Over-expression of a plasma membrane H+-ATPase SpAHA1 conferred salt tolerance to transgenic Arabidopsis

The SpAHA1 gene, encoding a plasma membrane (PM) H+-ATPase (AHA) in Sesuvium portulacastrum, was transformed into Arabidopsis plants, and its expression increased salinity tolerance of transgenic Arabidopsis plants: seed germination ratio, root growth, and biomass of transgenic plants were greater compared to wild-type plants under NaCl treatment condition. Upon salinity stress, both Na+ and H+ effluxes in the roots of SpAHA1 expressing plants were faster than those of untransformed plants. Transformed plants with SpAHA1 had lower Na+ and higher K+ contents relative to wild-type plants when treated with NaCl, resulting in greater K+/Na+ ratio in transgenic plants than in wild-type plants under salt stress. Extent of oxidative stress increased in both transgenic and wild-type plants exposed to salinity stress, but overexpression of SpAHA1 could alleviate the accumulation of hydrogen peroxide (H2O2) induced by NaCl treatment in transgenic plants relative to wild-type plants; the content of malondialdehyde (MDA) was lower in transgenic plants than that in wild-type plants under salinity stress. These results suggest that the higher H+-pumping activity generated by SpAHA1 improved the growth of transgenic plants via regulating ion and reactive oxygen species (ROS) homeostasis in plant cells under salinity stress.