Deletion of wheat alpha-gliadins from chromosome 6D improves gluten strength and reduces immunodominant celiac disease epitopes.

Abstract

Wheat gliadins and glutenins confer valuable end-use characteristics but include amino acid sequences (epitopes) that can elicit celiac disease (CeD) in genetically predisposed individuals. The onset of CeD in these individuals is affected by the amount and duration of the exposure to immunogenic epitopes. Therefore, a reduction of epitopes that result in high immune responses in the majority of CeD patients (immunodominant epitopes) may reduce the incidence of CeD at a population level. We generated gamma radiation-induced deletions encompassing the α-gliadins in each of the three wheat genomes and characterized them using exome capture. These deletions, designated as Δgli-A2, Δgli-B2, and Δgli-D2, were deposited in GRIN-Global. The Δgli-A2 and Δgli-B2 deletions showed limited effects on breadmaking quality, but the Δgli-D2 deletion significantly increased gluten strength and improved breadmaking quality without compromising dough elasticity, protein content, or grain yield. The stronger effect of Δgli-D2 on gluten strength was associated with an increased proportion of glutenins and the deletion of α-gliadins with seven cysteines, which are absent in the GLI-A2 and GLI-B2 loci. We show that α-gliadins with seven cysteines are incorporated into the gluten polymer, where they likely function as chain terminators limiting the expansion of the gluten polymer and reducing its strength. In addition to its beneficial effects on breadmaking quality, the Δgli-D2 deletion eliminates major wheat immunodominant CeD epitopes. The deployment of this publicly available Δgli-D2 deletion can simultaneously improve wheat gluten strength and reduce the population-wide burden of CeD.