Duan HR, Ma Q, Zhang JL, Hu J, Bao AK, Wei L, Wang Q, Luan S, Wang SM^※. The inward-rectifying K⁺ channel SsAKT1 is a candidate involved in K⁺ uptake in the halophyte Suaeda salsa under saline condition. Plant and Soil. 2015. Doi: 10.1007/S11104-015-2539-9. http://www.springer.com/-/1/AU3p3lO7xIV6JZQW5JZu

摘要：

Background and aims The Shaker AKT1-like channels are considered to be involved in both high- and low-affinity K⁺ uptake and correlated with salt tolerance in glycophytes. Suaeda salsa (Suaeda maritima subsp. salsa), as a typical salt-accumulating halophyte, is able to absorb K⁺ efficiently while growing under saline conditions and taking in a large amount of Na⁺, thus maintaining the K⁺ concentration in its cells. In this study, the possible functions of the inward-rectifying K⁺ channel SsAKT1 in K⁺ uptake and salt tolerance in the halophyte S. salsa were investigated.

Methods SsAKT1 from S. salsa was isolated by RT-PCR and characterized using yeast complementation; the responses of SsAKT1 to various KCl and NaCl treatments were investigated by real-time quantitative PCR.

Results SsAKT1 consisted of 879 amino acid residues and shared high homology (60-67 %) with the identified inward-rectifying K⁺ channels AKT1 from other plants. The expression of SsAKT1 rescued the K⁺-uptake-defective phenotype of yeast strain CY162, and also suppressed the salt-sensitive phenotype of yeast strain G19, suggesting SsAKT1 functioned as an inward-rectifying K⁺ channel. SsAKT1 was predominantly expressed in roots, and was induced significantly by K⁺ starvation; transcript levels increased further on resupply of K⁺ (0.1-10 mM for 6 h) by 64 % in 0.1 mM K⁺ and 138-186 % in higher K⁺ concentrations (1-10 mM). Interestingly, the expression level of SsAKT1 in roots was also induced significantly by short-term treatment (6 h) with NaCl concentrations (25-250 mM).

Conclusions These results demonstrate that the inward-rectifying K⁺ channel SsAKT1 might mediate both high- and low-affinity K⁺ uptake in S. salsa, but play a greater role in the low-affinity system. Furthermore, SsAKT1 might also be involved in salt tolerance by participating in the maintenance of K⁺ nutrition in S. salsa under salinity.