| Sumario: | Vacuolar H-ATPase (V-H-ATPase) has been proved to be of importance in maintenance of ion homeostasis inside plant cells under NaCl stress. In this study, the expression levels and salt-tolerate function of V-H-ATPase genes were investigated in the roots and leaves of a halotolerate peppermint ( Mentha × piperita L.) Keyuan-1 treated with different concentrations of NaCl. Results showed that the expressions of V-H-ATPase in the transcriptional, protein and activity levels were significantly enhanced in the halotolerate peppermint Keyuan-1 compared to the wild-type (WT) peppermint under 50, 100, and 150 mM NaCl treatment. Moreover, inhibition experiments exhibited that V-H-ATPase activity played vital roles in the salt tolerance of peppermint Keyuan-1 to 150 mM NaCl stress through increasing the vacuolar H pumping activity and Na compartmentalization capacity. Furthermore, results of Western blots showed that the activity of a mitogen-activated protein kinase (MAPK) was significantly increased under different concentrations of NaCl in the halotolerate peppermint Keyuan-1, which was much higher than that of WT peppermint. Further experiments with inhibitors suggested that this MAPK protein was responsible for the enhanced expression of V-H-ATPase in the halotolerate peppermint Keyuan-1. In response to NaCl stress, increase of cytoplasmic calcium concentration ([Ca]) occurred upstream of MAPK activation in the halotolerate peppermint Keyuan-1. In all, these findings demonstrated that increased V-H-ATPase activity was positively correlated with the enhanced salt tolerance in the halotolerate peppermint Keyuan-1, providing the theoretic basis for the further development and utilization of peppermint in saline areas.
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