Varietal Differences in Mature Protein Composition of Wheat Resulted From Different Rates of Polymer Accumulation During Grain Filling

Abstract

Two varieties of wheat differing in high-molecular-weight glutenin subunit composition (Oxley, 2+12, Glu-D1a and Egret, 5+10, Glu-D1d) and dough properties were examined in order to determine the manner in which differences in mature protein composition were the result of differences in accumulation of proteins during grain filling. To this end, grain samples from each cultivar were taken at 5 day intervals from 10 days after anthesis to maturity, and analysed for protein content and composition. Wheat proteins were separated and quantified as albumin/globulin, monomer, SDS-soluble polymer and SDS-insoluble polymer using size-exclusion high-performance liquid chromatography. For both cultivars, the accumulation of each class of protein was found to be highly asynchronous: synthesis of albumin/globulin was followed by that of monomer, SDS-soluble polymer and finally SDS-insoluble polymer, such that the average molecular size of grain protein increased throughout grain filling. Varietal differences in mature protein composition were almost entirely the result of a greater rate of polymer accumulation in the 2+12 than in the 5+10 genotype.