Correspondence between two minor Glu-A3 genes of durum wheat and their encoded polypeptides by using a proteomic approach

The low molecular weight glutenin subunits (LMW-GS) are wheat storage proteins participating to the formation of glutenin polymers that, along with the other gluten proteins, allow the accumulation of a large quantity of protein in the endosperm tissue. The size and composition of the glutenin polymers are directly related to gluten visco-elastic properties. In particular, LMW-GS composition is the factor most influencing durum wheat quality.LMW-GS are composed of multiple polypeptides encoded by a gene family located at the orthologous Glu-3 loci. Due to the complex composition of this gene family, the direct correspondence between LMW-GS genes and their encoded products is very limited. Moreover, the abundance of LMW-GS hides the presence of less represented polypeptides. Here we report the characterization of the encoded polypeptides of two genes at the Glu-A3 locus. The LDNLMW1A1 gene encodes an LMW-i type glutenin subunit, whereas the LDNLMW1A3 codes for an LMW-m type with a peculiar N-terminal sequence. By using a proteomic comparison between the 2D electrophoretic patterns of the D-genome-chromosome substitution lines of cv. Langdon and the heterologously expressed LDNLMW1A1 and LDNLMW1A3, we show clear evidence of their expression in the endosperm tissue and their participation in the glutenin polymer.

► The high number and similarity of LMW-GS complicates their characterization.
► The direct correspondence between LMW-GS genes and encoded polypeptides is limited.
► Using combined methods we succeeded in attributing 2 1A-coded LMW-GS to their genes.
► One of the LMW-GS shows the N-terminal sequence MDTSC, first identified at protein level.