Cloning, characterization and expression of wheat EDR1 (enhanced disease resistance) gene

To investigate if there is an EDR1 pathway in wheat (Triticum aestivum L.), a pair of degenerate primers was designed according to the cDNAs of Arabidopsis thaliana EDR1 gene and its homologs were used to isolate EDR1 gene homologs from wheat. RT-PCR was conducted on the cDNA template synthesized with RNA of wheat leaves. A 627-bp cDNA fragment representing an EDR1 gene (named as TaEDR1) was isolated (GenBank accession number: AY743662). Subsequently, the 3050-bp full-length cDNA sequence of TaEDR1, which encodes a polypeptide consisting of 959 amino acid residues, was obtained by RACE technique. The amino acid sequence of TaEDR1 and that of barley (Hordeum vulgare) EDR1 (signed as HvEDR1) show 92% identity. There is a highly conserved catalytic domain of serine/threonine protein kinases in the C-terminus of TaEDR1. Because this protein has a putative nuclear localization motif, it probably functions in the nucleus. This study provides the first molecular biological evidence of the presence of an EDR1 homolog in common wheat. The transcription pattern of TaEDR1 was investigated in leaves after inoculation with Blumeria graminis (DC.) E.O. Speer f. sp. tritici Em. Marchal (Bgt) through semi-quantitative RT-PCR (semi-QRT-PCR). The result showed that the transcribing of TaEDR1 was enhanced by Bgt. The expression pattern of the TaEDR1 gene in different tissues showed that it expressed in leaves, stems, spikes and roots. This study suggests that the TaEDR1, a MAP kinase kinase kinase, may function in wheat defense responses.