Rice shaker potassium channel OsAKT2 positively regulates salt tolerance and grain yield by mediating K + redistribution

Maintaining Na + /K + homeostasis is a critical feature for plant survival under salt stress, which depends on the operation of Na + and K + transporters. Although some K + transporters mediating root K + uptake have been reported to be essential to the maintenance of Na + /K + homeostasis, the effect of K + long‐distance translocation via phloem on plant salt tolerance remains unclear. Here, we provide physiological and genetic evidence of the involvement of phloem‐localized OsAKT2 in rice salt tolerance. OsAKT2 is a K + channel permeable to K + but not to Na + . Under salt stress, a T‐DNA knock‐out mutant, osakt2 and two CRISPR lines showed a more sensitive phenotype and higher Na + accumulation than wild type. They also contained more K + in shoots but less K + in roots, showing higher Na + /K + ratios. Disruption of OsAKT2 decreases K + concentration in phloem sap and inhibits shoot‐to‐root redistribution of K + . In addition, OsAKT2 also regulates the translocation of K + and sucrose from old leaves to young leaves, and affects grain shape and yield. These results indicate that OsAKT2‐mediated K + redistribution from shoots to roots contributes to maintenance of Na + /K + homeostasis and inhibition of root Na + uptake, providing novel insights into the roles of K + transporters in plant salt tolerance.