Identification of Arabidopsis mutants affected in K+ homeostasis

Abstract

Salinity is one of the environmental problems with greater impact on global food production, especially in semiarid areas such as the Mediterranean region. Previous work has shown that sodium uptake is counteracted by increased potassium transport or decreased H+ pumping and that mutants with the latter phenotypes can be obtained by screening for norspermidine (NE) resistance (Alejandro et al, 2007, EMBO J 26: 3203). This polycation enters the cell by some unidentified system strongly dependent on the electrical potential of the plasma membrane. As this biophysical parameter is determined by the relative activities of H+-ATPase and K+ transport, mutants tolerant to NE would be more tolerant to Na+and would allow us to identify regulators of H+ pumping and K+ influx. We have screened 100.000 mutant lines of Arabidopsis tagged with T-DNA (about 700.000 seeds) and obtained 40 mutants tolerant to this polycation, confirmed with germination percentages between 2 and 8 times greater than wild type.