Structure and Quantitative-Structure-Function Relationships of Wheat High-Molecular-Weight Glutenin Subunits: From...

High-molecular-weight glutenin subunits (HMW-GSs) form the structural backbone of the wheat gluten network, and their compositional and structural polymorphisms strongly shape dough rheological properties. As wheat processing becomes increasingly standardized and specialized, the requirements for dough properties, especially strength and extensibility, are becoming more stringent and diverse. This makes it essential to clarify the structure-function and dose-effect relationships between HMW-GS and dough rheological properties. On the basis of current evidence, this review focuses on three main aspects: (1) the contributions of HMW-GS allelic variation to dough strength and extensibility; (2) the molecular mechanisms by which multidimensional structural features of HMW-GSs determine these rheological traits; and (3) the relationships between multidimensional structural polymorphism and dough strength and extensibility. Subunits, such as Ax1, Ax2*, Bx14 + By15, and Bx17 + By18, can synergistically enhance both strength and extensibility, whereas Bx7^OE + By8 and Dx5+Dy10 generally enhance strength at the expense of extensibility. We propose a multidimensional structure-function framework in which "loop-train" motifs and helical conformations confer elasticity; disulfide bonds cross-link elastic units into a gluten network; and non-covalent interactions (e.g., hydrogen bonding, hydrophobic, and ionic interactions) cooperate to build and stabilize the network. Single amino-acid substitutions at key residues can shift dough properties by altering local conformations and intermolecular interactions, including cysteine substitutions (e.g., Cys10Ser-N, Cys40Ser-N, Ser8Cys-central repetitive domain [CRD], Tyr612Cys-CRD, and Cys25Ser-N) and non-cysteine substitutions (e.g., Gly244Glu-CRD for Ax1). However, reported sequence polymorphisms-rheological traits remain difficult to reconcile with large-scale sequence datasets, and systematic analyses of higher order structural polymorphisms remain limited. Future work should resolve these gaps to enable more precise quality control and rational design of wheat-based products.