Unraveling the K+ transporter gene family in rice: evolution, subcellular localization, K+ uptake activity, and transcriptional responses to salt stress

Abstract

Rice is a global staple food crop, and its yield is seriously limited by soil salinity. The high-affinity K+ transporter/K+ uptake permease/K+ transporter (HAK/KUP/KT) family of potassium transporters plays a pivotal role in K+ homeostasis and plant salt tolerance. However, their systematic characterization and functional relevance to salt tolerance in rice have not been clarified. Here, we conducted genome-wide identification and structural characterization of the HAK/KUP/KT family, assessed their expression profiles under salt stress, and examined their K+ transport function. In total, 27 OsHAK genes were identified in the rice genome, most of which exhibited salt-responsive expression. Yeast functional complementation assays confirmed that OsHAK11, OsHAK13, OsHAK23, OsHAK24, OsHAK25, and OsHAK26 can mediate K+ absorption. Among them, OsHAK11 and OsHAK25 showed relatively strong K+ uptake ability. Subcellular localization analysis revealed that OsHAK11 and OsHAK25 were located in the plasma membrane. Our research systematically analyzed the sequence characteristics of the rice HAK gene family, examined their transcriptional responses to salt stress, and further evaluated the K+ uptake capacity of HAK proteins. These results provide a foundation for further elucidating the function of OsHAKs in plant salt tolerance.