To investigate the molecular mechanism of the ion transport in Reaumuria trigyna,we cloned the full length cDNA of vacuolar membrane Na⁺/H⁺ antiporter gene(RtNHX1) with reverse transcription PCR and rapid amplification of cDNA ends technologies.The cDNA is 2 622 bp long,which contained a 1 662 bp open reading frame,a 509 bp 5′-UTR,and a 451 bp 3′-UTR.The cDNA encoded a protein with 553 amino acids and molecular weight of 60.91 kD.The protein was predicted to be composed of 12 transmembrane domains,was characterized as a hydrophobic protein,and showed high homology with the vacuolar membrane Na⁺/H⁺ antiporter(NHX1) in other plant species.Quantitative real-time analysis showed that the expression levels of RtNHX1 under different salt concentrations and time gradients,were up-regulated initially and then down-regulated.The expression of RtNHX1 under the stress of 100 mmol/L NaCl for 6 hours and 200 mmol/L NaCl were reached the highest,which were over or nearly 3-fold of the control,indicating that RtNHX1 participated in the salt stress response of R.trigyna and may be an important element that plays a role in the ion transporting system in this plant.