: English
• Subjects: Adenosine triphosphatases; Antiporters; Bryopsida - genetics; Bryopsida - metabolism; Cell death; Cell membranes; Cloning, Molecular; Complementary DNA; DNA, Complementary; Efflux; ENA ATPases; Fluxes; Gene deletion; Gene Targeting; Genes; Genes, Plant; Membrane vesicles; Mutants; Mutation; Na+ efflux; Na+/H+-exchanging ATPase; Physcomitrella patens; Plant cells; Plants; Polymerase chain reaction; Potassium; Salt-Tolerance - genetics; Sodium; Sodium - metabolism; sodium antiporter; Sodium Chloride - metabolism; Sodium-Hydrogen Exchangers - genetics; Sodium-Hydrogen Exchangers - metabolism; Sodium-Potassium-Exchanging ATPase - genetics; Sodium-Potassium-Exchanging ATPase - metabolism; SOS1; Stress, Physiological - genetics; Uptake; Yeast; Yeasts
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/j.1469-8137.2010.03405.x

• 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.