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.

Benjamin Dubois,Dominique Mingeot,Pierre Bertin

doi:10.1007/s11032-016-0569-5

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.

Highlights

Gluten is the result of denaturation of endosperm storage proteins called prolamins during the dough kneading.These prolamins are water-insoluble proteins found in the seeds of bread wheat (Triticum aestivum L. ssp.aestivum), spelt [Triticum aestivum ssp. spelta (L.)Thell.] and durum wheat [Triticum turgidum ssp. durum (Desf.) Husnot]
Prolamins are composed of monomeric gliadins and polymeric glutenins (Shewry and Halford 2002), which can be divided into high-molecular-weight glutenin subunits (HMW-GS) and low-molecular-weight glutenin subunits (LMW-GS)
We identified in the spelt sequences a high proportion (52.3 %) of α-gliadins from

Summary

Introduction

Gluten is the result of denaturation of endosperm storage proteins called prolamins during the dough kneading.These prolamins are water-insoluble proteins found in the seeds of bread wheat (Triticum aestivum L. ssp.aestivum), spelt [Triticum aestivum ssp. spelta (L.)Thell.] and durum wheat [Triticum turgidum ssp. durum (Desf.) Husnot]. Gluten is the result of denaturation of endosperm storage proteins called prolamins during the dough kneading. These prolamins are water-insoluble proteins found in the seeds of bread wheat Thell.] and durum wheat [Triticum turgidum ssp. Equivalent proteins are found in other cereals, such as barley and rye. Prolamins are composed of monomeric gliadins and polymeric glutenins (Shewry and Halford 2002), which can be divided into high-molecular-weight glutenin subunits (HMW-GS) and low-molecular-weight glutenin subunits (LMW-GS). Gliadins are classified into α/β-, γ- and ω-gliadins according to their electrophoretic mobility.

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