Wheat bread making (WBM)-like seed proteins (WSPN): A new family of small prolamins in barley

Abstract

Expression level of the gene Wheat Breadmaking (TaWBM) has been shown to be correlated with bread quality, and influences the rising of the bread loaf. We found that a family of the wbm homologous genes are present not only in wheat, but also in oat, rye and barley. However, a WBM protein has never been demonstrated experimentally. We have identified the existence of a family of WBM-like Seed Proteins (WSPN) from the prolamin fraction of barley flour, encoded by three closely linked genes on the long arm of chromosome 7H, analysing the gene expression by qPCR and relative protein levels by mass spectroscopy. All three genes are expressed specifically in seeds with no detectable expression in the leaves. The barley WSPNs share a common gene structure with a single exon containing an open reading frame in the size 253–313 bp, with the first 80 bp predicted by TargetP 2.0 to encode a sorting peptide. Furthermore, they all contain the conserved motif C–P-X-G-X4-C-X(4–8)-C-X-C. Structure prediction with Alphafold 2.0 suggest that this motif is a structurally conserved microdomain consisting of two antiparallel strands where the cysteines align.