Soil salinity causes negative effects on the growth and yield of crops. In this study, two sweet potato (Ipomoea batatas. L) cultivars, Xushu 28 (X-28) and Okinawa 100 (O-100), were examined under 50 and 100 mmol L -1 NaCl stress. X-28 cultivar is relatively high salt tolerant than O-100 cultivar. Interestingly, real-time quantitative polymerase chain reaction (RT-qPCR) results indicated that sweet potato high-affinity K + transporter 1 (IbHKT1) gene expression was highly induced by 50 and 100

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... mol L -1 NaCl stress in the stems of X-28 cultivar than in those of O-100 cultivar, but only slightly induced by these stresses in the leaves and fibrous roots in both cultivars. To characterize the function of IbHKT1 transporter, we performed ion-flux analysis in tobacco transient system and yeast complementation. Tobacco transient assay showed that IbHKT1 could uptake sodium (Na + ). Yeast complementation assay showed that IbHKT1 could take up K + in 50 mmol L -1 K + medium without the presence of NaCl. Moreover, Na + uptake significantly increased in yeast overexpressing IbHKT1. These results showed that IbHKT1 transporter could have K + -Na + symport function in yeast. Therefore, the modes of action of IbHKT1 in transgenic yeast could differ from the mode of action of the other class I HKT1 transporters. Potentially, IbHKT1 could be used to improve the salt tolerance nature in sweet potato.