Na /K -ATPase regulates the K /Na homeostasis in the intertidal macroalgae, , in response to salt stress.

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, 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 to salt stress from the perspective of ion transport dynamics. Both the transcript level of and enzyme activity of Na /K -ATPase increased in the early response of 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 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.