HMW-GS composition and rye translocations of U.S. eastern soft winter wheat and their associations with protein strength

Influence of High-Molecular-Weight Glutenin Subunit on Components and Multiscale Structure of Gluten and Dough Quality in Soft Wheat

A set of high-molecular-weight glutenin subunit (HMW-GS) deletion lines were used to investigate the influences of HMW-GS on wheat gluten, and dough properties were investigated using a set of HMW-GS deletion lines. Results showed that HMW-GS deletion significantly decreased the dough stability time, as well as viscoelastic moduli (G' and G″), compared with the wild type, where the deletion of x-type HMW-GSs (Ax1d, Bx7d, and Dy12d) decreased more than y-type HMW-GSs (By8d and Dy12d). The deletion of HMW-GS significantly decreased HMW-GS contents and increased α-/γ-gliadin contents. A proteomic study showed that the HMW-GS deletion down-regulated the HMW-GS, β-amylase, serpins, and protein disulfide isomerase and up-regulated the LMW-GS, α/γ-gliadin, and α-amylase inhibitor. Meanwhile, HMW-GS deletion significantly decreased contents of β-turn and β-sheet. In addition, less energetically stable disulfide conformations (trans-gauche-gauche and trans-gauche-trans) were abundant in HMW-GS deletion lines. Furthermore, analysis of five HMW-GSs based on amino acid sequences proved that Dx2 and Bx7 had a more stable structure, followed by Ax1, then Dy12, and finally By8.

Transcriptome and Proteome Analysis Revealed the Influence of High-Molecular-Weight Glutenin Subunits (HMW-GSs) Deficiency on Expression of Storage Substances and the Potential Regulatory Mechanism of HMW-GSs

The processing quality of wheat is affected by seed storage substances, such as protein and starch. High-molecular-weight glutenin subunits (HMW-GSs) are the major components of wheat seed storage proteins (SSPs); they are also key determinators of wheat end-use quality. However, the effects of HMW-GSs absence on the expression of other storage substances and the regulation mechanism of HMW-GSs are still limited. Previously, a wheat transgenic line LH-11 with complete deletions of HMW-GSs was obtained through introducing an exogenous gene Glu-1E^bx to the wild-type cultivar Bobwhite by transgenic approach. In this study, comparative seed transcriptomics and proteomics of transgenic and non-transgenic lines at different seed developmental stages were carried out to explore the changes in genes and proteins and the underlying regulatory mechanism. Results revealed that a number of genes, including genes related to SSPs, carbohydrates metabolism, amino acids metabolism, transcription, translation, and protein process were differentially enriched. Seed storage proteins displayed differential expression patterns between the transgenic and non-transgenic line, a major rise in the expression levels of gliadins were observed at 21 and 28 days post anthesis (DPA) in the transgenic line. Changes in expressions of low-molecular-weight glutenins (LMW-GSs), avenin-like proteins (ALPs), lipid transfer proteins (LTPs), and protease inhibitors (PIs) were also observed. In addition, genes related to carbohydrate metabolism were differentially expressed, which probably leads to a difference in starch component and deposition. A list of gene categories participating in the accumulation of SSPs was proposed according to the transcriptome and proteome data. Six genes from the MYB and eight genes from the NAC transcription families are likely important regulators of HMW-GSs accumulation. This study will provide data support for understanding the regulatory network of wheat storage substances. The screened candidate genes can lay a foundation for further research on the regulation mechanism of HMW-GSs.

Study of Noodle Quality Based on Protein Properties of Three Wheat Varieties

Waxy wheat offers unique benefits in food processing, including improving the smoothness and performance of the product. However, waxy wheat is not yet commercially available. The protein characteristics, including the protein content, subunit distribution, secondary structure, chemical interactions, and microstructure of the gluten, were explored to realize the full potential of waxy wheat. The results showed that the noodles prepared from waxy wheat had a gentle and glutinous texture compared with GY2018 and YM13. Partial-waxy and waxy wheat had a lower gluten index and glutenin macropolymer (GMP) content than GY2018, indicating a reduced gluten strength. Confocal laser scanning microscopy (CLSM) images showed that the starch granules were not securely attached to the partial-waxy and waxy wheat protein matrix. In addition, the waxy protein chains appeared more elongated and they weakened the protein network. In particular, HMW-GS subunit 2 + 12 may be the essential cause of the weak dough from SKN1. Compared with GY2018 and YM13, SKN1 had the highest number of free sulfhydryl groups. Rather than ionic bonds, hydrophobic interactions increased the gluten network in GY2018, YM13, and SKN1. The weak molecular forces in the gluten will result in a soft noodle texture.

Macromolecular networks interactions in wheat flour dough matrices during sequential thermal-mechanical treatment

Differences in Mixolab measurements of dough processing were examined using, as a base, flour from pure breeding, isogenic, wheat lines carrying either the high molecular weight glutenin subunits 5 + 10 or 2 + 12. Before dough pasting, subunits 5 + 10 tend to form a stable gluten network relying mainly on disulfide bonds and hydrogen bonds, but 2 + 12 flour was prone to generating fragile protein aggregates dominated by disulfide bonds and hydrophobicity. During dough pasting, a broader protein network rich in un-extractable polymeric proteins, disulfide bonds and β-sheets was formed in the dough with subunits 5 + 10, thus resulting in an extensive and compact protein-starch complex which was characterized by high thermal stability and low starch gelatinization, while in the dough of the 2 + 12 line, a porous protein-starch gel with fragmented protein aggregates was controlled by the combination of disulfide bonds, hydrophobicity and hydrogen bonds that facilitated the formation of antiparallel β-sheets.

Influences of high-molecular-weight glutenin subunits and rye translocations on dough-mixing properties and sugar-snap cookie-baking quality of soft winter wheat

BACKGROUND

The significance of high-molecular-weight glutenin subunits (HMW-GSs) and rye translocations, and their associations with gluten strength for hard wheat used for making bread has been understood well, but remains poorly understood for soft wheat used for making cookies. The influences of HMW-GSs and rye translocations on the dough-mixing properties and cookie-baking quality of soft wheat were investigated using 50 US eastern soft winter (ESW) wheat varieties possessing 14 predominant HMW-GS profiles.

RESULTS

Glu-A1 and Glu-B1 loci only influenced dough-mixing properties significantly, whereas the Glu-D1 locus influenced both dough-mixing properties and cookie-baking quality significantly. The subunits 1, 7* + 8 and 5 + 10 at the Glu-A1, Glu-B1 and Glu-D1 loci, respectively, were associated with a long midline peak time, whereas only the rare subunits 2 + 12₁ at the Glu-D1 locus exhibited significant associations with improved cookie-baking quality of ESW wheat. The contributions of rye translocations to dough-mixing properties and cookie-baking quality depended on HMW-GS profiles. Three HMW-GS profiles (2*, 7 + 9, 2 + 12₁ ), (2*, 7 + 8, 2 + 12₁ ) and (1, 7 + 8, 2 + 12₁ ) were identified as being desirable for making large-diameter cookies. Flour protein content, lactic acid (LA), and sodium carbonate (SC) solvent retention capacities and softness equivalence were identified as effective predictors of cookie diameter and accounted for 79% of the variation in cookie diameter.

CONCLUSION

Subunits 2 + 12₁ have significant associations with the protein characteristics and cookie-baking quality of soft wheat. The determination of HMW-GS composition would be an effective tool in soft-wheat breeding programs for quickly identifying and selecting acceptable breeding lines possessing desirable cookie-baking potential. Published 2020. This article is a U.S. Government work and is in the public domain in the USA.