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 quali ty and quantity of high molecular weight (HMW) glutenins present in wheat f lour. We have produced several transgenic wheat lines expressing the high m olecular 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 trails and flour functionality in R4 see ds obtained from plants grown in the field. The expression of 1Ax1 in R4 se eds 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 it s own promoter was stable under field conditions. Quantitative differences were observed in gliadins, flour yield and single kernel characteristics be tween 1Ax1 transgenic wheat and the Bobwhite control. No qualitative differ ences in the gliadin or low molecular weight glutenin subunits were seen be tween the control and transgenic plants. Two of the transgenic lines showed some very high molecular weight proteins in addition to the 1Ax1 and the n ative HMW-GS. Purification and N-terminal sequencing of these proteins did not reveal any similarity to HMW-GS. In some of the transgenic lines, mixin g time, loaf volume and water absorbance improved relative to the control c ultivar. This was the first large scale baking and mixing test of field gro wn 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 undesira ble effect on yield, protein composition or flour functionality.