Molecular Characterization Of Gliadin Genes And Low Molecular Weight Glutenin Genes From Tetraploid Wheats

Specific PCR primers for α-gliadins and LMW-GS were designed based on the highly conserved distal sequences of 5' and 3' ends of known genes. In this study, coding regions of α-gliadin and LMW-GS genes from Triticum dicoccoides, T. araraticum and T. timopheevi were isolated and characterized. The results were as follows:1. Four gliadin genes, designated as GliTd-1 (GenBank No. DQ140349), GliTd-2 (DQ140350). GliTd-3 (DQ140351) and GliTd-4 (DQ140352), were obtained from T. dicoccoides accession As842. Sequence length for GliTd-1 and GliTd-2 were 821 and 859bp, respectively, which were considered as pseudogenes by the definition of containing in-frame stop codons and small insertions/deletions leading to frameshift. GliTd-3 and GliTd-4 were both 861bp, and their deduced amino acid sequences were both 267 residues with a 19-residue putative signal peptide (absent from mature proteins). The estimated molecular weight for GliTd-3 and GliTd-4 were 30.85 and 30.87 kD, respectively. The four gliadin sequences were analyzed using BLAST in NCBI. It was found that the four cloned gliadin genes had the closest homology with a-gliadins, confirming the new sequences as a-gliadin gene sequences. Six cysteine residues were not randomly distributed, but conserved in the two unique domains. The repetitive motifs were different from known genes. Amino acid sequence before the position 60 could be assumed to be more toxic for coeliac patients. Codon usage for proline was biased and condons for glutamine in a-gliadin genes were non-randomly distributed.2. Three LMW-GS sequences were obtained by sequencing the positive clones from T. dicoccoides accession As842. The complete nucleotide sequence lengths of...