Abstract
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.