Molecular insights into maize Na⁺/H⁺ antiport

Abstract

We have developed a maize inbred line which shows efficient Na⁺ exclusion (Schubert, 1999, Fortmeier & Schubert, 1995). Using degenerate primers directed against the conserved motifs of known Na⁺/H⁺ antiporters, a fragment of the putative Na⁺/H⁺ antiporter was isolated and cloned from root material of Na⁺ excluding genotypes. This fragment of 320 bp contains the putative amiloride binding site. The sequence (ZmNHX1) was extended in a 5’ RACE experiment and accepted as genebank acc no. AF307944. Derived amino acid sequence analysis shows high homology (89.8%) to the rice OsNHX1 Na⁺/H⁺ exchanger. Regulation of the Na⁺/H⁺ antiporter gene was checked in a northern blot experiment using the cloned fragment as a probe.