High-affinity potassium (K⁺) transporter (HAK)/K⁺ uptake permease (KUP)/K⁺ transporter (KT) have been identified in all genome-sequenced terrestrial plants. They play an important role in K+ acquisition and translocation and in enhancing salt tolerance. Here, we report that plasma-membrane-located OsHAK18 functions in K⁺ and sodium (Na⁺) circulation and sugar translocation in rice (Oryza sativa).

 

OsHAK18 was expressed mainly, though not exclusively, in vascular tissues and particularly in the phloem. Knockout (KO) of OsHAK18 reduced K⁺ concentration in phloem sap and roots but increased K⁺ accumulation in the shoot of both Nipponbare and Zhonghua11 cultivars, while overexpression (OX) of OsHAK18 driven by its endogenous promoter increased K⁺ concentration in phloem sap and roots and promoted Na⁺ retrieval from shoot to root under salt stress. Split-root experimental analysis of rubidium (Rb⁺) uptake and circulation indicated that OsHAK18-OX promoted Rb⁺ translocation from the shoot to the root.