Partial C-terminal truncation of Bx and Dy high molecular weight glutenin subunits after conserved aspartate

Abstract

The composition of polymeric gluten proteins and interaction with non-covalently associated gliadins define the functional utility of a flour. This composition is dictated by the timing of cellular and genetic events in the plant and the developing seed. This interplay and its effect on gluten functionality is poorly understood and could provide a new opportunity for improving wheat quality in the future. Truncated proteoforms of high-molecular weight glutenin subunits (HMWGS) were observed for Bx and Dy subtypes across 49 Canadian bread wheat and 16 durum varieties. The relative abundances of these variants ranged from 7.5% to 37.7% and abundances of Bx and Dy variants were highly correlated (r2 = 0.85). HMWGS Bx7* and Dy10 were purified and the mass difference was shown to be from the loss of a C-terminal hexapeptide after a conserved aspartate residue. This aspartate was present at the ω-7 position in >90% of HMWGS accessions and the C-terminal sequence was highly conserved. Importantly, all HMWGS subtypes contain the same conserved sequences, but truncated variants were never observed for By, Dx and Ax HMWGS. The potential impact of these truncated HMWGS on gluten form and function is discussed.