Molecular cloning and functional characterization of two novel high molecular weight glutenin subunit genes in Aegilops markgrafii.

The high molecular weight glutenin subunits (HMW-GS) in bread wheat are major determinants of the viscoelastic properties of dough and the end-use quality of wheat flour. Two novel HMW-GSs, 1Cx1.1 and 1Cy9.1, from the diploid species Aegilops markgrafii (CC) were identified in the present study. The corresponding open-reading frames of the genes of 1Cx1.1 and 1Cy9.1 were isolated and sequenced using allele-specific polymerase chain reaction. Sequence comparison demonstrated that the HMW-GSs from Ae. markgrafii possess a similar primary structure to the homologous proteins in wheat and related species. A tandem tripeptide exists in the central repetitive domain of 1Cx1.1, and this unique structure is very rare in the HMW-GSs of other genomes. To confirm the authenticity of these isolated endogenous HMW-GS, the heterologous proteins produced by removing the signal peptides expressed by E. coli exhibited the same electrophoretic mobility as the native proteins. Subsequently, the single protein was purified at a sufficient scale for incorporation into flour to performsodium dodecyl sulphate (SDS) sedimentation testing. Notably, the SDS sedimentation volume was less with the addition of 1Cx1.1 than it was with 1Cy9.1.