Regulation of the non-selective Na importer capacity of NRT1.2/NPF4.6/AIT1 by SOS2-mediated phosphorylation in Arabidopsis.

Although preventing sodium ion import is crucial for salt tolerance, the mechanisms and the Na importers involved remain unclear. We identified NRT1.2/NPF4.6/AIT1 as a non-selective Na importer. NRT1.2 overexpression in Arabidopsis increased salt sensitivity due to Na accumulation, while nrt1.2 mutants exhibited opposite results. Non-invasive micro-test technology indicated Na uptake capability of NRT1.2 in Arabidopsis roots. When expressed in Xenopus laevis oocytes, NRT1.2 displayed low-pH-dependent and NO-promoted Na, K, and Li importer capacity, conferring higher potassium and lithium tolerance in NRT1.2 overexpression plants. Mechanically, salt overly sensitive 2 (SOS2) phosphorylated NRT1.2 at Thr248, reducing its Na import and preventing excessive Na accumulation. Prolonged salt stress also downregulated NRT1.2 transcripts. In summary, our findings unveil a role of NRT1.2 in Na transport and a regulatory pathway via SOS2-mediated phosphorylation of NRT1.2 at Thr248, crucial for plant salt-stress adaptation.