LAUSR

In plants under hypersaline stress, the main transporter that extrudes sodium ions (Na + ) is the Na + /H + antiporter SOS1. Different from land plants, the intertidal macroalgae, Neopyropia/Neoporphyra contains an animal-type Na + /K + -ATPase as well as the SOS1 system. However, the contribution of Na + /K + -ATPase to the K + /Na + homeostasis of intertidal macroalgae remains unclear. In this study, we analyzed the function of Na + /K + -ATPase in the response of Neoporphyra haitanensis to salt stress from the perspective of ion transport dynamics. Both the transcript level of NhNKA2 and enzyme activity of Na + /K + -ATPase increased in the early response of N. haitanensis thalli to hypersaline stress. Addition of ouabain, an inhibitor of Na + /K + -ATPase, resulted in Na + accumulation in the cells, severe K + leakage from the thalli, and then remarkably disturbed the K + /Na + homeostasis in N. haitanensis thalli. This disruption might induce a significant decrease in photosynthesis and a severe oxidative damage in thalli. Accordingly, these results suggested that the important role of Na + /K + -ATPase in the resistance of intertidal macroalgae to hypersaline stress, and shed light on the diversity of K + /Na + homeostasis maintenance mechanisms in plants.