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

Development of a barley reference material for gluten analysis

Celiac disease (CD) can be triggered in susceptible individuals by the consumption of gluten, a complex storage protein mixture present in wheat, rye and barley. There is no specific reference material (RM) available for barley and this leads to inaccurate quantitation of barley gluten in supposedly gluten-free foods. Therefore, the aim was to select representative barley cultivars to establish a new barley RM. The relative protein composition of the 35 barley cultivars averaged 25% albumins and globulins, 11% d-hordeins, 19% C-hordeins, and 45% B/γ-hordeins. The mean gluten and protein content was 7.2 g/100 g and 11.2 g/100 g, respectively. The prolamin/glutelin ratio (1:1) commonly used in ELISAs to calculate the gluten content was found to be inappropriate for barley (1.6 ± 0.6). Eight cultivars suitable as potential RMs were selected to ensure a typical barley protein composition and improve food safety for CD patients.

Rapid and Easy High-Molecular-Weight Glutenin Subunit Identification System by Lab-on-a-Chip in Wheat (Triticum aestivum L.)

Lab-on-a-chip technology is an emerging and convenient system to easily and quickly separate proteins of high molecular weight. The current study established a high-molecular-weight glutenin subunit (HMW-GS) identification system using Lab-on-a-chip for three, six, and three of the allelic variations at the Glu-A1, Glu-B1, and Glu-D1 loci, respectively, which are commonly used in wheat breeding programs. The molecular weight of 1Ax1 and 1Ax2* encoded by Glu-A1 locus were of 200 kDa and 192 kDa and positioned below 1Dx subunits. The HMW-GS encoded by Glu-B1 locus were electrophoresed in the following order below 1Ax1 and 1Ax2*: 1Bx13 ≥ 1Bx7 = 1Bx7OE > 1Bx17 > 1By16 > 1By8 = 1By18 > 1By9. 1Dx2 and Dx5 showed around 4-kDa difference in their molecular weights, with 1Dy10 and 1Dy12 having 11-kDa difference, and were clearly differentiated on Lab-on-a-chip. Additionally, some of the HMW-GS, including 1By8, 1By18, and 1Dy10, having different theoretical molecular weights showed similar electrophoretic mobility patterns on Lab-on-a-chip. The relative protein amount of 1Bx7OE was two-fold higher than that of 1Bx7 or 1Dx5 and, therefore, translated a significant increase in the protein amount in 1Bx7OE. Similarly, the relative protein amounts of 8 & 10 and 10 & 18 were higher than each subunit taken alone. Therefore, this study suggests the established HMW-GS identification system using Lab-on-a-chip as a reliable approach for evaluating HMW-GS for wheat breeding programs.