Cloning And Functional Analysis Of The Potassium Transporters Genes RtHKT1 And RtKCO1 In Reaumuria Trigyna

Reaumuria trigyna is a recretohalophyte, a rare remnant derived from the mediterranean Sea. Is unique to the Eastern Alxa—Western Ordos area. R. trigyna has a remarkable capability to tolerate salinity and drought environment. In the transcriptome sequencing database, we found that ion homeostasis regulatory mechanism of R.trigyna played a pivotal role in response to salt stress. High-affinity potassium transporter HKT and Outward rectifying potassium channel KCO play a major function in the uptake, transportation of potassium and distribution in different tissues as well as maintenance of K+/Na+ homeostasis. In present research, RtHKT1 and RtKCO1 genes were isolated from R. trigyna the Gene expression profile were analyzed, and the function of these genes under the different ion stress conditions were studied. The results will help to understand the ion homeostasis regulatory mechanism to adaption saline environment of R. trigyna. The main results are as follow:1. High-affinity potassium transporter RtHKT1 and Outward rectifying K+ channel RtKCO1 were isolated based on the transcriptome database of R.trigyna. RtHKT1 contains a 1857bp open reading frame (ORF), encoding a protein with 619 amino acids. The ORF length of RtKCO1 is 1076bp, encoding a protein with 358 amino acids. RtHKT1 and RtKCO1 all localized the plasma membrance of cell.2. Gene expression profile analysis showed that RtHKT1 and RtKCO1 were expressed in root, stems and leaves, the expression in leaves was significantly higher than those in stems or roots. RtHKT1 displayed the similar expression patterns with RtKCO1 in NaCl treatments, mRNA levels were downregulated compared with controls. The expression levels of these genes under different salt concentrations were decreased firstly, then increased and further decreased. The expression of these genes under the stress of 200mM NaCl were reached the highest. Under the stress of KCl with different concentrations, the expression levels of RtHKTl was significantly increased by OmM-10mM KCl treatment, While the expression levels of RtKCO1 was significantly increased in 25mM-50mM KCl treatment. The result suggested that RtHKTl is a double-affinity potassium transporters and RtKCO1 is a low-affinity potassium channel.3. Heterogeneous expression analyses in AXT3 mutants of Saccharomyces cerevisiae indicated that the growth of yeast expressing RtHKT1 or RtKCO1 was obviouslv restored under different Na+ and K+ ion stress. The result indicated expression of RtHKT1 and RtKCO1 were obviously improved the salt stress and potassium ion stress tolerance of AXT3 yeast mutants.