Overexpression of a samphire high-affinity potassium transporter gene SbHKT1 enhances salt tolerance in transgenic cotton

Abstract

Under salt stress, the plants need to maintain a low Na+ concentration and Na+/K+ ratio in the cell cytoplasm to keep normal growth and development. High-affinity K+ transporter (HKT) genes are known to play an important role in regulating the transportation of Na+ and K+ in higher plants. However, reports on its potential role in conferring stress tolerance in cotton are rare. In a previous study, we isolated a potassium transporter SbHKT1 from halophyte Salicornia bigelovii. With the intention to assess whether the SbHKT1 gene would improve salt tolerance in cotton, cotton plants overexpressing SbHKT1 were generated by Agrobacterium-mediated transgenic technology. Overexpression of SbHKT1 in cotton increased germination rate and biomass as well as root systems compared with wild-type plants. Transgenic cotton had significantly higher K+ content, lower Na+ content, and lower Na+/K+ ratio than wild-type plants in leaves, stems and roots under salt stress. Moreover, there were significant higher activity of antioxidant enzymes including SOD, POD, and CAT and lower malondialdehyde content which means better cell membrane integrity in transgenic cotton compared to control plants. These results indicated that overexpressing SbHKT1 in cotton improved salt tolerance by increasing the capacity of K+ uptake, K+/Na+ homeostasis, and the scavenging of reactive oxygen species.