Cloning And Expression Of A K~+Channel Gene SeAKT1from Salicornia Europaea

Potassium is an essential nutrient and the most abundant cation widely distribute in plant cells and organs, which participates in many vital physiological process in plants. A high and relatively stable potassium concentration in certain cell is important for plants. Potassium channels play a vital role in plants K+absorbtion. Although several potassium channel homologs in the AKT1subfamily (Shaker type) have been characterized from different plants, most of them come from glycophyte and sensitive to salt stress, little is known about the function of the potassium channels in euhalophyte. In this study, we aim at finding a Na+insensitive K+channel which can maintain K+uptake under salt stress, so we choose S.europaea, one of the most haloduric high terrestrial euhalophyte found in saline-alkali soil in north China, as our plant materials.In this study, a K+channel SeAKT1cDNA was isolated from S.europaea. The cDNA sequence of SeAKTl is3,189bp, which contained an open read frame of2,577bp encoding858amino acids. It was predicted that SeAKT1contained six trans-membrane domains (TM), named S1to S6; a cyclic nucleotide-binding domain (cNMP); a ankyrin domain at its C-terminal; and a KHA domain,which probable be involved in channel tetramerization or clustering in the membrane. SeAKTl is a typical Shaker type K+channel in plants. A phylogenetic analysis showed that SeAKT1belongs to the AKT1subfamily in the Shaker-like K+channel family.The express of SeAKT1in transcript level was up-regulated in response to K+starvation and it was also increased in response to both K+starvation and NaC1stresses in one-week-old or four-week-old seedlings. Furthermore, the transcript level of SeAKTl was up-regulated in response to100mM NaC1in one-week-old seedlings and down-regulated slightly in four-week-old seedlings when response to700mM NaC1. SeAKT1was expressed in both roots and shoots in four-week-old seedlings and was predominantly expressed in the roots than shoots.The coding region of SeAKT1was subcloned into the plant transformation binary vector pBI121. Arabidopsis (ecotype Columbia) was transformed by the floral dip method. Potassium exhaust experiment indicated that SeAKTl was a dual-affinity potassium channel. Under the condition of different stresses, transgene SeAKT1Arabidopsis can maintain a relatively higher K+/Na+by absorb more K+and less Na+in roots and shoots than control.