Conformational differences between two wheat (Triticum aestivum) 'high-molecular-weight' glutenin subunits are due to a short region containing six amino acid differences (original) (raw)
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Journal of Food Science, 2007
ABSTRACT: Gluten proteins, representing the major protein fraction of the starchy endosperm, are predominantly responsible for the unique position of wheat amongst cereals. These form a continuous proteinaceous matrix in the cells of the mature dry grain and form a continuous viscoelastic network during the mixing process of dough development. These viscoelastic properties underline the utilization of wheat to prepare bread and other wheat flour based foodstuffs. One group of gluten proteins is glutenin, which consists of high molecular weight (HMW) and low molecular weight (LMW) subunits. The HMW glutenin subunits (HMW-GS) are particularly important for determining dough elasticity. The common wheat possesses 3 to 5 HMW subunits encoded at the Glu-1 loci on the long arms of group 1 chromosomes (1A, 1B, and 1D). The presence of certain HMW subunits is positively correlated with good bread-making quality. Glutamine-rich repetitive sequences that comprise the central part of the HMW subunits are actually responsible for the elastic properties due to extensive arrays of interchain hydrogen bonds. Genetic engineering can be used to manipulate the amount and composition of the HMW subunits, leading to either increased dough strength or more drastic changes in gluten structure and properties.
Low molecular weight glutenin subunit is one of the important quality elements in wheat (Triticum aestivum L.). Although considerable allelic variation has been identified, the functional properties of individual alleles at Glu-3 loci are less studied. In this work, we performed the first comprehensive study on the molecular characteristics and functional properties of the Glu-B3h gene using the wheat cultivar CB037B and its Glu-B3 deletion line CB037C. The results showed that the Glu-B3h deletion had no significant effects on plant morphological or yield traits, but resulted in a clear reduction in protein body number and size and main quality parameters, including inferior mixing property, dough strength, loaf volume, and score. Molecular characterization showed that the Glu-B3h gene consists of 1179 bp, and its encoded B-subunit has a longer repetitive domain and an increased number of α-helices, as well as higher expression, which could contribute to superior flour quality. The SNP-based allele-specific PCR markers designed for the Glu-B3h gene were developed and validated with bread wheat holding various alleles at Glu-B3 locus, which could effectively distinguish the Glu-B3h gene from others at the Glu-B3 locus, and have potential applications for wheat quality improvement through marker-assisted selection. Wheat (Triticum aestivum L.), one of the three major cereal crops in the world, is a critical source of energy and nutrients in the human diet and has excellent processing characteristics. Wheat dough is used to make various food products including bread, noodles, cakes, and biscuits 1. The seed storage proteins in wheat consist of monomeric gliadins and polymeric glutenins that determine the extensibility and elasticity of dough, respectively 2,3. According to their mobility, as determined by sodium dodecyl sulfate polyacrylamide gel electropho-resis (SDS-PAGE), polymeric glutenins are subdivided into high and low molecular weight glutenin subunits (HMW-GS and LMW-GS, respectively), of which, LMW-GS accounts for ~60% of the glutenins and primarily determines dough strength and viscosity, thus playing a significant role in flour processing quality 4,5. Some studies have shown that the effects of LMW-GS on both dough resistance and dough extensibility are more favorable than the effects of HMW-GS 6,7. LMW-GS is encoded by Glu-A3, Glu-B3, and Glu-D3 loci on the short arms of chromosomes 1 A, 1B, and 1D, respectively, and these loci are linked to the Gli-1 locus, encoding gliadins 2,8. The molecular structure of LMW-GS contains four typical regions: (1) a signal peptide containing 20 amino acids removed in the maturation process, (2) a short N-terminal region with 13 amino acids containing one cysteine, (3) a repetitive domain rich with glu-tamine containing 70–186 amino acids as the variable region of gene size, and (4) a C-terminus rich with cysteine and glutamine. The C-terminus has three regions: (1) a cysteine-rich structure containing five cysteines, (2) a domain rich with glutamine, with only one cysteine and some tandem glutamines, and (3) a conserved region of the C-terminus with the last cysteine 9,10,11 .
Dough rheology of wheat recombinant lines in relation to allelic variants of Glu-1 and Glu-3 loci
Cereal Research Communications, 2011
Gliadins and glutenins of high and low molecular weight (HMWG and LMWG) are the genetic component, defining to certain degree dough strength and extensibility (rheology). The objective of the present study was to evaluate the effect of HMWG and LMWG combinations on gluten rheology of 98 F 6 lines, obtained from Rebeca F2000 × Verano S91 and Gálvez M87 × Bacanora T88 and progenitors. The genotypes were sown at Roque, state of Guanajuato, in the springsummer cycle 2008. In flour samples, variables associated with strength and extensibility of dough were assessed in mixograph (kneading time, kneading stability, tolerance to over-kneading) and Chopin alveograph (general strength of the dough, W and elasticity-extensibility relationship, P/L). In order to conduct analysis, progenies were grouped according to HMWG and LMWG combinations. In the cross Rebeca F2000 × Verano S91, combination Glu-1: 2*, 17+18, 5+10 with Glu-3: c, h, b was described by having half-strong and extensible gluten, which also described the combination of Rebeca F2000 (1, 17+18, 5+10, c, g, b). The combination 2*, 17+18, 2+12, e, g, b of the recombinant lines similar to Verano S91 were grouped as weak and extensible gluten. The recombinant combinations derived from the cross Gálvez M87 × Bacanora T88 were classified as of half-strong to strong and extensible gluten by its W and P/L. Combination 1, 17+18, 5+10 b, h, c, which corresponds to Gálvez M87 was the one of greatest dough strength. Combination 1, 7+9, 5+10, c, j, c, showed favorable gluten properties despite presence of translocation 1B/1R, which indicates that it is possible to reduce its negative effect through plant improvement. It is concluded that there are specific HMWG and LMWG combinations that favor dough quality (strength and extensibility).
Protein Composition for Pairs of Wheat Lines with Contrasting Dough Extensibility
Journal of Cereal Science, 1999
Factors determining dough extensibility have been studied using two pairs of advanced breeding lines grown at five different locations in which individual lines of each pair differed in extensibility. For one pair (DD118 and RAC704), the differences related mainly to variations in the percentage of flour polymeric protein. On the other hand, the second pair (VF304 and RAC746) did not show a significant difference in this parameter, making them suitable for the study of other factor(s) that influence extensibility, presumably genotypic in nature. The percentage of unextractable polymeric protein (UPP) differed appreciably between these two lines at all sites. This suggests that an important genotypic factor associated with extensibility is the molecular weight distribution of the protein.
Wheat glutenin subunits and dough elasticity: findings of the EUROWHEAT project
Trends in Food Science & Technology, 2000
Detailed studies of wheat glutenin subunits have provided novel details of their molecular structures and interactions which allow the development of a model to explain their role in determining the visco-elastic properties of gluten and dough. The construction and analysis of near-isogenic and transgenic lines expressing novel subunit combinations or increased amounts of specific subunits allows differences in gluten properties to be related to the structures and properties of individual subunits, with potential benefits for the production of cultivars with improved properties for food processing or novel end users #
Journal of Cereal Science, 1997
We report the construction of modified high M r glutenin subunit genes with variable lengths of the repetitive domain and their expression in Escherichia coli. The modified glutenin subunits showed anomalously slow migration by SDS-PAGE characteristic of these polypeptides. Changes in the size of the repetitive domain correlated with both the migration behaviour on SDS-PAGE and with the surface hydrophobicities of the polypeptides measured by RP-HPLC. These constructs made it possible to obtain direct evidence for the first time that the anomalous electrophoretic mobilities of high M r glutenin subunits in SDS-PAGE, compared with globular proteins, are mainly due to the repetitive domain. These constructs should be useful for establishing the role of the repetitive domain of high M r glutenin subunits in determining the viscoelastic properties of dough. They also offer the possibility of creating new genetic variability for wheat improvement.
Journal of Cereal Science, 1995
Polymeric protein plays a critical role in governing the functional properties of wheat flour. Wheat genetic fines lacking high Mr and, similarly, low Mr glutenin subunits from one, two or all three Glu-1 or Glu-3 loci, respectively, were thus used to investigate the effects of these polypeptides on glutenin polymer formation and dough/gluten properties. Polymer formation (quantity, size distribution) was studied by size-exclusion highperformance liquid chromatography (SE-HPLC) using extractable, unextractable and total protein from flour, as well as by diagonal electrophoresis using total protein extracts. The loss of Glu-1 or Glu-3 subunits had significant effects on the quantity of total, extractable and unextractable polymeric protein and on the dough and gluten properties of these fines. Dough and gluten properties were significantly correlated with the proportions of both total and tmextractable polymers (a measure of the relative molecular size distribution of polymeric protein), although more strongly with the proportions ofunextractable polymers in the case of Glu-1 null fines. The proportion of total polymeric protein decreased more markedly when all the Glu-3 subunits were deleted than when all the Glu-1 subunits were absent, which was in accordance with the relative quantities of these two types of the subunits in the grains. In contrast, loss of all the Glu-1 subunits, on an equal weight basis, reduced the amounts of the larger polymers to a much greater extent than the loss of all the Glu-3 subunits, reflecting more than the molecular size differences in these subunits. SE-HPLC and diagonal electrophoresis of total protein extracts from the triple Ghl-1 and Glu-3 null lines also revealed that Glu-1 or Ghl-3 subunits form large polymers on their own. When both high and low Mr glutenin subunits were present together, however, the amount of large polymer was much greater than the sum of the amounts when only one group was present, suggesting a positive interaction between these two groups ofsubunits with respect to polymer formation.
1998
Both high-and low-molecular-weight glutenin subunits (LMW-GS) play the major role in determining the viscoelastic properties of wheat (Triticum aestivum L.) flour. To date there has been no clear correspondence between the amino acid sequences of LMW-GS derived from DNA sequencing and those of actual LMW-GS present in the endosperm. We have characterized a particular LMW-GS from hexaploid bread wheat, a major component of the glutenin polymer, which we call the 42K LMW-GS, and have isolated and sequenced the putative corresponding gene. Extensive amino acid sequences obtained directly for this 42K LMW-GS indicate correspondence between this protein and the putative corresponding gene. This subunit did not show a cysteine (Cys) at position 5, in contrast to what has frequently been reported for nucleotide-based sequences of LMW-GS. This Cys has been replaced by one occurring in the repeated-sequence domain, leaving the total number of Cys residues in the molecule the same as in various other LMW-GS. On the basis of the deduced amino acid sequence and literature-based assignment of disulfide linkages, a computer-generated molecular model of the 42K subunit was constructed.
Proteomic analysis of wheat recombinant inbred lines: Variations in prolamin and dough rheology
Journal of Cereal Science, 2008
To investigate the impact of the 1BL.1RS translocation on dough strength and to understand how 1BL.1RS genotypes may overcome the loss of Glu-B3 and Gli-B1, proteomic profiles of 16 doubled haploid (DH) lines of similar glutenin composition but of different strength, as measured by Chopin's alveograph, were compared. The results showed that 32 spots, mainly prolamins, were differentially expressed and that five others were specific to high-strength DH lines. The identification and quantification of the prolamin fractions on the two-dimensional (2D) electrophoresis gels demonstrated that the high-molecular weight glutenin sub-unit (HMW-GS) were upregulated by 25% in 1BL.1RS DH lines, even though the corresponding genes were not located on the missing 1BS chromosome. The g-gliadins were also up-regulated (by 36%) in such lines to counterbalance, to some extent, the loss of LMW-GS of Glu-B3. The polymeric prolamin fractions also accumulated in high-tenacity lines and decreased in high-extensibility lines confirming the role of the inter-chain disulfide bonds in resistance to deformation. In contrast, the monomeric fraction of a-gliadin favored extensibility and decreased tenacity by increasing the accumulation (+12%) of a-gliadins in high-extensibility lines; the Gli-A1 allele of the parent Toronit was found to be more abundant when compared to the Gli-A1 allele of parent 211.12014.
2011
Gliadins and glutenins of high and low molecular weight (HMWG and LMWG) are the genetic component, defining to certain degree dough strength and extensibility (rheology). The objective of the present study was to evaluate the effect of HMWG and LMWG combinations on gluten rheology of 98 F 6 lines, obtained from Rebeca F2000 × Verano S91 and Gálvez M87 × Bacanora T88 and progenitors. The genotypes were sown at Roque, state of Guanajuato, in the springsummer cycle 2008. In flour samples, variables associated with strength and extensibility of dough were assessed in mixograph (kneading time, kneading stability, tolerance to over-kneading) and Chopin alveograph (general strength of the dough, W and elasticity-extensibility relationship, P/L). In order to conduct analysis, progenies were grouped according to HMWG and LMWG combinations. In the cross Rebeca F2000 × Verano S91, combination Glu-1: 2*, 17+18, 5+10 with Glu-3: c, h, b was described by having half-strong and extensible gluten, which also described the combination of Rebeca F2000 (1, 17+18, 5+10, c, g, b). The combination 2*, 17+18, 2+12, e, g, b of the recombinant lines similar to Verano S91 were grouped as weak and extensible gluten. The recombinant combinations derived from the cross Gálvez M87 × Bacanora T88 were classified as of half-strong to strong and extensible gluten by its W and P/L. Combination 1, 17+18, 5+10 b, h, c, which corresponds to Gálvez M87 was the one of greatest dough strength. Combination 1, 7+9, 5+10, c, j, c, showed favorable gluten properties despite presence of translocation 1B/1R, which indicates that it is possible to reduce its negative effect through plant improvement. It is concluded that there are specific HMWG and LMWG combinations that favor dough quality (strength and extensibility).