Evaluation of baking properties and gluten protein composition of field grown transgenic wheat lines expressing high molecular weight glutenin gene 1Ax1

The unique breadmaking properties of wheat are closely related to the quality and quantity of high molecular weight (HMW) glutenins present in wheat flour. We have produced several transgenic wheat lines expressing the high molecular weight glutenin subunit (HMW-GS) gene 1Ax1. They were analyzed for stability of gene expression and the effect of over-expressed 1Ax1 protein on protein composition, agronomic traits and flour functionality in R4 seeds obtained from plants grown in the field. The expression of 1Ax1 in R4 seeds was similar to that found in R3 seeds harvested from plants reared in a growth chamber, indicating that the high level expression of 1Ax1 under its own promoter was stable under field conditions. Quantitative differences were observed in gliadins, flour yield and single kernel characteristics between 1Ax1 transgenic wheat and the Bobwhite control. No qualitative differences in the gliadin or low molecular weight glutenin subunits were seen between the control and transgenic plants. Two of the transgenic lines showed some very high molecular weight proteins in addition to the 1Ax1 and the native HMW-GS. Purification and N-terminal sequencing of these proteins did not reveal any similarity to HMW-GS. In some of the transgenic lines, mixing time, loaf volume and water absorbance improved relative to the control cultivar. This was the first large scale baking and mixing test of field grown transgenic wheat. Our results show that the integration of a seventh HMW-GS gene (1Ax1), and its expression resulting in the presence of six HMW-GS in the wheat endosperm, neither caused any gene silencing nor any undesirable effect on yield, protein composition or flour functionality.