The K+/H+ antiporter AhNHX1 improved tobacco tolerance to NaCl stress by enhancing K+ retention

High salinity is the one of important factors limiting plant growth and crop production. Many NHX-type antiporters have been reported to catalyze K + /H + exchange to mediate salt stress. This study shows that an NHX gene from Arachis hypogaea L. has an important role in K + uptake and transport, which affects K + accumulation and plant salt tolerance. When overexpressing AhNHX1 , the growth of tobacco seedlings is improved with longer roots and a higher fresh weight than the wild type (WT) under NaCl treatment. Meanwhile, when exposed to NaCl stress, the transgenic seedlings had higher K + /H + antiporter activity and their roots got more K + uptake. NaCl stress could induce higher K + accumulation in the roots, stems, and leaves of transgenic tobacco seedlings but not Na + accumulation, thus, leading to a higher K + /Na + ratio in the transgenic seedlings. Additionally, the AKT1 , HAK1 , SKOR , and KEA genes, which are involved in K + uptake or transport, were induced by NaCl stress and kept higher expression levels in transgenic seedlings than in WT seedlings. The H + -ATPase and H + -PPase activities were also higher in transgenic seedlings than in the WT seedlings under NaCl stress. Simultaneously, overexpression of AhNHX1 increased the relative distribution of K + in the aerial parts of the seedlings under NaCl stress. These results showed that AhNHX1 catalyzed the K + /H + antiporter and enhanced tobacco tolerance to salt stress by increasing K + uptake and transport.