Analysis of AtNHX1-expressing transgenic cotton under high salt conditions and in the field

Drought and salinity are two major limiting factors in crop productivity. To improve the salt tolerance in crops, one approach is to increase the solute concentration in the vacuoles of plant cells by sequestering sodium ion (Na+) into the vacuoles of plant cells. Consequently, it would reduce the toxicity of high Na+ in the cytoplasm and increase the vacuolar osmotic pressure with the concomitant generation of more negative water potential that favors water uptake by the cell and better tissue water retention under high soil salinity. The success of this approach was demonstrated in several plants, where overexpression of the Arabidopsis gene AtNHX1 that encodes a vacuolar sodium/proton antiporter resulted in higher plant salt tolerance.
In an effort to improve drought and salt tolerance of cotton that are grown in the semi-arid land of America¡¯s Southwest, we introduced the Arabidopsis gene AtNHX1 into cotton by using the Agrobacterium-mediated transformation. The AtNHX1-expressing cotton plants produced more biomass and fibers when grown in the presence of 200 mM NaCl in greenhouse conditions. The increased fiber yield was likely due to better photosynthetic performance and higher nitrogen assimilation rate observed in the AtNHX1-expressing cotton plants as compared to wild-type cotton plants under saline conditions. Furthermore, the field-grown AtNHX1-expressing cotton plants produced more fibers (by 25%) with better quality, indicating that AtNHX1 can indeed be used for improving salt stress tolerance in cotton.