Isolation and Analysis of α-Gliadin Gene Coding Sequences from Triticum durum

Three coding sequences of gliadins genes, designed as Gli2_Du1, Gli2_Du2 and Gli2_Du3, were isolated from the genomic DNA of Triticum durum accessions CItr5083. Gli2_Du1 and Gli2_Du2 contain 945 and 864 bp, encoding the mature proteins with 314 and 287 amino acid residues, respectively. Gli2_Du3 is recognized as a pseudogene due to the stop codon occurring in the coding region. The pseudogenes, commonly occurring in gliadins family, are attributed to the single base change C → T. The amino acid sequences deduced from these gene sequences were characterized with the typical structure of α-gliadin proteins, including the toxic sequences (PSQQQP). The peptide fraction PF(Y)PP(Q) is thought to be an extra unit of repetitive domain, slightly diverging from the previous report. Six cysteine residues were observed within two unique domains. Phylogenetic analysis showed Gli2_Du2 and Gli2_Du3 were closely related to the genes on chromosome 6A, whereas Gli2_Du1 seems to be more homologous with the genes on chromosome 6B.