Molecular characterization of the novel Glu-Ax1* gene of the high molecular weight gluten subunit from wild emmer wheat

The molecular composition of high-molecular-weight glutenin subunits (HMW-GS) plays a pivotal role in determining the processing quality of wheat flour. Utilizing the germplasm resources of wild wheat relatives to explore novel HMW-GS genes is crucial for wheat quality breeding and improvement. In this study, the Glu-Ax1* gene of HMW-GS was cloned from wild emmer wheat accession TD-129, which exhibits strong dough rheological properties, using directed deletion subcloning. The open reading frame (ORF) of the Glu-Ax1* gene was 2,523 bp and showed 98% sequence similarity with the known Triticeae HMW-GS genes. Comparative analysis of the amino acid sequence with published Glu-Ax subunits revealed that the Glu-Ax1* subunit contained an additional nine-peptide insertion (PTQGQQGQQ) in the central repeat region. Furthermore, this subunit possessed the highest glutamine (Q) content observed to date (289 residues). Secondary structure prediction indicated that the Glu-Ax1* subunit comprised nine elements, seven α-helices and two β-strands. The extended polypeptide length, elevated glutamines (Q) content and the increased number of predicted secondary structures suggest that the Glu-Ax1* subunit may positively influence bread making qualities. This novel Glu-Ax1* gene identified in wild emmer wheat accession TD-129 provides valuable genetic resources for the improvement of Glu-Ax locus in common wheat.