Functions and Composition Variations of Wheat Glutenin Proteins in Steamed Bread and Noodles

As a major food crop, wheat offers indispensable energy and nutrients to humans worldwide. With the living standards rising, the demand of high-quality wheat increases sharply. Wheat gluten proteins (glutenins and gliadins) are important components of seed storage proteins that affect the elasticity, strength or viscosity of dough. In this review, we summarize the composition of glutenin subunits in wheat grain and analyze the impact of glutenin on the traditional Chinese foods: steamed bread and noodles. Furthermore, we summarize the molecular markers used for wheat quality breeding. The advent of the recent wheat genomic will speed up the identification and quality breeding of novel glutenins.

Novel insights into the composition and characterization of the glutenin genes in common wheat Xinmai 26

High molecular weight glutenin subunits (HMW-GS) and Low molecular weight glutenin subunits (LMW-GS) in mature grains play important roles in the formation of glutenin macropolymer and gluten quality. To characterize the expressed glutenin genes of the bread wheat variety Xinmai 26 during seed development, in this study, we measured the dough rheological properties of mature grains through farinograph and gluten testing system, and revealed its strong gluten quality. The compositions of HMW-GS and LMW-GS were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Further, a total of 18 full-length transcripts were obtained by third-generation RNA sequencing, including 5 transcripts of HMW-GS genes and 13 transcripts of LMW-GS genes (8 intact genes and 5 pseudogenes). The deduced protein structures of transcript sequences exhibit the typical HMW-GS and LMW-GS structural characteristics. Moreover, a specific functional marker was developed to make better use of the extra cysteine residue of 1Dx5 subunit. This study provides an efficient method to accurately identify glutenin genes in bread wheat through matching full-length transcripts to their spectrum of glutenin, which will be helpful to understand the contributions of glutenin genes to wheat quality.

Allelic Variation at Glutenin Loci (Glu-1, Glu-2 and Glu-3) in a Worldwide Durum Wheat Collection and Its Effect on Quality Attributes

Durum wheat grains (Triticum turgidum L. ssp. durum) are the main source for the production of pasta, bread and a variety of products consumed worldwide. The quality of pasta is mainly defined by the rheological properties of gluten, an elastic network in wheat endosperms formed of gliadins and glutenins. In this study, the allelic variation at five glutenin loci was analysed in 196 durum wheat genotypes. Two loci (Glu-A1 and Glu-B1), encoding for high-molecular-weight glutenin subunits (HMW-GS), and three loci (Glu-B2, Glu-A3 and Glu-B3), encoding for low molecular weight glutenin subunits (LMW-GS), were assessed by SDS-PAGE. The SDS-sedimentation test was used and the grain protein content was evaluated. A total of 32 glutenin subunits and 41 glutenin haplotypes were identified. Four novel alleles were detected. Fifteen haplotypes represented 85.7% of glutenin loci variability. Some haplotypes carrying the 7 + 15 and 7 + 22 banding patterns at Glu-B1 showed a high gluten strength similar to those that carried the 7 + 8 or 6 + 8 alleles. A decreasing trend in grain protein content was observed over the last 85 years. Allelic frequencies at the three main loci (Glu-B1, Glu-A3 and Glu-B3) changed over the 1915–2020 period. Gluten strength increased from 1970 to 2020 coinciding with the allelic changes observed. These results offer valuable information for glutenin haplotype-based selection for use in breeding programs.

Pyramiding of Genes for Grain Protein Content, Grain Quality and Rust Resistance in Eleven Indian Bread Wheat Cultivars: A Multi-Institutional Effort

Improvement of grain protein content (GPC), loaf volume and resistance to rusts was achieved in 11 Indian wheat cultivars that are widely grown in four different agro-climatic zones of India. This involved use of marker-assisted backcrossing (MABC) for introgression and pyramiding of the following genes: (i) the high GPC gene Gpc-B1; (ii) HMW glutenin subunits 5 + 10 at Glu-D1 loci, and (iii) rust resistance genes, Yr36, Yr15, Lr24 and Sr24. GPC was improved by 0.8–3.3%, although high GPC was generally associated with yield penalty. Further selection among high GPC lines, allowed development of progenies with higher GPC associated with improvement in 1000-grain weight and grain yield in the following four cultivars: NI5439, UP2338, UP2382 and HUW468. The high GPC progenies (derived from NI5439) were also improved for grain quality using HMW glutenin subunits 5 + 10 at Glu-D1 loci. Similarly, progenies combining high GPC and rust resistance were developed in the backgrounds of following five cultivars: Lok1, HD2967, PBW550, PBW621 and DBW1. The improved pre-bred lines developed during the present study should prove useful for development of cultivars with improved nutritional quality associated with rust resistance in future wheat breeding programmes.

Diversity of high-molecular-weight glutenin subunits and evaluation of genetic similarities in spring bread wheats from different breeding centers

Background.Glutenin is a storage protein in wheat seeds, important for the quality of bread prepared from wheat. Studying glutenin polymorphism can help to identify valuable genotypes and promising new breeding lines for further crossings. The aim of this study was to identify subunits of glutenin and determine alleles at the Glu-1loci in the spring bread wheat germplasm collection.Materials and methods.A panel of 54 Russian and 76 Kazakh bread wheat germplasm accessions from various breeding centers was selected. Gliadin electrophoresis was carried out in a concentrating and separating polyacrylamide gel system following the Laemmli method. Glutenin subunits were identified according to the catalogue produced by Payne and Lawrence.Results and discussion.At the Glu-A1 locus, two alleles, band c, were identified, with different frequencies of occurrence among studied wheat accessions. The Glu-A1ballele occurred more frequently than Glu-A1сin the studied germplasm from all breeding centers. Meanwhile, six alleles, а, b, c, d, fand g, were found at theGlu-B1 locus. The most frequently occurring Glu-B1с allele encoded two subunits (7+9). The third homologous gene, Glu-D1, had only two identified alleles, aand d, with various frequencies among the studied wheat accessions. Wheat germplasm of various origin had specific combinations of glutenin subunits, providing different scores of grain quality. For example, the combination of glutenin subunits, 2*, 7+9 and 5+10, provided the highest score (= 9) of grain quality. A single change in the Glu-1subunit composition, 2*, 7+9 and 2+12, caused a reduction in grain quality (= 7 score); and the combination of Null, 7and 5+10 was accompanied by the lowest (= 6) grain quality. The analysis showed that two loci, Glu-A1 and Glu-B1, induced significant differences between wheat accessions originated from Tyumen and Chelyabinsk, while the accessions from Chelyabinsk and East Kazakhstan differed significantly at the Glu-A1and Glu-D1loci.

Post-Translational Cleavage of HMW-GS Dy10 allele improves the cookie-making quality in common wheat (Triticum aestivum)

Wheat is a major staple food crop worldwide because of the unique properties of wheat flour. High molecular weight glutenin subunits (HMW-GSs), which are among the most critical determinants of wheat flour quality, are responsible for the formation of glutenin polymeric structures via interchain disulfide bonds. We herein describe the identification of a new HMW-GS Dy10 allele (Dy10-m619SN). The amino acid substitution (serine-to-asparagine) encoded in this allele resulted in a partial post-translational cleavage that produced two new peptides. These new peptides disrupted the interactions among gluten proteins because of the associated changes to the number of available cysteine residues for interchain disulfide bonds. Consequently, Dy10-m619SN expression decreased the size of glutenin polymers and weakened glutens, which resulted in wheat dough with improved cookie-making quality, without changes to the glutenin-to-gliadin ratio. In this study, we clarified the post-translational processing of HMW-GSs and revealed a new genetic resource useful for wheat breeding.

Gluten Protein Compositional Changes in Response to Nitrogen Application Rate

Field trials were conducted to evaluate the effect of nitrogen level on wheat protein content and composition in 16 cultivars over two years at three locations. The nitrogen treatment comprised two nitrogen levels, 0 kg ha−1 as low and 100 kg ha−1 as high nitrogen, applied as top dressings of 50 kg nitrogen per ha at tillering and stem extension growth stages. Increased nitrogen level generally enhanced grain protein by 11.3% (11.5% vs. 12.8%). Considering protein composition determined by reversed phase–high-pressure liquid chromatography, higher nitrogen supply generally enhanced the proportion of total gliadins, α-gliadins, γ-gliadins and high-molecular-weight glutenin subunits by 1.1%, 2.0%, 3.7%, 0.6% and 0.9%, respectively, and reduced albumins and globulins, ω-gliadins, total glutenins and low-molecular-weight glutenin subunits by 1.1%, 1.7%, 1.9% and 3.2%. Under a high nitrogen level, the historical cultivars Libellula, San Pastore and U-1 had a higher protein content (13.1–15.2%) with significantly higher total gliadins, which resulted in a significantly higher gliadin/glutenin ratio (1.68–1.92). In the modern cultivars, protein content varied between 11.4% and 14.6% with a well-balanced gliadin/glutenin ratio (1.08–1.50), except for cultivar MV Nemere which had a high gliadin/glutenin ratio at both nitrogen levels (1.81 vs. 1.87). In summary, increasing nitrogen level enhanced grain protein content while the composition of gliadin and glutenin fractions was changed to a lesser extent and was largely cultivar specific and therefore should be considered for wheat baking quality assessment and breeding purposes.