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Towards reducing the immunogenic potential of wheat flour: omega gliadins encoded by the D genome of hexaploid wheat may also harbor epitopes for the serious food allergy WDEIA.

ABSTRACT: BACKGROUND:Omega-5 gliadins are a group of highly repetitive gluten proteins in wheat flour encoded on the 1B chromosome of hexaploid wheat. These proteins are the major sensitizing allergens in a severe form of food allergy called wheat-dependent exercise-induced anaphylaxis (WDEIA). The elimination of omega-5 gliadins from wheat flour through biotechnology or breeding approaches could reduce the immunogenic potential and adverse health effects of the flour. RESULTS:A mutant line missing low-molecular weight glutenin subunits encoded at the Glu-B3 locus was selected previously from a doubled haploid population generated from two Korean wheat cultivars. Analysis of flour from the mutant line by 2-dimensional gel electrophoresis coupled with tandem mass spectrometry revealed that the omega-5 gliadins and several gamma gliadins encoded by the closely linked Gli-B1 locus were also missing as a result of a deletion of at least 5.8 Mb of chromosome 1B. Two-dimensional immunoblot analysis of flour proteins using sera from WDEIA patients showed reduced IgE reactivity in the mutant relative to the parental lines due to the absence of the major omega-5 gliadins. However, two minor proteins showed strong reactivity to patient sera in both the parental and the mutant lines and also reacted with a monoclonal antibody against omega-5 gliadin. Analysis of the two minor reactive proteins by mass spectrometry revealed that both proteins correspond to omega-5 gliadin genes encoded on chromosome 1D that were thought previously to be pseudogenes. CONCLUSIONS:While breeding approaches can be used to reduce the levels of the highly immunogenic omega-5 gliadins in wheat flour, these approaches are complicated by the genetic linkage of different classes of gluten protein genes and the finding that omega-5 gliadins may be encoded on more than one chromosome. The work illustrates the importance of detailed knowledge about the genomic regions harboring the major gluten protein genes in individual wheat cultivars for future efforts aimed at reducing the immunogenic potential of wheat flour.

SUBMITTER: Altenbach SB

PROVIDER: S-EPMC6249860 | biostudies-literature | 2018 Nov

REPOSITORIES: biostudies-literature

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Towards reducing the immunogenic potential of wheat flour: omega gliadins encoded by the D genome of hexaploid wheat may also harbor epitopes for the serious food allergy WDEIA.

Altenbach Susan B SB Chang Han-Chang HC Simon-Buss Annamaria A Jang You-Ran YR Denery-Papini Sandra S Pineau Florence F Gu Yong Q YQ Huo Naxin N Lim Sun-Hyung SH Kang Chon-Sik CS Lee Jong-Yeol JY

BMC plant biology 20181121 1

<h4>Background</h4>Omega-5 gliadins are a group of highly repetitive gluten proteins in wheat flour encoded on the 1B chromosome of hexaploid wheat. These proteins are the major sensitizing allergens in a severe form of food allergy called wheat-dependent exercise-induced anaphylaxis (WDEIA). The elimination of omega-5 gliadins from wheat flour through biotechnology or breeding approaches could reduce the immunogenic potential and adverse health effects of the flour.<h4>Results</h4>A mutant line ...[more]

PMID: 30463509

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Project description:BackgroundThe end-use quality of wheat flour varies as a result of the growth conditions of the plant. Among the wheat gluten proteins, the omega-5 gliadins have been identified as a major source of environmental variability, increasing in proportion in grain from plants that receive fertilizer or are subjected to high temperatures during grain development. The omega-5 gliadins also have been associated with the food allergy wheat-dependent exercise-induced anaphylaxis (WDEIA). Recently, transgenic lines with reduced levels of omega-5 gliadins were developed using RNA interference (RNAi). These lines make it possible to determine whether changes in the levels of omega-5 gliadins in response to environmental conditions and agronomic inputs may be responsible for changes in flour end-use quality.ResultsTwo transgenic wheat lines and a non-transgenic control were grown under a controlled temperature regimen with or without post-anthesis fertilizer and the protein composition of the resulting flour was analyzed by quantitative two-dimensional gel electrophoresis (2-DE). In one transgenic line, all 2-DE spots identified as omega-5 gliadins were substantially reduced without effects on other proteins. In the other transgenic line, the omega-5 gliadins were absent and there was a partial reduction in the levels of the omega-1,2 gliadins and the omega-1,2 chain-terminating gliadins as well as small changes in several other proteins. With the exception of the omega gliadins, the non-transgenic control and the transgenic plants showed similar responses to the fertilizer treatment. Protein contents of flour were determined by the fertilizer regimen and were similar in control and transgenic samples produced under each regimen while both mixing time and mixing tolerance were improved in flour from transgenic lines when plants received post-anthesis fertilizer.ConclusionsThe data indicate that omega-5 gliadins have a negative effect on flour quality and suggest that changes in quality with the growth environment may be due in part to alterations in the levels of the omega gliadins. Because a known food allergen and one of the major sources of environmentally-induced variation in wheat flour protein composition has been eliminated, the transgenic lines may yield flour with both improved end-use quality and more consistent functionality when grown in different locations.

Project description:Background and aimsThe ω-gliadin storage proteins of wheat are of interest in relation to their impact on grain processing properties and their role in food allergy, particularly the ω-5 sub-group and wheat-dependent exercise-induced anaphylaxis. The ω-gliadins are also known to be responsive to nitrogen application. This study therefore compares the effects of cultivar and nitrogen availability on the synthesis and deposition of ω-gliadins in wheat grown under field conditions in the UK, including temporal and spatial analyses at the protein and transcript levels.MethodsSDS-PAGE, western blotting and N-terminal amino acid sequencing were used to compare the patterns of ω-gliadin components in mature grain of six British wheat (Triticum aestivum) cultivars and their accumulation during the development of grain grown in field plots with varying nitrogen supply. Changes in gene expression during development were determined using real-time reverse transcription-PCR (RT-PCR). Spatial patterns of gene expression and protein accumulation were determined by in situ hybridization and immunofluorescence microscopy, respectively.Key resultsTwo patterns of ω-gliadins were identified in the six cultivars, including both monomeric 'gliadin' proteins and subunits present in polymeric 'glutenin' fractions. Increasing the level of nitrogen fertilizer in field plots resulted in increased expression of ω-gliadin transcripts and increased proportions of ω-5 gliadins. Nitrogen supply also affected the spatial patterns of ω-gliadin synthesis and deposition, which were differentially increased in the outer layers of the starchy endosperm with high levels of nitrogen.ConclusionsWheat ω-gliadins vary in amount and composition between cultivars, and in their response to nitrogen supply. Their spatial distribution is also affected by nitrogen supply, being most highly concentrated in the sub-aleurone cells of the starchy endosperm under higher nitrogen availability.

Project description:BACKGROUND: Alpha-gliadins form a multigene protein family encoded by multiple alpha-gliadin (Gli-2) genes at three genomic loci, Gli-A2, Gli-B2 and Gli-D2, respectively located on the homoeologous wheat chromosomes 6AS, 6BS, and 6DS. These proteins contain a number of important celiac disease (CD)-immunogenic domains. The alpha-gliadins expressed from the Gli-B2 locus harbour fewer conserved CD-epitopes than those from Gli-A2, whereas the Gli-D2 gliadins have the highest CD-immunogenic potential. In order to detect differences in the highly CD-immunogenic alpha-gliadin fraction we determined the relative expression level from the homoeologous Gli-2 loci in various tetraploid and hexaploid wheat genotypes by using a quantitative pyrosequencing method and by analyzing expressed sequence tag (EST) sequences. RESULTS: We detected large differences in relative expression levels of alpha-gliadin genes from the three homoeologous loci among wheat genotypes, both as relative numbers of expressed sequence tag (EST) sequences from specific varieties and when using a quantitative pyrosequencing assay specific for Gli-A2 genes. The relative Gli-A2 expression level in a tetraploid durum wheat cultivar ('Probstdorfer Pandur') was 41%. In genotypes derived from landraces, the Gli-A2 frequency varied between 12% and 58%. In some advanced hexaploid bread wheat cultivars the genes from locus Gli-B2 were hardly expressed (e.g., less than 5% in 'Lavett') but in others they made up more than 40% (e.g., in 'Baldus'). CONCLUSION: Here, we have shown that large differences exist in relative expression levels of alpha-gliadins from the homoeologous Gli-2 loci among wheat genotypes. Since the homoelogous genes differ in the amount of conserved CD-epitopes, screening for differential expression from the homoeologous Gli-2 loci can be employed for the pre-selection of wheat varieties in the search for varieties with very low CD-immunogenic potential. Pyrosequencing is a method that can be employed for such a 'gene family-specific quantitative transcriptome profiling'.

Project description:BackgroundWithin the complex wheat flour proteome, the gluten proteins have attracted most of the attention because of their importance in determining the functional properties of wheat flour doughs and their roles in human health conditions such as celiac disease and food allergies. However, certain non-gluten proteins also trigger immunological responses but may be present in flour in low amounts or obscured by the more abundant gluten proteins in two-dimensional gels of total protein preparations.MethodsNon-gluten proteins were preferentially extracted from the flour with a dilute salt solution and separated by two-dimensional gel electrophoresis. Proteins in 173 gel spots were identified by tandem mass spectrometry after cleavage with trypsin or chymotrypsin. Transgenic wheat lines in which specific groups of gluten proteins were suppressed by RNA interference were used to estimate the amount of carry-over of gluten proteins in the salt-soluble protein fraction.ResultsFifty-seven different types of non-gluten proteins were identified, including 14 types that are known or suspected immunogenic proteins. The predominant proteins in 18 gel spots were gluten proteins. Some of these also contained non-gluten proteins. Analysis of the salt-soluble proteins from a transgenic line in which omega-1,2 gliadins were eliminated by RNA interference indicated that certain omega-1,2 gliadins were present in large amounts in the salt-soluble fraction and obscured relatively small amounts of beta-amylase and protein disulfide isomerase. In comparison, analysis of a transgenic line in which alpha gliadins were absent revealed that glyceraldehyde-3 phosphate dehydrogenase was a moderately abundant protein that co-migrated with several alpha gliadins.ConclusionsIn this study, we constructed a proteomic map of the non-gluten protein fraction of wheat flour from the US wheat Butte 86 that complements a proteomic map of the total flour proteins developed previously for the same cultivar. Knowing the identities of low abundance proteins in the flour as well as proteins that are hidden by some of the major gluten proteins on two-dimensional gels is critical for studies aimed at assessing the immunogenic potential of wheat flour and determining which wheat proteins that should be targeted in future gene editing experiments to reduce the immunogenic potential of wheat flour.

Dataset Information

Towards reducing the immunogenic potential of wheat flour: omega gliadins encoded by the D genome of hexaploid wheat may also harbor epitopes for the serious food allergy WDEIA.

Publications

Towards reducing the immunogenic potential of wheat flour: omega gliadins encoded by the D genome of hexaploid wheat may also harbor epitopes for the serious food allergy WDEIA.

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