Abstract:

AaNhaD, a gene isolated from the soda lake alkaliphile Alkalimonas amylolytica, encodes a Na⁺/H⁺ antiporter crucial for the bacterium’s resistance to salt/alkali stresses. However, it remains unknown whether this type of bacterial gene may be able to increase the tolerance of flowering plants to salt/alkali stresses. To investigate the use of extremophile genetic resources in higher plants, transgenic tobacco BY-2 cells and plants harboring AaNhaD were generated and their stress tolerance was evaluated. Ectopic expression of AaNhaD enhanced the salt tolerance of the transgenic BY-2 cells in a pH-dependent manner. Compared to wild-type controls, the transgenic cells exhibited increased Na⁺ concentrations and pH levels in the vacuoles. Subcellular localization analysis indicated that AaNhaD-GFP fusion proteins were primarily localized in the tonoplasts. Similar to the transgenic BY-2 cells, AaNhaD-overexpressing tobacco plants displayed enhanced stress tolerance when grown in saline-alkali soil. These results indicate that AaNhaD functions as a pH-dependent tonoplast Na⁺/H⁺ antiporter in plant cells, thus presenting a new avenue for the genetic improvement of salinity/alkalinity tolerance.

Zhong NQ, Han LB, Wu XM, Wang LL, Wang F, Ma YH, Xia GX (2012) Ectopic expression of a bacterium NhaD-type Na⁺/H⁺ antiporter leads to increased tolerance to combined salt/alkali stresses. J. Integr. Plant Biol. 54(6), 412–421.

Key words: Alkaliphiles Alkalimonas amylolytica, Na⁺/H⁺ antiporter, tobacco BY-2 cells, high salinity stress, alkaline