Cloning,Construction RNAi Vector Of PtSKOR Genes And Expression Pattern Analysis Of Salt-tolerant Genes In Puccinellia Tenuiflora

Soil salinity is becoming a serious threat to the development of agricultural production in China.The alkali grass Puccinellia tenuiflora growing in the northeast and northwest of China is the member of the grass family which can resist salt stress extremely.Thus,we can study the mechanism of salt tolerance of Puccinellia tenuiflora to improve other crops.Our previous studies have shown that Puccinellia tenuiflora can resist the Na+ and uptake K+ to maintain the high K+/Na+ ratio to enhance the salt resistance.PtSOS1 was thought to be contributed to the high selectivity for K+ over Na+ in root,PtHKTI;5 was thought to be contributed to restrict Na+,PtNHX play an important role in adjusting the pH,but the relationship between them is unclear.In addition,the stelar K+ outward-rectifier channel SKOR expressed in the pericycle and xylem parenchyma cells,strongly contributes to K+ secretion into the xylem sap in order to maintain the high K+/Na+ ratio to resist salt stress through stabilizing the K+ content in shoot.In this study,we cloned the outward-rectifying potassium channel gene PtSKOR,and constructed its RNAi vector based on the establishment of tissue culture in order to explain the function of PtSKOR.Moreover,the accumulation of K+ and expression pattern of PtSKOR was analyzed under different KCl and NaCl treatment.We also analyzed the expression patterns of PtSOSl,PtHKT1;5 and PtNHX under different NaCl treatment to find their realationship.The main results as follows:1.PtSKOR gene of Puccinellia tenuiflora contains an ORF of 2148 bp encoding 715 amino acids,it may have six transmembrane segments(S1-S6),pore with highly conserved fragment TVGYG between S5 and S6,positively charged amino acids R in S4.The BLAST date showed PtSKOR shares above 56%homology with other outward-rectifying potassium channel.We also constructed its RNAi vector successfully.2.PtSKOR mainly expressed in the root,displaying strong transcription level to external K+,and the K+ concentration in shoot also increased.Furthermore,a significantly positive correlation was found between PtSKOR expression level in root and K+ content in shoot,we think that PtSKOR may contribute to K+ secrete into the xylem sap.3.The expression of PtSKOR was induced by 25 mM NaCl,and the concentration of K+ in shoot did not change significantly,suggesting that it may stabilize the K+ content when the grass is under salt treatment,and PtSKOR play an important role.4.PtHKT1;5 mainly expressed in root,PtNHX mainly expressed in shoot.The expression of PtSOSl,PtHKT1;5 and PtNHX was induced by salt treatment.5.Compared with the transcription level of PtHKT1;5,the relative expression level of PtSOSl at 6 h is more sharply with 578%under 25 mM NaCl treatment,suggesting that the PtSOSl may be playing a main role under mild salt treatment.It may contribute to Na+ secretion into the xylem sap or exclude Na+.6.Compared with the transc.ription level of PtSOSl,the relative expression level of PtHKT1;5 at 6 h is more sharply with 221%under 150 mM NaCl treatment,suggesting that the PtHKT1;5 may be playing a main role under severe salt treatment.It may contribute to recycle Na+ of xylem vascular into xylem parenchyma cells to mediate the homeostasis of Na+ between root and shoot.Above all,PtSKOR can contribute to K+ secrete into the xylem sap to stable the K+ content in shoot and improve high K+/Na+ ratio to resist the salt stress.Moreover,PtSOSl,PtHKT1;5 and PtNHX can work together to resist the salt stress.