Silencing of HMW glutenins in transgenic wheat expressing extra HMW subunits

Abstract 

Wheat HMW glutenin subunit genes 1Ax1 and 1Dx5 were introduced, and either expressed or overexpressed, into a commercial wheat cultivar that already expresses five subunits. Six independent transgenic events were obtained and characterized by SDS-PAGE and Southern analysis. The 1Dx5 gene was overexpressed in two events without changes in the other endosperm proteins. Overexpression of 1Dx5 increased the contribution of HMW glutenin subunits to total protein up to 22%. Two events express the 1Ax1 subunit transgene with associated silencing of the 1Ax2* endogenous subunit. In the SDS-PAGE one of them shows a new HMW glutenin band of an apparent M_r lower than that of the 1Dx5 subunit. Southern analysis of the four events confirmed transformation and suggest that the transgenes are present in a low copy number. Silencing of all the HMW glutenin subunits was observed in two different events of transgenic wheat expressing the 1Ax1 subunit transgene and overexpressing the Dx5 gene. Transgenes and expression patterns were stably transmitted to the progenies in all the events except one where in some of the segregating T₂ seeds the silencing of all HMW glutenin subunits was reverted associated with a drastic lost of transgenes from a high to a low copy number. The revertant T₂ seeds expressed the five endogenous subunits plus the 1Ax1 transgene.