Glutenin Subunits Research Articles

HMW-GS at Glu-B1 Locus Affects Gluten Quality Possibly Regulated by the Expression of Nitrogen Metabolism Enzymes and Glutenin-Related Genes in Wheat.

In this study, we investigated the effect of high-molecular-weight glutenin subunits (HMW-GSs) on gluten quality and glutenin synthesis based on the cytological, physicochemical, and transcriptional levels using Xinong1718 and its three near-isogenic lines (NILs). Cytological observations showed that the endosperm of Glu-1Bh with Bx14+By15 accumulated more abundant and larger protein bodies at 10 and 16 days after anthesis than the other NILs. Glu-1Bh exhibited higher nitrogen metabolism enzyme gene expression and activity levels. The transcriptional levels of genes encoding HMW-GSs, protein folding, and transcription factors differed significantly among the NILs, and they were highest in Glu-1Bh. Our results demonstrate that variations in the expression patterns of nitrogen metabolism and glutenin synthesis-related genes may account for the differences in the accumulation of glutenin, glutenin macropolymers, and protein bodies, thereby affecting the structural and thermal stability of gluten. These findings provide novel insights into how different HMW-GSs might improve the quality of wheat.

Effect of extrusion on the polymerization of wheat glutenin and changes in the gluten network

The changes in the gluten network during extrusion treatment were studied by assessing the polymerization behavior of glutenin. Gluten samples were extruded at different barrel temperatures, screw speeds, and flow rates. The results indicated that high molecular weight glutenin subunits increased while free sulfhydryl groups and low molecular weight glutenin subunits decreased as the screw speeds and flow rates increased during extrusion treatment. Specific β-sheet structures of gluten clearly increased, while α-helices and β-turns fluctuated during extrusion processing, thus forming a tight gluten network. The characteristics of the protein network were evaluated by confocal laser scanning microscopy. The results showed that a homogeneous and denser gluten network was formed at higher extrusion temperatures during the extrusion process, which may be related to the polymerization of low-molecular-weight glutenin subunits. This study provides a theoretical basis for the improvement and regulation of extrusion quality during the gluten extrusion process.

Relationships of protein composition, gluten structure, and dough rheological properties with short biscuits quality of soft wheat varieties

AbstractUnderstanding the contribution of protein composition and gluten structure to dough property and biscuit baking is crucial to improve soft wheat (Triticum aestivum L.) grain quality. Thus, the relationships of protein composition, gluten structure, and dough rheological properties with short biscuits quality was investigated using 10 Chinese soft wheat varieties. Content of grain protein, flour protein, gliadin, glutenin, and high and low molecular weight glutenin subunits were significantly positively correlated with hardness of biscuit, but negatively correlated with spread factor and sensory score. Gluten of wheat varieties with lower dough strength and better biscuit quality showed thinner walls of apertures and more regular apertures in its microstructure. The gluten with higher strength had more apertures and antiparallel β‐sheets and fewer α‐helices. Moreover, dough with a higher softening degree was easier to stretch and tended to produce biscuits with larger diameter and crispier taste during baking. In conclusion, main wheat quality characteristics that can be used to select grain samples suitable for making tasty biscuits were recommended as follows: flour protein content, wet gluten content and microstructure, Zeleny sedimentation value, and dough softening degree.

Effects of Nitrogen Application in the Wheat Booting Stage on Glutenin Polymerization and Structural-Thermal Properties of Gluten with Variations in HMW-GS at the Glu-D1 Locus.

Wheat gluten properties can be improved by the application of nitrogen. This study investigates the effects of nitrogen application in the booting stage on glutenin polymerization during grain-filling and structural–thermal properties of gluten based on the high-molecular-weight glutenin subunits (HMW-GSs) using near-isogenic lines (Glu-1Da and Glu-1Dd). The nitrogen rate experiment included rates of 0, 60, 90, and 120 kg N ha−1 applied with three replicates. Nitrogen significantly improved the grain quality traits (wet gluten contents, Zeleny sedimentation values, and maximum resistance) and dough strength (dough development time, dough stability time, and protein weakening), especially in wheat with the Glu-1Da allele. Nitrogen increased the protein composition contents, proportions of glutenins and HMW-GSs, and disulfide bond concentration in the flours of Glu-1Da and Glu-1Dd, and accelerated the polymerization of glutenins (appearing as glutenin macropolymer) during grain-filling, where nitrogen enhanced the accumulation and polymerization of glutenins more for line containing Glu-1Da than Glu-1Dd. The β-sheets, α-helix/β-sheet ratio, microstructures, and thermal stability were also improved to a greater degree by nitrogen for gluten with Glu-1Da compared to Glu-1Dd. Nitrogen treatment was highly effective at improving the gluten structural‒thermal properties of wheat in the booting stage, especially with inferior glutenin subunits.

Proteomic Analysis of Proteins Responsive to Drought and Low Temperature Stress in a Hard Red Spring Wheat Cultivar.

Drought stress is becoming more prevalent with global warming, and has been shown to have large effects on gluten proteins linked to wheat bread making quality. Likewise, low temperature stress can detrimentally affect proteins in wheat. This study was done to determine the differential abundance of high molecular weight (HMW) glutenin proteins in a drought and low temperature stressed high quality hard red spring wheat cultivar (PAN3478), against a control. The treatments were applied in the greenhouse at the soft dough stage. HMW glutenin proteins were extracted from the flour, and were separated by using two-dimensional gel electrophoresis. Protein spots that had p values lower than 0.05 and fold values equal to or greater than 1.2 were considered to be significantly differentially abundant. These proteins were further analyzed by using tandem mass spectrometry. There was a 1.3 to 1.8 fold change in 17 protein spots due to the cold treatment. The drought treatment caused a 1.3 to 3.8 fold change in 19 protein spots. These spots matched either HMW or low molecular weight (LMW) glutenin subunits. In the latter case, the C subunits of LMW glutenins were notably found to be up-regulated under both stress conditions. All the proteins that have been identified can directly influence dough characteristics. Data are available via ProteomeXchange with the identifier PXD017578.

Quantitative LC-MS proteoform profiling of intact wheat glutenin subunits

Methodology for the quantitative analysis of intact glutenin proteins by ESI-LC-MS was developed with 1 Da mass resolution, constituting the first published application of proteoform profiling to plant biology. Two parent lines and 28 F5 crosses were analyzed in two blocks, 14 months apart. Control sample data were used to align retention times and normalize abundance between sample sets. A total of 4622 observations of 347 distinct proteoforms between 17 899 and 88 744 Da were observed. Proteoform abundances spanned a 1000-fold range and were linear (r2 > 0.990) with dilution. A novel method for the objective elimination of low intensity, noise-dominated data using replicate variability within the dataset is presented. Two abundant PTMs were detected; one known but uncharacterized Bx and Dy high-molecular-weight glutenin subunit (HMWGS) PTM and the other in 24 low molecular weight proteoform pairs. Finally, 16 abundant proteoforms were detected in progeny but not in either parent. This application should increase the statistical power of correlations between gluten complement and functional data and drive the detection of novel PTMs that may indicate differential regulation of the cellular processes related to quality.

Contributions of individual and combined Glu-B1x and Glu-B1y high-molecular-weight glutenin subunits to semolina functionality and pasta quality

Durum wheat is an important food crop used primarily for pasta production. High-molecular-weight glutenin subunits (HMW-GS) encoded by the closely linked genes Glu-B1x and Glu-B1y are known for their combined effects on pasta quality, but their individual contributions and interactions remain poorly understood. In this study, we show that individual loss-of-function mutants of Glu-B1x (ΔBx6) and Glu-B1y (ΔBy8) were associated with significant reductions in gluten strength compared to the wildtype, with stronger effects in the ΔBxy double mutant. Reductions in gluten strength were reflected in reduced mixograph and alveograph parameters, gluten index, faster extrusion flow rates and increased cooking loss. Interestingly, the Glu-B1x mutation was also associated with significant increases in grain and semolina protein content, increased pasta firmness, reduced starch viscosity and increased amylose in ΔBx6 and ΔBxy. In general, the ΔBx6 mutation had stronger effects than the ΔBy8 mutation, and significant interactions between the two genes were frequent. In addition to the basic knowledge gained on the individual effects of the Bx6 and By8 subunits and their interactions, the genetic stocks developed in this study provide useful tools to study the effects of natural or synthetic HMW-GS on pasta quality parameters in a background lacking endogenous HMW-GS.

Variation of Storage Proteins in Crimean Populations of Dasypyrum villosum

The objective of the investigation was to study variation of storage proteins in two Crimean populations of Dasypyrum villosum from Beregove of the Bakhchisarai region and from the Tauric Chersonese National Reserve (Sevastopol). Sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis of seed storage proteins was performed to analyze diversity of high-molecular-weight glutenin subunits encoded by the Glu-V1 locus, as well as ??-gliadin variants on SDS-electrophoregrams encoded by Gli-V1. In the two Crimean populations of D. villosum, eight alleles at the Glu-V1 locus and four Gli-V1 alleles encoding ??-gliadin were identified. The Crimean populations of D. villosum differed significantly in the frequencies of the alleles a, b, and c at the Glu-V1 locus and both had a high frequency of the null allele (k). The populations showed significant differences in frequencies of ??-gliadin variants on SDS-electrophoregrams encoded by Gli-V1, and gene diversity with respect to this marker was higher in the population of Beregove than that in the Chersonese population. ??-Gliadins on SDS-electrophoregrams are a convenient marker system for analysis of D. villosum populations, which can be employed simultaneously with analysis of high-molecular-weight glutenin subunits.

Effects of Seed-Applied Biofertilizers on Rhizosphere Biodiversity and Growth of Common Wheat (Triticum aestivum L.) in the Field.

In order to reduce chemical fertilization and improve the sustainability of common wheat (Triticum aestivum L.) cultivation, maintaining at the same time high production and quality standards, this study investigated the effects of three commercial biofertilizers on rhizosphere bacterial biomass, biodiversity and enzymatic activity, and on plant growth and grain yield in a field trial. The wheat seeds were inoculated with the following aiding microrganisms: (i) a bacterial consortium (Azospirillum spp. + Azoarcus spp. + Azorhizobium spp.); and two mycorrhizal fungal-bacterial consortia, viz. (ii) Rhizophagus irregularis + Azotobacter vinelandii, and (iii) R. irregularis + Bacillus megaterium + Frateuria aurantia, and comparisons were made with noninoculated controls. We demonstrate that all the biofertilizers significantly enhanced plant growth and nitrogen accumulation during stem elongation and heading, but this was translated into only small grain yield gains (+1%–4% vs controls). The total gluten content of the flour was not affected, but in general biofertilization significantly upregulated two high-quality protein subunits, i.e., the 81 kDa high-molecular-weight glutenin subunit and the 43.6 kDa low-molecular-weight glutenin subunit. These effects were associated with increases in the rhizosphere microbial biomass and the activity of enzymes such as β-glucosidase, α-mannosidase, β-mannosidase, and xylosidase, which are involved in organic matter decomposition, particularly when Rhizophagus irregularis was included as inoculant. No changes in microbial biodiversity were observed. Our results suggest that seed-applied biofertilizers may be effectively exploited in sustainable wheat cultivation without altering the biodiversity of the resident microbiome, but attention should be paid to the composition of the microbial consortia in order to maximize their benefits in crop cultivation.

Reducing the Immunogenic Potential of Wheat Flour: Silencing of Alpha Gliadin Genes in a U.S. Wheat Cultivar.

The alpha gliadins are a group of more than 20 proteins with very similar sequences that comprise about 15%–20% of the total flour protein and contribute to the functional properties of wheat flour dough. Some alpha gliadins also contain immunodominant epitopes that trigger celiac disease, a chronic autoimmune disease that affects approximately 1% of the worldwide population. In an attempt to reduce the immunogenic potential of wheat flour from the U.S. spring wheat cultivar Butte 86, RNA interference was used to silence a subset of alpha gliadin genes encoding proteins containing celiac disease epitopes. Two of the resulting transgenic lines were analyzed in detail by quantitative two-dimensional gel electrophoresis combined with tandem mass spectrometry. Although the RNA interference construct was designed to target only some alpha gliadin genes, all alpha gliadins were effectively silenced in the transgenic plants. In addition, some off-target silencing of high molecular weight glutenin subunits was detected in both transgenic lines. Compensatory effects were not observed within other gluten protein classes. Reactivities of IgG and IgA antibodies from a cohort of patients with celiac disease toward proteins from the transgenic lines were reduced significantly relative to the nontransgenic line. Both mixing properties and SDS sedimentation volumes suggested a decrease in dough strength in the transgenic lines when compared to the control. The data suggest that it will be difficult to selectively silence specific genes within families as complex as the wheat alpha gliadins. Nonetheless, it may be possible to reduce the immunogenic potential of the flour and still retain many of the functional properties essential for the utilization of wheat.

Absence of Dx2 at Glu-D1 Locus Weakens Gluten Quality Potentially Regulated by Expression of Nitrogen Metabolism Enzymes and Glutenin-Related Genes in Wheat.

Absence of high-molecular-weight glutenin subunit (HMW-GS) Dx2 weakens the gluten quality, but it is unclear how the absence of Dx2 has these effects. Thus, we investigated the gluten quality in terms of cytological, physicochemical, and transcriptional characteristics using two near-isogenic lines with Dx2 absent or present at Glu-D1 locus. Cytological observations showed that absence of Dx2 delayed and decreased the accumulation of protein bodies (PBs), where fewer and smaller PBs formed in the endosperm. The activity and gene expression levels of nitrogen assimilation and proteolysis enzymes were lower in HMW-D1a without Dx2 than HMW-D1p with Dx2, and thus less amino acid was transported for protein synthesis in the grains. The expression pattern of genes encoding Glu-1Dx2+1Dy12 was similar to those of three transcription factors, where these genes were significantly down-regulated in HMW-D1a than HMW-D1p. Three genes involving with glutenin polymerization were also down-regulated in HMW-D1a. These results may explain the changes in the glutenin and glutenin macropolymer (GMP) levels during grain development. Therefore, we suggest that the lower nitrogen metabolism capacity and expression levels of glutenin synthesis-related genes in HMW-D1a accounted for the lower accumulation of glutenin, GMP, and PBs, thereby weakening the structural‒thermal properties of gluten.

Allelic Variation for Prolamins in Spanish Durum Wheat Landraces and Its Relationship with Quality Traits

Wheat landraces are currently being explored mainly as a source of allelic variation related to crop resilience and low-input adaptation. Characterization of their high- and low-molecular weight glutenin subunits can aid breeders to select as donor local materials those ensuring good end-use properties in the derived elite cultivars. By using protein electrophoretic methods, we have determined the prolamin allelic profile of 116 Spanish durum wheat landraces. Their quality properties (as defined by grain protein content, sodium dodecyl sulfate (SDS) sedimentation volume and mixograph behavior) have also been assessed. The study has identified six novel glutenin alleles plus some other rare alleles some of which have been associated with improved durum wheat quality. Most of the novel variation detected needs to be characterized in a wider sample of varieties to establish any eventual beneficial effect on functional quality. Further analysis of the quality properties associated to specific allele combinations of Glu-A3, Glu-B3, and Glu-A1 has disclosed some clues on the influence on quality of certain non-allelic interactions between these main prolamin-encoding loci. Some of the landraces, showing outstanding values for the gluten quality parameters analyzed, might be directly used by farmers interested in the cultivation of traditional varieties for specialized food markets.

Soft wheat quality traits in Jiangsu province and their relationship with cookie making quality

The objectives of this study were to investigate soft wheat quality traits with fertilizer management practice in southern region of the Huaihe river in Jiangsu province, and to suggest quality selection parameters in soft wheat breeding. Fifteen high quality soft wheat varieties or advanced lines were grown at three environments with the combination of location and year. High-molecular-weight glutenin subunits (HWM-GS) of tested genotypes were identified. Kernel hardness, grain and flour protein content, wet gluten content, ash content, Zeleny sedimentation value, parameters of farinograph, mixograph, and rapid viscocity analysis (RVA), solvent retention capacity (SRC), gluten protein quantification, and cookie quality were investigated. No sample met the national soft wheat quality standard (GB/T 17320-2013, GB/T 17893-1999) for protein content, wet gluten content, and farinograph stability, few samples met the standard for sedimentation value, and all samples exceeded the standard for kernel hardness and farinograph absorption. Kernel hardness, ash content, and RVA parameters were not significantly associated with cookie quality parameters. Zeleny sedimentation value, absorption and stability of farinograph, peak time and right of peak slope of mixograph, water SRC, sodium carbonate SRC, lactic acid SRC, glutenin/gliadin ratio, unextractable polymeric protein (UPP), and %UPP were significantly correlated with cookie diameter, with r = –0.657, –0.601, –0.617, –0.659, –0.676, –0.857, –0.726, –0.616, –0.546, –0.541, and –0.637, respectively ( r ≤ –0.520, P r ≤ –0.652, P

Mass spectrometry of in-gel digests reveals differences in amino acid sequences of high-molecular-weight glutenin subunits in spelt and emmer compared to common wheat.

High-molecular-weight glutenin subunits (HMW-GS) play an important role for the baking quality of wheat. The ancient wheats emmer and spelt differ in their HMW-GS pattern compared to modern common wheat and this might be one reason for their comparatively poor baking quality. The aim of this study was to elucidate similarities and differences in the amino acid sequences of two 1Bx HMW-GS of common wheat, spelt and emmer. First, the sodium dodecyl polyacrylamide gel electrophoresis (SDS-PAGE) system was optimized to separate common wheat, spelt and emmer Bx6 and Bx7 from other HMW-GS (e.g., 1Ax and 1By) in high concentrations. The in-gel digests of the Bx6 and Bx7 bands were analyzed by untargeted LC-MS/MS experiments revealing different UniProtKB accessions in spelt and emmer compared to common wheat. The HMW-GS Bx6 and Bx7, respectively, of emmer and spelt showed differences in the amino acid sequences compared to those of common wheat. The identities of the peptide variations were confirmed by targeted LC-MS/MS. These peptides can be used to differentiate between Bx6 and Bx7 of spelt and emmer and Bx6 and Bx7 of common wheat. The findings should help to increase the reliability and curation status of wheat protein databases and to understand the effects of protein structure on the functional properties. Graphical abstract.

SNP markers for early identification of high molecular weight glutenin subunits (HMW-GSs) in bread wheat.

A set of eight SNP markers was developed to facilitate the early selection of HMW-GS alleles in breeding programmes. In bread wheat (Triticum aestivum), the high molecular weight glutenin subunits (HMW-GSs) are the most important determinants of technological quality. Known to be very diverse, HMW-GSs are encoded by the tightly linked genes Glu-1-1 and Glu-1-2. Alleles that improve the quality of dough have been identified. Up to now, sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) of grain proteins is the most widely used for their identification. To facilitate the early selection of HMW-GS alleles in breeding programmes, we developed DNA-based molecular markers. For each accession of a core collection (n = 364 lines) representative of worldwide bread wheat diversity, HMW-GSs were characterized by both genotyping and SDS-PAGE. Based on electrophoresis, we observed at least 8, 22 and 9 different alleles at the Glu-A1, Glu-B1 and Glu-D1 loci, respectively, including new variants. We designed a set of 17 single-nucleotide polymorphism (SNP) markers that were representative of the most frequent SDS-PAGE alleles at each locus. At Glu-A1 and Glu-D1, two and three marker-based haplotypes, respectively, captured the diversity of the SDS-PAGE alleles rather well. Discrepancies were found mainly for the Glu-B1 locus. However, statistical tests revealed that two markers at each Glu-B1 gene and their corresponding haplotypes were more significantly associated with the rheological properties of the dough than were the relevant SDS-PAGE alleles. To conclude, this study demonstrates that the SNP markers developed provide additional information on HMW-GS diversity. Two markers at Glu-A1, four at Glu-B1 and two at Glu-D1 constitute a useful toolbox for breeding wheat to improve end-use value.

Effect of wheat grain protein composition on end-use quality.

The quality of wheat products has been a new challenge next to wheat production which was achieved substantially during green revolution. The end-use quality of wheat is an essential factor for its commercial demand. The quality of wheat is largely based on the wheat storage proteins which extensively influences the dough properties. High molecular weight glutenin subunits (HMWGS), low molecular weight glutenin subunits (LMWGS) and gliadins significantly influence the end-use quality. Genomics and proteomics study of these gluten proteins of bread and durum wheat have explored new avenues for precise identification of the alleles and their role in end-use quality improvement. Secalin protein of Secale cereale encoded by Sec-1 loci and isassociated with 1RS.1BL translocation has been known for deterioration of end-use quality. Chromosomal manipulations using various approaches have led to the development of new recombinant lines of wheat without secalin. Advanced techniques associated with assessment of end-use quality have integrated the knowledge of useful or deteriorating HMWGS/LMWGS alleles and their potential role in end-use quality. This review gives a comprehensive insight of different aspects of the end-use quality perspective for bread making in wheat along with some information on the immunological interference of gluten in celiac disease.

Changes in Antioxidant System during Grain Development of Wheat (Triticum aestivum L.) and Relationship with Protein Composition under FHB Stress.

Fusarium head blight (FHB) is found in both temperate and semi-tropical regions and causes losses in wheat (Triticum aestivum L.) resulting in reduced yield, deteriorated grain quality, and contamination of the grains with mycotoxins, primarily deoxynivalenol (DON). In this study, we focused on the identification of protein components in Fusarium-inoculated and non-inoculated wheat samples along with the major antioxidant enzymes that Fusarium can encounter during FHB infection process in six winter wheat varieties when FHB symptoms started to occur. Our hypothesis was that wheat antioxidants and H2O2 may play a role against Fusarium infections, consequently preserving protein grain components. Results showed that in more resistant varieties (Olimpija and Vulkan) DON content of inoculated flour was less accumulated and thus the major gluten network was not significantly attacked by Fusarium spp. The maximum increase in guaiacol peroxidase (POD) activity in response to FHB treatment was detected in the FHB-resistant varieties Olimpija and Vulkan, while the lowest increase in H2O2 content was detected in the FHB-susceptible variety Golubica. A particular reduction in the content of both total glutenin and high-molecular-weight glutenin subunits was detected in susceptible wheat varieties after serious artificial infection, along with increased DON accumulation. The defense mechanism in wheat varieties differed, where resistant varieties’ protein composition depended on POD activity as a detoxification agent.

The overexpression of high-molecular-weight glutenin subunit Bx7 improves the dough rheological properties by altering secondary and micro-structures of wheat gluten.

Bread wheat (Triticum aestivum L.) is one of the crucial cereals consumed by human beings and wheat gluten, the natural macromolecules, mainly determines the processing quality of wheat dough. The high-molecular-weight glutenin subunits (HMW-GSs) of gluten proteins are recognized as one of the main components regulating the rheological properties of dough. The overexpressed Bx7 subunit (Bx7OE) has been reported to improve wheat quality and rheological properties of dough, however its effect on secondary and micro- structures of gluten is still unclear. In this study, we evaluated the composition of main storage proteins in wheat grains of two near-isogenic lines and studied the effect of Bx7 subunit expression level on the secondary structures of gluten and micro-structure of gluten during dough mixing process. Results showed the protein content, HMW-GSs proportion in total glutenins and free sulfhydryl content increased in the flour of HMW-Bx7OE wheat line, and the accumulation of unextractable polymeric protein during grain filling stage accelerated. It was found that the content of β-sheets in secondary structures of gluten increased and a more compact micro-structure of gluten network formed in the dough. Protein network analysis characterized and quantified the alterations in the gluten micro-structure. In the process of dough mixing, protein area, total protein length, number of junctions and branching rate reach the peak at dough development time, which was consistent with Chopin mixing profile. Interestingly, during dough mixing, the above-mentioned parameters of HMW-Bx7OE showed less changes than those of HMW-Bx7 wheat line, indicating Bx7OE improved the dough stability during mixing. To conclude, Bx7OE alters the secondary and micro- structures of gluten and thus improves the mixing and rheological properties of wheat dough.

The production of wheat – Aegilops sharonensis 1Ssh chromosome substitution lines harboring alien novel high-molecular-weight glutenin subunits

In our previous work, a novel high-molecular-weight glutenin subunit (HMW-GS) with an extremely large molecular weight from Aegilops sharonensis was identified that may contribute to excellent wheat (Triticum aestivum) processing quality and increased dough strength, and we further generated HMW-GS homozygous lines by crossing. In this study, we crossed the HMW-GS homozygous line 66-17-52 with 'Chinese Spring' Ph1 mutant CS ph1b to induce chromosome recombination between wheat and Ae. sharonensis. SDS-PAGE was used to identify 19 derived F2 lines with the HMW-GSs of Ae sharonensis. The results of non-denaturing fluorescence in situ hybridization (ND-FISH) indicated that lines 6-1 and 6-7 possessed a substitution of both 5D chromosomes by a pair of 1Ssh chromosomes. Further verification by newly developed 1Ssh-specific chromosome markers showed that these two lines amplified the expected fragment. Thus, it was concluded that lines 6-1 and 6-7 are 1Ssh(5D) chromosome substitution lines. The 1Ssh(5D) chromosome substitution lines, possessing alien subunits with satisfactory quality-associated structural features of large repetitive domains and increased number of subunits, may have great potential in strengthening the viscosity and elasticity of dough made from wheat flour. Therefore, these substitution lines can be used for wheat quality improvement and further production of 1Ssh translocation lines.

Change in physicochemical characteristics and molecular weight distribution of glutenin macropolymer induced by postharvest wheat maturation

The present study was aimed to investigate change in physicochemical characteristics and glutenin macropolymer (GMP) molecular weight distribution during postharvest wheat maturation. The freshly harvested wheat was stored under four different conditions (WT1, WT2, WT3 and WT4) for specified times. During maturation, the strengthening of wheat gluten structure was observed by increase in gluten index, swelling index of glutenin and sodium dodecyl sulphate (SDS) sedimentation value. The postharvest maturation resulted in contents increase of glutenin, glutenin/gliadin ratio, and GMP, and the decline of gliadin content. The contents of free sulfhydryl in GMP reduced, and S-S content rose during the whole maturation. Visible aggregates of GMP were observed in SDS-PAGE patterns for WT3 and WT4 samples after 4 weeks of storage. Moreover, in these two samples, polymerisation of gluten proteins into GMP was observed in size-exclusion high performance liquid chromatography patterns during storage. Some low molecular weight glutenin subunits (LMW-GS) incorporated into the aggregate, or combination of high molecular weight glutenin subunits and LMW-GS formed large polymeric glutenins by S-S linkage, and then assembled into GMP in postharvest wheat maturation. GMP polymerisation probably results in the improvement of wheat quality.