Abstract: The full-length cDNA of the wheat (Triticum aestivum L.) root hair defective 3 gene (RHD3) has been cloned from the salt-tolerant hybrid wheat variety Shanrong No. 3 (Za3) using the mRNA differential display and 5'' rapid amplification of cDNA ends (RACE) methods. Analysis of the amino acid sequence deduced from the wheat RHD3 gene shows that two conservative GTP-binding motifs, namely GXXXXGKS and DXXG, in eukaryotes also exist at the N-terminal of wheat RHD3. In addition, an 18 amino acid residue transmembrane domain, namely FYLAVMFVVFLVGKAIWV, exists at positions 701–718 of the C-terminal of the deduced protein of wheat RHD3 obtained, but this domain is absent in another three proteins aligned, including rice RHD3, Arabidopsis RHD3, and yeast homologue SEY1. Northern blot revealed that transcription of the wheat RHD3 gene is down-regulated in both the salt-tolerant line and in JN177 under saline stress. A possible stress-responsive mechanism for this gene is discussed.

Key words: GTP-binding protein, root hair defective 3 gene (RHD3), salt stress, wheat salt-tolerant somatic hybrid.