Cloning of nine γ-gliadin mRNAs (cDNAs) from wheat and the molecular characterization of comparative transcript levels of γ-gliadin subclasses

Nine new full-length cDNA sequences for γ-gliadins were generated from total mRNA from bread and durum wheat. The length of the open reading frames (ORFs) ranged from 720 to 936 bp, which corresponds to putative proteins of 239–311 amino acid residues, respectively. All nine sequences, reconstructed from phylogenetic data showed sequences similar to the γ-gliadins registered at GenBank. All known γ-gliadin sequences fall into four major groups in the tree constructed by the neighbour-joining method. Primer pairs were designed to discriminate between these four γ-gliadin groups during grain development in bread wheat using quantitative real time polymerase chain reaction (QRT-PCR). Expression profiles of two lines of bread wheat showed higher levels of gene transcription for γ-gliadins from group II, whereas γ-gliadins from group I were expressed at the lowest level. Thus, the γ-gliadins from group II are expressed four- and 10-fold higher in ‘Perico’ and ‘Anza’, respectively, than the other γ-gliadins. The results reported may help to understand the order of synthesis and deposition of γ-gliadins in the grain of developing bread wheat. In addition, the differences found in the expression levels among the four groups could be used to select genotypes with specific profiles of γ-gliadins. These findings will also facilitate the up- and down-regulation of γ-gliadin gene expression in transgenic wheat.