Improved salt tolerance in a wheat stay-green mutant tasg1

Salt stress inhibited the growth of both tasg1 and wild-type (WT) wheat seedlings, but the inhibition in tasg1 plants was relatively weaker than that of WT. Compared to the WT, the chlorophyll content, thylakoid membrane polypeptides, Hill reaction activity, actual photochemical efficiency of PSII (ΦPSII), and Mg2+- and Ca2+-ATPase activities were higher in tasg1 under salt stress. At the same time, the photosynthetic activity of the tasg1 was significantly higher than that of WT. In addition, tasg1 plants displayed relatively less accumulation of reactive oxygen species and oxidative damage accompanied by higher activity of some antioxidant enzymes, and the up-regulation of antioxidant genes further demonstrated the improvement of antioxidant activity in tasg1 under salt stress. Furthermore, tasg1 plants also showed relatively weaker Na+ fluorescence and lower Na+ content, but relatively higher content of K+ in their roots and shoots, and then, the roots of tasg1 plants enhanced net outward Na+ flux and a correspondingly increased net inward K+ flux during salt stress. This might be associated with the relatively higher activity of H+-ATPase in tasg1 plants. These results suggest that the improved antioxidant competence and Na+/K+ ion homeostasis play an important role in the enhanced salinity tolerance of tasg1 plants.