Creating a balance - The incorporation of a HMW glutenin subunit into transgenic wheat lines

Transgenic wheat lines showing over-expression of HMW glutenin subunits provide useful tools to investigate the effects of changes in the ratio of x : y subunits on functional dough properties. Titration experiments were carried out to incorporate purified subunit 1Dy10 into transgenic lines showing over-expression of subunit 1Dx5 (B73-6-1 and B73-6-4) using a reduction-oxidation process. In all cases, the incorporation of subunit 1Dy10 decreased the Dx/Dy ratio and resulted in a weaker dough, as shown by a shorter mixing time and an increase in resistance breakdown. Flours of three lines (the normal lines L88-31, Olympic/Gabo and the transgenic line B72-8-11b), adjusted for equivalent protein content, glutenin/gliadin ratio and HMW/LMW glutenin ratios, were analysed in order to determine the functional importance of the ratio of Dx/Dy subunits. A similar experiment was carried out with the line B72-8-11b, but with the amount of Dy10 incorporated being adjusted to give the same Dx/Dy ratio as the Olympic/Gabo line. The creation of a balanced Dx/Dy ratio resulted in mixing curves with a broader BWPR. These results are consistent with the hypothesis that an appropriate ratio of x : y subunits is required for dough extensibility.