Abstract:

In halophytic plants, the high-affinity potassium transporter HKT gene family can selectively uptake K⁺ in the presence of toxic concentrations of Na⁺. This has so far not been well examined in glycophytic crops. Here, we report the characterization of SbHKT1;4, a member of the HKT gene family from Sorghum bicolor. Upon Na⁺ stress, SbHKT1;4 expression was more strongly upregulated in salt-tolerant sorghum accession, correlating with a better balanced Na⁺/K⁺ ratio and enhanced plant growth. Heterogeneous expression analyses in mutants of Saccharomyces cerevisiae and Arabidopsis thaliana indicated that overexpressing SbHKT1;4 resulted in hypersensitivity to Na⁺ stress, and such hypersensitivity could be alleviated with the supply of elevated levels of K⁺, implicating that SbHKT1;4 may mediate K⁺ uptake in the presence of excessive Na⁺. Further electrophysiological evidence demonstrated that SbHKT1;4 could transport Na⁺ and K⁺ when expressed in Xenopus laevis oocytes. The relevance of the finding that SbHKT1;4 functions to maintain optimal Na⁺/K⁺ balance under Na⁺ stress to the breeding of salt-tolerant glycophytic crops is discussed.

Wang TT, Ren ZJ, Liu ZQ, Feng X, Guo RQ, Li BG, Li LG, Jing HC (2014) SbHKT1;4, a member of the high‐affinity potassium transporter gene family from Sorghum bicolor, functions to maintain optimal Na⁺/K⁺ balance under Na⁺ stress. J Integr Plant Biol 56: 315–332. doi: 10.1111/jipb.12144

Key words: Sorghum bicolour, High affinity potassium transporter (HKT), Na⁺/K⁺ ratio, Na⁺ stress, Salt tolerance