Molecular diversity of α-gliadin expressed genes in genetically contrasted spelt (Triticum aestivum ssp. spelta) accessions and comparison with bread wheat (T. aestivum ssp. aestivum) and related diploid Triticum and Aegilops species

Abstract

The gluten proteins of cereals such as bread wheat (Triticum aestivum ssp. aestivum) and spelt (T. aestivum ssp. spelta) are responsible for celiac disease (CD). The α-gliadins constitute the most immunogenic class of gluten proteins as they include four main T-cell stimulatory epitopes that affect CD patients. Spelt has been less studied than bread wheat and could constitute a source of valuable diversity. The objective of this work was to study the genetic diversity of spelt α-gliadin transcripts and to compare it with those of bread wheat. Genotyping data from 85 spelt accessions obtained with 19 simple sequence repeat (SSR) markers were used to select 11 contrasted accessions, from which 446 full open reading frame α-gliadin genes were cloned and sequenced, which revealed a high allelic diversity. High variations among the accessions were highlighted, in terms of the proportion of α-gliadin sequences from each of the three genomes (A, B and D), and their composition in the four T-cell stimulatory epitopes. An accession from Tajikistan stood out, having a particularly high proportion of α-gliadins from the B genome and a low immunogenic content. Even if no clear separation between spelt and bread wheat sequences was shown, spelt α-gliadins displayed specific features concerning e.g. the frequencies of some amino acid substitutions. Given this observation and the variations in toxicity revealed in the spelt accessions in this study, the high genetic diversity held in spelt germplasm collections could be a valuable resource in the development of safer varieties for CD patients.Electronic supplementary materialThe online version of this article (doi:10.1007/s11032-016-0569-5) contains supplementary material, which is available to authorized users.

Development of TaqMan probes targeting the four major celiac disease epitopes found in α-gliadin sequences of spelt (Triticum aestivum ssp. spelta) and bread wheat (Triticum aestivum ssp. aestivum)

“…Each of these four epitopes can be displayed in its canonical form, which is toxic, but some amino acid substitutions or deletions can reduce or suppress antigenic properties, according to the allelic variant [ 27 ]. Interestingly, the epitope variants highlighted in bread wheat α-gliadin sequences by Mitea et al [ 27 ] were similar to those found in spelt accessions [ 16 ].The multigenic character of the α-gliadin family results in a very high allelic variability and leads, among other things, to high variations in the immunogenic content from one α-gliadin sequence to another. The exploitation of this variability to develop safe spelt or wheat cultivars will probably require the combination of classical breeding and molecular technologies [ 12 ], and tools to infer the presence of sequences coding for toxic epitopes are needed.…”

“…It is particularly interesting because of the high genetic diversity held in spelt germplasm collections [ 13 – 15 ]. Moreover, genetic variations in their immunogenic potential, their bread-making qualities and their content in proteins, lipids, micronutrients and fibers have been pointed out [ 13 , 16 – 19 ].…”

Improvement of the process of hydrothermal treatment and peeling of spelt wheat grain during cereal production

“…Considering these traditional foods in the diet, the diet may cause inconvenience for the patients. That is why selectionists do research and improve existing varieties in order to remove the corresponding allergens for spelt wheat to become valuable raw material [16].…”

Celiac Antigenicity of Ancient Wheat Species

“…Ancient tetraploid wheat species have also been analyzed in this manner, and studies have shown that ancient durum wheat species found in Italy are not celiac safe [7]. In recent studies by Dubois et al [8,9] and Escarnot et al [10], the celiac immunogenicity of spelt and hexaploid wheat was investigated where they found that there is large variation among different spelt accessions regarding their celiac reactivity. In these studies, various methods such as ELISA were used for the quantitative analysis of celiac epitopes.…”