Molecular cloning and functional characterization of MdNHX1 reveals its involvement in salt tolerance in apple calli and Arabidopsis

- MdNHX1 is a vacuolar-localized Na+/H+ exchanger.
- Ectopic expression of MdNHX1 in yeast mutant strain YDR456W rescued the sensitivity to salt stress.
- Overexpression of MdNHX1 significantly improved salt tolerance in apple calli and Arabidopsis.

Soil salinity is a major limited factor for apple production in saline-alkali land worldwide. Previous studies reported that sodium/proton exchangers (NHXs) play important roles in salt tolerance. Here, we isolated MdNHX1, a vacuole-localized Na+/H+ exchanger, from 'Gala' apple (Malus × domestica Borkh.). Ectopic expression of MdNHX1 in yeast mutant strain YDR456W subsequently rescued the sensitivity of salt stress. qPCR assay demonstrated that MdNHX1 was mainly expressed in the stems and flowers of apple; and it can be induced by NaCl and PEG, but not by KCl and mannitol. Finally, we found that overexpression of MdNHX1 significantly improved salt tolerance in apple calli and Arabidopsis. In a word, our findings provide converging evidence that MdNHX1 is involved in the regulation of salt tolerance in plants.