The role of OsHAK5 in potassium acquisition and transport from roots to shoots in rice at low potassium supply levels.

Plant physiology

PubMedID: 25157029

Yang T, Zhang S, Hu Y, Wu F, Hu Q, Chen G, Cai J, Wu T, Moran N, Yu L, Xu G. The role of OsHAK5 in potassium acquisition and transport from roots to shoots in rice at low potassium supply levels. Plant Physiol. 2014;.
In plants, KT/HAK/KUP is the largest potassium (K) transporter family, however, few of the members have had their physiological functions characterized in planta. Here we studied OsHAK5 of the KT/HAK/KUP family in rice. We determined its cellular and tissue localization, and analyzed its functions in rice using both OsHAK5 knockout mutants and overexpression lines at three genetic backgrounds. GUS reporter driven by OsHAK5 native promoter indicated OsHAK5 expression in various tissue organs from root to seed, abundantly in root epidermis and stele, the vascular tissues and mesophyll cells. Net K influx rate in roots and K transport from roots to aerial parts was severely impaired by OsHAK5 knockout but increased by OsHAK5 overexpression in 0.1 and 0.3 mM K external solution. The contribution of OsHAK5 to K mobilization within the rice plant was confirmed further by the change of K concentration in the xylem sap and K distribution in the transgenic lines when K was removed completely from the external solution. Overexpression of OsHAK5 increased [K]/[Na] ratio in the shoots and salt stress tolerance (shoot growth), while knockout of OsHAK5 decreased [K]/[Na] ratio in the shoots resulting in sensitivity to salt stress. Taken together, these results demonstrate that OsHAK5 plays a major role in K acquisition by roots faced with low external K and in K upward transport from roots to shoots in K deficient rice plants.