Diversité génétique des céréales,recherche et caractérisation de leurs allergénes par l'approche protéomique

Abstract

In the first part of this study, two collections of wheat and one collection of triticale cultivated are analyzed to assess the genetic polymorphism of HMW-GS and SG-FPM: a collection of 69 triticale grown in France, another collection of 856 accessions of local durum wheat collected in Algeria and a priori divided into 17 botanical varieties according to their morphological characteristics, and the last two collections of 40 and 30 varieties of bread and durum wheats from Algerian oases. Biochemical analysis was performed by SDS-PAGE. In hexaploid triticale collection, allele nomenclature was compiled with a total of 36 alleles expressed at seven loci Glu-A1, Glu-B1, Glu-R1, Gli-R2, B2-Glu, Glu-A3, Glu- B3. This diversity has highlighted two major groups of triticale: winter and spring triticales. Important variation was found in the collection of botanic durum wheat. Among the 16 alleles identified at the Glu-1 loci, two were new. The first named Glu-B1i1 encoding for two bands located between 17 and 18 which was assigned the nomenclature 171 and 181. The other named Glu-B1e1 codes two bands similar to 20x and 20y but with faster mobility, which were named 20x1-20y1. At Glu-3 and Glu-2 loci, 19 alleles were identified, where the allele named Glu-B3ab (encoding for subunits 2-8-9-13-16) was considered as new. Analysis of Saharan wheats has identified a total of 32 and 29alleles for bread and durum wheat, respectively, which in combination resulted in 36 and 29 different patterns respectively. In bread wheat 3, 9 (including 1 new) and 4 alleles were observed at Glu-A1, Glu-B1 and Glu-D1 loci encoding HMW-GS respectively. LMW-GS displayed similar polymorphism, as 4, 9 and 3 alleles were identified at loci Glu-A3, Glu-B3 and Glu-D3 respectively. In durum wheat collection, 3 alleles were expressed at Glu-A1 locus and 9 (including 1 new) at Glu-B1. At Glu-A3, Glu-B3 and Glu-B2 loci 7, 8 (including 1 new) and 2 alleles were identified. Knowledge of these alleles is an important one hand to estimate the genetic variability and varietal identification and secondly in the selection for grain quality. Another part of this study aimed to characterize the major allergens of wheat and / or cereals, to break down the specific IgE response to evaluate the role of different protein families in the allergenicity of wheat. The analysis included 10 varieties and 14 sera from allergic Algerian and French patients to wheat. All biochemical and immunological analysis showed that all proteins are recognized by patients regardless of clinical grade observed. 90% of the sera reacted fraction to albumins / globulins fraction in immunoblotting. IgE sera recognize more than one wheat protein and results can be observed that the immunoreactivity varies with genotypes. And the antigenic profile that emerges from these results is composed of five major antigens, albumins / globulins, /,  and  gliadins and glutenins subunits low molecular weight and a minor antigen subunits of glutenin high molecular weight. It is difficult to conclude on the type of sensitization to one or more common epitopes of these patients. Four protein bands were identified by proteomic analysis. Confronted by mass spectrometry analysis LC-MS/MS, we can suggest the existence of thirteen wheat allergens in the four groups analyzed.