Importance of amounts and proportions of high molecular weight subunits of glutenin for wheat quality

Identifying cis-Acting Elements Associated with the High Activity and Endosperm Specificity of the Promoters of Genes Encoding Low-Molecular-Weight Glutenin Subunits in Common Wheat (Triticum aestivum)

Low-molecular-weight glutenin subunits (LMW-GSs) associated with bread-baking quality and flour nutrient quality accumulate in endosperms of common wheat and related species. However, the mechanism underlying the expression regulation of genes encoding LMW-GSs has not been fully elucidated. In this study, we identified LMW-D2 and LMW-D7, which are highly and weakly expressed, respectively, via the analysis of RNA-sequencing data of Chinese Spring wheat and wheat transgenic lines transformed with 5' deletion promoter fragments and GUS fusion constructs. The 605-bp fragment upstream of the LMW-D2 start codon could drive high levels of GUS expression in the endosperm. The truncated endosperm box located at the -300 site resulted in the loss of LMW-D2 promoter activity, and a single-nucleotide polymorphism on the GCN4 motif was closely related to the expression of LMW-GSs. TCT and TGACG motifs, as well as the others located on the 5' distal end, might also be involved in the transcription regulation of LMW-GSs. In transgenic lines, fusion proteins of LMW-GS and GUS were deposited into protein bodies. Our findings provide new insights into the mechanism underlying the transcription regulation of LMW-GSs and will contribute to the development of wheat endosperm as a bioreactor for the production of nutraceuticals, antibodies, vaccines, and medicinal proteins.

Bread-Making Potential and Yielding of Hybrid Wheat Under Varied Agronomic and Environmental Factors

The purpose of this study was to determine the effect of simplified tillage systems (RT, NT) in comparison with conventional tillage (CT) on technological grain quality and baking value, as well as of hybrid wheat grown under variable weather conditions. A three-year field trial experiment was conducted using a randomised block design, in triplicate. The factors studied were as follows: I - three tillage systems - no-tillage (NT), reduced (RT), and conventional (CT); II - two winter wheat cultivars ‘Hylux’ (cv. hybrid) and for comparison ‘Bogatka’ (cv. common). The use of CT and RT tillage systems compared to NT significantly increased yield by 8.9 and 7.7%, respectively, and selected grain quality parameters along with a more favorable gluten protein profile. The flour obtained, with water absorption above 58.0%, can be classified as strong flour with good farinographic and alveograph parameters. The genetic characteristics of the wheat cultivars determined the technological quality of the grain and the baking value, as well as the grain yield. For ‘Hylux’ cv. hybrid wheat, there was a higher yield and better grain quality, which contained significantly more gliadins and glutenins, and the flour was characterised by higher parameters that determine the preferred viscoelastic properties of the dough. The common ‘Bogatka’ wheat cv. accumulated higher contents of ω gliadins and LMW and HMW glutenin subunits in the grain, while for α/β and γ gliadin contents the difference was not significant. A fairly dry period (June–July) of wheat ripening reduced the grain yield but was favourable for higher values of quality characteristics, gluten protein fractions, as well as the farinographic (WAF, DDT, DS) and alveograph (W, P, L) parameters.

Effects of Nitrogen Fertilizer on Quality Characteristics of Wheat with the Absence of Different Individual High-Molecular-Weight Glutenin Subunits (HMW-GSs)

High-molecular-weight glutenin subunits (HMW-GSs) are important components of gluten, which determine the grain quality of wheat. In this study, we investigated the effects of nitrogen (N) fertilizer application on the synthesis and accumulation of grain protein and gluten quality in wheat lines with different HMW-GSs absent. The results showed that the absence of the HMW-GS in the wheat variety Ningmai 9 significantly decreased the contents of gluten, glutenin macropolymer (GMP), protein compositions, HMW-GS and HMW-GS/LMW-GS. The reduction in glutenins was compensated to some extent by an increase of gliadins. The absence of x-type HMW-GSs (1, 7 and 2 subunits) had a greater effect on gluten and GMP properties than y-type HMW-GSs (8 and 12 subunits). The content of protein compositions, gluten and GMP increased with an increase of N level; however, the increment in wheat lines with the absence of HMW-GS, especially in Ax1a, Bx7a and Dx2a, was lower than that in the wild type under various N levels. The expression level of genes encoding HMW-GSs, and activities of nitrate reductase (NR) and glutamine synthetase (GS), differed significantly among the investigated wheat lines. The reduction in gene expression and activities in Ax1a and Dx2a may account for the reductions in gluten, GMP, protein compositions, HMW-GS and HMW-GS/LMW-GS.

Evaluation of flour protein for different bread wheat genotypes

Six different bread wheat genotypes; two Egyptian commercial varieties (control); Giza-168 and Gemmeiza-11, and four promising lines; L84 and L148, resulted via hybridization and M10 and M34 via radiation mutation program) were rheologically evaluated using extensograph and for protein, analysis using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The radiation mutant M10 and M34 had the highest maximum resistance which is a very good indicator of strong gluten. The amount of gluten content was higher in M10, L148, and M34 compared to the control samples Gz168 and Gm11. Sulfide amino acids (CYS and MET) are slightly higher in M10. The electrophoretic results and amino acid analyzers show that the best technological quality was exhibited by M10. Radiation mutants wheat genotypes have a protein with good characteristics, mainly gluten which is significantly higher compared to control samples. The rheological properties measured as extensograph and gel electrophoresis were much better in irradiated lines M10 and M34.

Proteins and Metabolites as Indicators of Flours Quality and Nutritional Properties of Two Durum Wheat Varieties Grown in Different Italian Locations

Durum wheat is an important food source in Mediterranean countries, and Italy is the major producer of durum wheat in Europe. The quality of durum wheat flours depends on the type and amount of gluten proteins and starch while flour nutritional value rests on metabolite contents such as polyphenols. In this work, two Italian cultivars, Iride and Svevo, were analyzed for two years (2016-2017) in four Italian regions to explore how the environment affects: (i) reserve proteome; (ii) starch content and composition; and (iii) free, conjugated, bound phenolics and antioxidant capacity. The impact of environmental and meteorological conditions was significant for many traits. Regardless of the cultivation site, in 2017, a year with less rainfall and a higher temperature during grain filling, there was an increase in low molecular weight glutenins, in the glutenin/gliadin ratio and in the A-type starch granules size, all parameters of higher technological quality. In the same year, the cultivars showed higher amounts of polyphenols and antioxidant capacity. In conclusion, the two wheat cultivars, selected for their medium to high yield and their good quality, had higher performances in 2017 regardless of their sowing locations.

Bread making potential of Triticum aestivum and Triticum spelta species

The aim of this study was to assess the effect of two winter wheat species: Triticum aestivum ssp. vulgare, and Triticum spelta, cultivated in different percentage of cereals in crop rotation, on their bread making potential. The analyzed grain samples were obtained from a field experiment conducted during three years 2014-2016 at the Experimental Station in Osiny (51°35’, 21°55’), Institute of Soil Science and Plant Cultivation, State Research Institute, Puławy, Poland. The experiment was established following different percentages of shared cereals in crop rotation (SCCR): 50, 75 and 100%. Wheat cultivation was performed in accordance with good agricultural practice standards. Protein content, gluten content, Zeleny sedimentation index and alveograph properties were determined. Wheat species strongly influenced bread potential. The Triticum aestivum compared to Triticum spelta was characterized by significantly higher gluten quality and Zeleny sedimentation index as well as better alveograph properties. Common wheat showed the highest baking value (W). Spelt wheat was characterized by the lowest tenacity (P) and the highest extensibility (L). Moreover, the percentage of cereals in crop rotation had an effect on grain and dough quality parameters. Cultivation of wheat in 100% share of cereals resulted in the lowest grain and dough quality.

Effects of microwave treatment of durum wheat kernels on quality characteristics of flour and pasta

The influence of microwave treatment of hydrated durum wheat kernels of two different cultivars (cv Aureo and Sfinge), on wholemeal flour and pasta quality was addressed. Size exclusion-HPLC and electrophoresis analysis were used to investigate changes in the gluten network arrangement as affected by the microwave treatment. Rheological properties of dough, cooking quality and sensory properties of pasta were also assessed. Results suggested that the microwave treatment on hydrated durum wheat kernels blocks gluten protein conformation through SS bonds formation and the free -SH are no longer able to create a strong network during pasta processing, due to the conformational changes. Rheological study of dough confirmed that the modifications induced by microwave treatment greatly affected pasta making characteristics of wheat flour, with significant negative consequences on product quality, especially for pasta cooking quality. Pasta from treated durum wheat showed low sensory quality, mainly due to high bulkiness and adhesiveness.

Perspective on Wheat Yield and Quality with Reduced Nitrogen Supply

Wheat is an important cereal crop with a high demand for nitrogen (N) fertilizer to enable the grain protein accumulation that is necessary for baking and processing quality. Here, perspectives for the development of improved wheat genotypes with higher yield stability, better grain quality, and improved N use efficiency to lower environmental impacts are discussed. The development of improved wheat genotypes, for example, genotypes that lack storage proteins that do not contribute to baking quality (e.g., by genome editing), in combination with appropriate N fertilizer management to prevent N losses into the environment underpins a novel approach to improving N use efficiency. This approach may be particularly applicable to wheats grown for animal feed, which have lower quality and functionality requirements.

Benefits and Limitations of Lab-on-a-Chip Method over Reversed-Phase High-Performance Liquid Chromatography Method in Gluten Proteins Evaluation

RP-HPLC (reversed-phase high-performance liquid chromatography) is widely used to determine the amounts of the different gluten protein types. However, this method is time-consuming, especially at early stages of wheat breeding, when large number of samples needs to be analyzed. On the other hand, LoaC (Lab-on-a-Chip) technique has the potential for a fast, reliable, and automatable analysis of proteins. In the present study, benefits and limitations of Lab-on-a-Chip method over RP-HPLC method in gluten proteins evaluation were explored in order to determine in which way LoaC method should be improved in order to make its results more compliant with the results of RP-HPLC method. Strong correlation (P≤0.001) was found between numbers of HMW glutenin peaks determined by LoaC and RP-HPLC methods. Significant correlations (P≤0.05) were obtained between percentages of HMW and LMW glutenin subunits calculated with regard to total HMW + LMW area. Even more significant correlation (P≤0.001) was found when percentages of individual HMW areas were calculated with regard to total HMW. RP-HPLC method showed superiority in determination of gliadins since larger number and better resolution of gliadin peaks were obtained by this method.

Effect of high molecular weight glutenin subunit composition in common wheat on dough properties and steamed bread quality

BACKGROUND

Steamed bread is a popular staple food in Asia with different flour quality requirements from pan bread. Little is known about how glutenin characteristics affect steamed bread quality. This work investigated how deletions of high-molecular-weight glutenin subunits (HMW-GS) influence gluten properties and Chinese steamed bread quality using 16 wheat lines grown in Texas.

RESULTS

Although similar in protein content (134-140 mg g⁻¹), gluten composition and dough properties differed widely among the lines. Compared with non-deletion lines, deletion lines had lower (P < 0.05) unextractable polymeric protein (294 vs 470 mg g⁻¹), HMW-GS/low-molecular-weight glutenin subunit ratio (0.25 vs 0.41), dough force to extend (0.16 vs 0.44 N) and mixing peak time (2.03 vs 4.52 min). Deletion lines with HMW-GS composition of 2*/17+_/5+_ and 2*/17+_/2+12 showed moderate gluten strength (mixing peak time, 1.96-2.94 min; force to extend, 0.18-0.23 N) and high dough extensibility (106-129 mm). These lines also produced good steamed bread quality (score, 60.8-65.0) with good elasticity and crumb structure.

CONCLUSION

Deletion at Glu-B1y and/or Glu-D1y loci in high-strength hard wheat produced good dough properties for steamed bread. This suggests that wheat functionality for steamed bread can be improved by manipulating HMW-GS composition.

Wheat storage proteins in transgenic rice endosperm

Transgenic rice seed expressing wheat HMW glutenin subunit was characterized to study the effects of the wheat prolamin on the protein expression pattern and protein size distribution in the endosperm and the functional and rheological properties of the rice flour and dough. Significant differences were found in the protein expression pattern between the transgenic and wild type samples. Comparing the protein expression profiles of transgenic and nontransgenic plants, combined with proteomic-based studies, indicated increased protein disulfide isomerase (PDI) levels in the transgenic rice lines. The accurate molecular size of HMW-GS in rice endosperm was identified by MALDI-TOF-MS analysis. The expressed wheat HMW (subunit 1Dx5) GS showed a positive effect on the functional properties of rice dough by significantly increasing the size distribution of the polymeric protein fraction and modifying the dough mixing parameters.

Bread Wheat Quality: Some Physical, Chemical and Rheological Characteristics of Syrian and English Bread Wheat Samples

The relationships between breadmaking quality, kernel properties (physical and chemical), and dough rheology were investigated using flours from six genotypes of Syrian wheat lines, comprising both commercially grown cultivars and advanced breeding lines. Genotypes were grown in 2008/2009 season in irrigated plots in the Eastern part of Syria. Grain samples were evaluated for vitreousness, test weight, 1000-kernel weight and then milled and tested for protein content, ash, and water content. Dough rheology of the samples was studied by the determination of the mixing time, stability, weakness, resistance and the extensibility of the dough. Loaf baking quality was evaluated by the measurement of the specific weight, resilience and firmness in addition to the sensory analysis. A comparative study between the six Syrian wheat genotypes and two English flour samples was conducted. Significant differences were observed among Syrian genotypes in vitreousness (69.3%–95.0%), 1000-kernel weight (35.2–46.9 g) and the test weight (82.2–88.0 kg/hL). All samples exhibited high falling numbers (346 to 417 s for the Syrian samples and 285 and 305 s for the English flours). A significant positive correlation was exhibited between the protein content of the flour and its absorption of water (r = 0.84 **), as well as with the vitreousness of the kernel (r = 0.54 *). Protein content was also correlated with dough stability (r = 0.86 **), extensibility (r = 0.8 **), and negatively correlated with dough weakness (r = −0.69 **). Bread firmness and dough weakness were positively correlated (r = 0.66 **). Sensory analysis indicated Doumah-2 was the best appreciated whilst Doumah 40765 and 46055 were the least appreciated which may suggest their suitability for biscuit preparation rather than bread making.

Comparative study of the effect of incorporated individual wheat storage proteins on mixing properties of rice and wheat doughs

The aim of this work was to compare the effects of incorporated wheat storage proteins on the functional properties of rice and wheat flours. The advantage of rice as a base flour compared to wheat is that it does not contain any wheat flour components and, therefore, has no interactive effect between wheat glutenin proteins. The incorporation of individual HMW glutenin subunit proteins (Bx6, Bx7, and By8) in different ratios had significant positive effects on the mixing requirements of both rice and wheat doughs. Reconstitution experiments using two x+y type HMW-GS pairs together with a bacterially expressed LMW-GS have been also carried out in this study. The largest effects of polymer formation and mixing properties of rice flour dough were observed when Bx and By subunits were used in a 1:1 ratio and HMW and LMW glutenin subunits in a 1:3 ratio. However, using the same subunit ratios in wheat as the base flour, these synergistic effects were not observed.

Preparation and characterization of enzymatically hydrolyzed prolamins from wheat, rye, and barley as references for the immunochemical quantitation of partially hydrolyzed gluten

Celiac disease (CD) is a permanent gastrointestinal disorder characterized by the intolerance to a group of proteins called gluten present in wheat, rye, barley, and possibly oats. The only therapy is a strict lifelong gluten-free diet. The standard method for gluten determination in foods produced for CD patients is the R5-enzyme-linked immunosorbent assay (ELISA) as proposed by the recent Codex Alimentarius Draft Revised Standard. This test is based on the determination of prolamins, the alcohol-soluble proteins of gluten, and is available as a sandwich ELISA for intact proteins and as a competitive ELISA for gluten-derived peptides. While the suitability of the sandwich ELISA including a wheat prolamin (gliadin) reference for calibration has been shown by various studies and a ring test, the competitive ELISA still lacks a convenient reference for the quantitation of gluten peptides in fermented cereal foods (e.g., sourdough products, starch syrup, malt extracts, beer). Therefore, the aim of the present study was to prepare a suitable reference for the quantitation of partially hydrolyzed gluten in fermented wheat, rye, and barley products. The prolamin fractions from barley (hordein) and rye (secalin) were isolated from corresponding flours by means of a modified preparative Osborne fractionation. The prolamin fraction from wheat was obtained as reference gliadin from the Prolamin Working Group. The prolamin fractions were successively digested by pepsin and trypsin or pepsin and chymotrypsin procedures, which have been used for CD-specific toxicity tests on cereal storage proteins for many years. The protein/peptide content (N x 5.7) of the prolamin fractions and digests, which was the basis for the calculation of the gluten content by means of ELISA, varied between 67.1% and 96.0%. The prolamin fractions and enzymatic digests were then tested for their response in both sandwich and competitive assays. Intact prolamins responded similarly in both ELISA showing no important differences between the cereals. In the case of digested proteins, however, the sandwich ELISA was considerably less sensitive than the competitive ELISA. The former provided approximately 40% and the latter 70% of the signal intensity obtained with the intact prolamins. Thus, the combination of the competitive ELISA and the enzymatic digests of prolamin fractions as reference was considered to be an adequate system for the analysis of partially hydrolyzed gluten. The limit of detection using a peptic-tryptic hordein digest as reference was 2.3 microg prolamin equivalent per milliliter, and the limit of quantitation was 6.7 microg prolamin equivalent per milliliter. This system was applied for the determination of gluten equivalents in five commercial beverages based on fermented cereals.

Homoeologous recombination within bread wheat to develop novel combinations of HMW-GS genes: transfer of the Glu-A1 locus to chromosome 1D

In an attempt to improve the bread-making quality within hexaploid wheat by elaborating novel high-molecular weight glutenin subunits (HMW-GS) combinations useful in wheat-breeding programmes, a 1A chromosome fragment carrying the Glu-A1 locus encoding the subunit Ax2*, was translocated to the long arm of chromosome 1D. The partially isohomoeoallelic line, designated RR239, had a meiotic behaviour as regular as cv. Courtot. It was characterised using genomic in situ hybridization and microsatellite markers as well as biochemical and proteomic approaches. The translocated 1D chromosome had an interstitial 1AL segment representing in average 30% of the recombinant arm length that was confirmed by molecular analysis. The genetic length of the removed segment in chromosome 1DL was estimated to be at least 51 cM, and that of the interstitial 1AL translocation to be at least 33 cM. Proteome analysis performed on total endosperm proteins revealed variation in amounts, 8 spots and 1 spot being up- and downregulated, respectively. Quantitative variations in HMW-GS were observed for the Glu-A1 (Ax2*) and Glu-B1 (Bx7 + By8) loci in response to duplication of the Glu-A1 locus.

Development of isohomoeoallelic lines within the wheat cv. Courtot for high molecular weight glutenin subunits: transfer of the Glu-D1 locus to chromosome 1A

Wheat quality depends on protein composition and grain protein content. High molecular weight glutenin subunits (HMW-GS) play an important role in determining the viscoelastic properties of gluten. In an attempt to improve the bread-making quality of hexaploid wheat by elaborating novel HMW-GS combinations, a fragment of wheat chromosome 1D containing the Glu-D1 locus encoding the Dx2+Dy12 subunits was translocated to the long arm of chromosome 1A using the ph1b mutation. The partially isohomoeoallelic line selected was characterized using cytogenetical and molecular approaches to assess the amount of chromatin introgressed in the translocated 1A chromosome. Triple-target genomic in situ hybridization indicated that the translocated 1A chromosome had a terminal 1D segment representing 25% of the length of the recombinant long arm. The translocation was also identified on the long arm using molecular markers, and its length was estimated with a minimum of 91 cM. Proteome analysis was performed on total endosperm proteins. Out of the 152 major spots detected, 9 spots were up-regulated and 4 spots were down-regulated. Most of these proteins were identified as alpha-, beta-, gamma-gliadins assigned to the chromosomes of homoeologous groups 1 and 6. Quantitative variations in the HMW-GS were only observed in subunit Dy12 in response to duplication of the Glu-D1 locus.

Quantitative protein composition and baking quality of winter wheat as affected by late sulfur fertilization

Increasing prices for wheat products and fertilizers, as well as reduced sulfur (S) contributions from the atmosphere, call for an improvement of product quality and agricultural management. To detect the impact of a time-dependent S fertilization, the quantitative protein composition and the baking quality of two different wheat cultivars, Batis and Turkis, were evaluated. The glutathione concentration in grains serves as a reliable marker of the need for added S fertilizer. The quantitation of gliadins and glutenin subunits by reversed-phase high-performance liquid chromatography confirmed that S-rich proteins significantly increased with S fertilization, whereas the S-poor proteins significantly decreased. Proteome analysis by means of high-resolution protein profiles detected 55 and 37 proteins from Batis and Turkis changed by late S fertilization. A microscale baking test using wholemeal flour was implemented for the evaluation of baking quality, and late S fertilization was found to improve the composition of gluten proteins and baking quality.

Detection of high molecular weight glutenin subunits in triticale (x Triticosecale Wittm.) Cultivars by capillary zone electrophoresis

An improved method for separating and characterizing high molecular weight glutenin subunits (HMW-GS) in hexaploid triticale by capillary zone electrophoresis (CZE) was developed. A low-concentrate mixture of hydrophilic polymers, poly(vinylpyrrolidone) (PVP) and hydroxypropylmethylcellulose (HPMC), in an isoelectric buffer was employed for dynamic coating of the capillary inner wall. In separation buffer PVP with lower concentrated poly(ethylene oxide) (PEO) was replaced. The CZE electropherograms of HMW-GS showed two group peaks in accordance with x- and y-type subunits with migration times of 6.8-7.8 and 8.4-11.5 min, respectively. In total, 14 HMW subunits (2 subunits encoded by Glu-A1 locus and 12 by Glu-B1) were identified. The CZE analyses revealed that each of the subunits Bx7 and By8 determined by SDS-PAGE makes up three subunits (Bx6.8, Bx7, and Bx7* and By8, By8*, and new By8**, respectively), with different migration times. It was also shown that the subunits By18 and By20 in triticale determined by SDS-PAGE have different migration times in comparison with the same subunits in bread wheat. For these new HMW-GS, the following names were assigned: By18* instead of By18 and By20* instead of By20. The presented CZE method is an efficient alternative to the SDS-PAGE procedure for early selection of useful triticale genotypes with good breadmaking quality.

Chemistry of gluten proteins

Gluten proteins play a key role in determining the unique baking quality of wheat by conferring water absorption capacity, cohesivity, viscosity and elasticity on dough. Gluten proteins can be divided into two main fractions according to their solubility in aqueous alcohols: the soluble gliadins and the insoluble glutenins. Both fractions consist of numerous, partially closely related protein components characterized by high glutamine and proline contents. Gliadins are mainly monomeric proteins with molecular weights (MWs) around 28,000-55,000 and can be classified according to their different primary structures into the alpha/beta-, gamma- and omega-type. Disulphide bonds are either absent or present as intrachain crosslinks. The glutenin fraction comprises aggregated proteins linked by interchain disulphide bonds; they have a varying size ranging from about 500,000 to more than 10 million. After reduction of disulphide bonds, the resulting glutenin subunits show a solubility in aqueous alcohols similar to gliadins. Based on primary structure, glutenin subunits have been divided into the high-molecular-weight (HMW) subunits (MW=67,000-88,000) and low-molecular-weight (LMW) subunits (MW=32,000-35,000). Each gluten protein type consists or two or three different structural domains; one of them contains unique repetitive sequences rich in glutamine and proline. Native glutenins are composed of a backbone formed by HMW subunit polymers and of LMW subunit polymers branched off from HMW subunits. Non-covalent bonds such as hydrogen bonds, ionic bonds and hydrophobic bonds are important for the aggregation of gliadins and glutenins and implicate structure and physical properties of dough.

The toxicity of high molecular weight glutenin subunits of wheat to patients with coeliac disease

OBJECTIVES

The ability of the gliadin fraction of wheat gluten to exacerbate coeliac disease is well documented. We investigated the possible toxicity of high molecular weight glutenin subunits (HMW-GS) in coeliac disease in vitro using gluten-sensitive T cells, and in vivo with challenge studies in patient volunteers.

METHODS

A mixture of four HMW-GS was chemically separated from wheat flour and checked for purity by HPLC, SDS-PAGE and ELISA. T-cell lines, grown up from small intestinal biopsies from coeliac patients (n=17), were tested for their reactivity to HMW-GS. Adults with coeliac disease and who were on a gluten-free diet (n=3) underwent in-vivo challenges with HMW-GS. Duodenal biopsies, taken prior to the challenge and at intervals up to 6 h afterwards, were assessed for morphology, intra-epithelial lymphocyte count, and interleukin 15 (IL-15) expression, by immunohistochemistry.

RESULTS

T-cell lines from 11 of 17 patients were stimulated by HMW-GS. There was a significant change in small intestinal morphology 4 h after commencing infusions with HMW-GS in all three subjects. For example villus height to crypt depth ratios were reduced in the three patients from 3.0+/-0.5 to 1.29+/-0.2, 2.53+/-0.7 to 0.81+/-0.6 and 3.0+/-0.7 to 1.85+/-0.3, P<0.0001 in all cases. There was increased expression of IL-15 in the small intestine from 2 h after the HMW-GS challenges.

CONCLUSION

Mixed HMW-GS stimulate T-cell lines from some coeliac patients and exacerbate coeliac disease in vivo, inducing expression, within 2 h, of IL-15. This suggests an innate immune response to these proteins.

Specific IgE determination to epitope peptides of omega-5 gliadin and high molecular weight glutenin subunit is a useful tool for diagnosis of wheat-dependent exercise-induced anaphylaxis

Wheat omega-5 gliadin and a high m.w. glutenin subunit (HMW-glutenin) have been reported as major allergens in wheat-dependent exercise-induced anaphylaxis. A simultaneous detection of specific IgE to epitope sequences of both proteins is considered to be a reliable method for diagnosis of wheat-dependent exercise-induced anaphylaxis. However, the IgE-binding epitope of HMW-glutenin remains unknown. The aim of this study was to determine the IgE-binding epitopes of HMW-glutenin to establish a useful system of identifying patients with wheat-dependent exercise-induced anaphylaxis. For determination of IgE-binding epitopes of HMW-glutenin overlapping peptides were synthesized and reactivities of IgE Abs in the sera of patients to those peptides were analyzed. Three IgE-binding epitopes, QQPGQ, QQPGQGQQ, and QQSGQGQ, were identified within primary sequence of HMW-glutenin. Epitope peptides, which include IgE-binding sequences of omega-5 gliadin and a HMW-glutenin, were synthesized and peptide-specific IgE Abs were measured by CAP-System fluorescent enzyme immunoassay. Twenty-nine of 30 patients with wheat-dependent exercise-induced anaphylaxis had specific IgE Abs to these epitope peptides. None of the 25 sera from healthy subjects reacted to both epitope peptides. Twenty-five patients with atopic dermatitis who had specific IgE to wheat and/or gluten had very low or nonexistent levels of epitope peptide-specific IgE Abs. These results indicated that measurement of IgE levels specific to epitope peptides of omega-5 gliadin and HMW-glutenin is useful as an in vitro diagnostic method for the assessment of patients with wheat-dependent exercise-induced anaphylaxis.

Stable expression of 1Dx5 and 1Dy10 high-molecular-weight glutenin subunit genes in transgenic rye drastically increases the polymeric glutelin fraction in rye flour

We generated and characterized transgenic rye synthesizing substantial amounts of high-molecular-weight glutenin subunits (HMW-GS) from wheat. The unique bread-making characteristic of wheat flour is closely related to the elasticity and extensibility of the gluten proteins stored in the starchy endosperm, particularly the HMW-GS. Rye flour has poor bread-making quality, despite the extensive sequence and structure similarities of wheat and rye HMW-GS. The HMW-GS 1Dx5 and 1Dy10 genes from wheat, known to be associated with good bread-making quality were introduced into a homozygous rye inbred line by the biolistic gene transfer. The transgenic plants, regenerated from immature embryo derived callus cultures were normal, fertile, and transmitted the transgenes stably to the sexual progeny, as shown by Southern blot and SDS-PAGE analysis. Flour proteins were extracted by means of a modified Osborne fractionation from wildtype (L22) as well as transgenic rye expressing 1Dy10 (L26) or 1Dx5 and 1Dy10 (L8) and were quantified by RP-HPLC and GP-HPLC. The amount of transgenic HMW-GS in homozygous rye seeds represented 5.1% (L26) or 16.3% (L8) of the total extracted protein and 17% (L26) or 29% (L8) of the extracted glutelin fraction. The amount of polymerized glutelins was significantly increased in transgenic rye (L26) and more than tripled in transgenic rye (L8) compared to wildtype (L22). Gel permeation HPLC of the un-polymerized fractions revealed that the transgenic rye flours contained a significantly lower proportion of alcohol-soluble oligomeric proteins compared with the non-transgenic flour. The quantitative data indicate that the expression of wheat HMW-GS in rye leads to a high degree of polymerization of transgenic and native storage proteins, probably by formation of intermolecular disulfide bonds. Even gamma-40k secalins, which occur in non-transgenic rye as monomers, are incorporated into these polymeric structures. The combination 1Dx5 + 1Dy10 showed stronger effects than 1Dy10 alone. Our results are the first example of genetic engineering to significantly alter the polymerization and composition of storage proteins in rye. This may be an important step towards improving bread-making properties of rye whilst conserving its superior stress resistance.