Yeast plasma membrane Ena1p ATPase alters alkali‐cation homeostasis and confers increased salt tolerance in tobacco cultured cells

Abstract In plants, the plasma membrane Na + /H + antiporter is the only key enzyme that extrudes cytosolic Na + and contributes to salt tolerance. But in fungi, the plasma membrane Na + /H + antiporter and Na + ‐ATPase are known to be key enzymes for salt tolerance. Saccharomyces cerevisiae Ena1p ATPase encoded by the ENA1/PMR2A gene is primarily responsible for Na + and Li + efflux across the plasma membrane during salt stress and for K + efflux at high pH and high K + . To test if the yeast ATPase would improve salt tolerance in plants, we expressed a triple hemagglutinin (HA)‐tagged Ena1p (Ena1p‐3HA) in cultured tobacco ( Nicotiana tabacum L.) cv Bright Yellow 2 (BY2) cells. The Ena1p‐3HA proteins were correctly localized to the plasma membrane of transgenic BY2 cells and conferred increased NaCl and LiCl tolerance to the cells. Under moderate salt stress conditions, the Ena1p‐3HA‐expressing BY2 clones accumulated lower levels of Na + and Li + than nonexpressing BY2 clones. Moreover, the Ena1p‐3HA expressing BY2 clones accumulated lower levels of K + than nonexpressing cells under no‐stress conditions. These results suggest that the yeast Ena1p can also function as an alkali‐cation (Na + , Li + , and K + ) ATPase and alter alkali‐cation homeostasis in plant cells. We conclude that, even with K + ‐ATPase activity, Na + ‐ATPase activity of the yeast Ena1p confers increased salt tolerance to plant cells during salt stress. © 2004 Wiley Periodicals, Inc.