Molecular characterization of alpha-gliadin gene sequences in Indian wheat cultivars vis-A -vis celiac disease eliciting epitopes

摘要

alpha-Gliadin proteins of the wheat gluten form a multigene family encoded by genomic loci Gli-A2, Gli-B2 and Gli-D2 located on the homoeologous wheat chromosomes 6AS, 6BS, and 6DS, respectively which upon partial digestion elicits celiac disease (CD) in the genetically susceptible individuals. The present investigation was planned to study the variations in the amino acid sequence of the alpha-gliadin proteins and CD eliciting epitopes in the Indian wheat cultivars. Representative wheat varieties released and cultivated in India during the period 1905-2011 were selected for studying the alpha-gliadin genes by cloning and sequencing followed by in silico analysis of the gene sequences. A lot of variation for alpha-gliadin gene sequences especially in T cell stimulatory epitopes glia-alpha 9, glia-alpha 20, glia-alpha 2 and glia-alpha was observed in different wheat varieties. Modern varieties released during 1971-2011 had higher proportion of intact T-cell stimulatory epitopes. The old wheat varieties released in the period 1905-1970 on the other hand had large proportion of variant epitopes. We identified three wheat varieties namely C591, C273 and K78 having only variant epitopes at Gli-D2 and Gli-B2 and both intact and variant epitopes at Gli-A2. Identification of lower proportion of T-cell stimulatory epitopes in these three varieties is the first step towards developing a wheat variety less immunogenic for celiac disease patients. The gene sequences of the selected varieties have been submitted at NCBI with accession numbers GenBank KJ410473-KJ410488.