Identification of Genome Specific Sequence Motifs in α-Gliadins and Wheat Accessions with Less Celiac Disease Epitopes

Among gliadins, α-gliadins are important active proteins in triggering celiac disease in human beings owing to the presence of toxic epitopes. A set of 177 α-gliadin gene sequences and the corresponding proteins were analyzed. Twenty accessions of hexaploids including 1, 14, and 5, respectively representing A, B, and D, with no intact CD-epitopes in α-gliadins, were identified. Twenty-two and 13 conserved motifs in non-repetitive domains NR1 and NR2, respectively, of α-gliadins differentiated all the amino acid sequences encoded by A genome of both diploids and hexaploids. Most of the amino acid sequences encoded by D genome (70 of 75 in hexaploids and 13 of 16 in diploids) could be identified by 22 amino acid motif. Large variations and lesser number of intact CD-epitopes was observed for α-gliadins belonging to B genome. As compared to diploids, repeat length of polyglutamine repetitive domain QII of B genome was lower in hexaploids indicating loss of Q residues during evolution of hexaploid wheat. The information can be used in assigning any α-gliadin sequences onto A, B, and D genomes and identifying wheat accessions with lesser CD-epitopes. The result presented here will be useful for the wheat improvement programs aiming for the management of celiac disease in human beings.