Overexpression ofENA1 from yeast increases salt tolerance inArabidopsis

In yeast, the plasma membrane Na+/H+ antiporter and Na+-ATPase are key enzymes for salt tolerance.Saccharomyces cerevisiae Na+-ATPase (Enalp ATPase) is encoded by theENA1/PMR2A gene; expression ofENA1 is tightly regulated by Na+ and depends on ambient pH. Although Enalp is active mainly at alkaline pH values inS. cerevisiae, no Na+-ATPase has been found in flowering plants. To test whether this yeast enzyme would improve salt tolerance in plants, we introducedENA1 intoArabidopsis (cv. Columbia) under the control of the cauliflower mosaic virus 35S promoter. Transformants were selected for their ability to grow on a medium containing kanamyin. Southern blot analyses confirmed thatENA1 was transferred into theArabidopsis genome and northern blot analyses showed thatENA1 was expressed in the transformants. Several transgenic homozygous lines and wild-type (WT) plants were evaluated for salt tolerance. No obvious morphological or developmental differences existed between the transgenic and WT plants in the absence of stress. However, overexpression ofENA1 inArabidopsis improved seed germination rates and salt tolerance in seedlings. Under saline conditions, transgenic plants accumulated a lower amount of Na+ than did the wild type, and fresh and dry weights of the former were higher. Other experiments revealed that expression ofENA1 promoted salt tolerance in transgenicArabidopsis under both acidic and alkaline conditions.