Molecular and functional analysis of a vacuolar Na+/H+ antiporter gene of Rosa hybrida

A vacuolar Na+/H+ antiporter gene was isolated from Rosa hybrida (RhNHX1). The amino acid sequence encoded by the RhNHX1 cDNA shows homology to that of the yeast NHX1. The cDNA contains 2080 nucleotides and an open reading frame of 1632 nucleotides that encodes a protein of 543 amino acids with a deduced molecular mass of 60,045 daltons. The deduced amino acid sequence of RhNHX1 is 74.1% identical to that of a vacuolar Na+/H+ antiporter of Arabidopsis thaliana, AtNHX1, and contains the consensus amiloride-binding domain. RhNHX1 suppressed the hygromycin-sensitive phenotype of the yeast nhx1 mutant. In addition, the expression of RhNHX1 in rose increased in the presence of NaCl. These results suggest that the product of RhNHX1 functions as a vacuolar Na+/H+ antiporter in rose plants.