Endosperm Proteins

Characterization of proteins from grain of different bread and durum wheat genotypes

The classical Osborne wheat protein fractions (albumins, globulins, gliadins, and glutenins), as well as several proteins from each of the four subunits of gliadin using SDS-PAGE analyses, were determined in the grain of five bread (T. aestivum L.) and five durum wheat (T. durum Desf.) genotypes. In addition, content of tryptophan and wet gluten were analyzed. Gliadins and glutenins comprise from 58.17% to 65.27% and 56.25% to 64.48% of total proteins and as such account for both quantity and quality of the bread and durum wheat grain proteins, respectively. The ratio of gliadin/total glutenin varied from 0.49 to 1.01 and 0.57 to 1.06 among the bread and durum genotypes, respectively. According to SDS-PAGE analysis, bread wheat genotypes had a higher concentration of α + β + γ-subunits of gliadin (on average 61.54% of extractable proteins) than durum wheat (on average 55.32% of extractable proteins). However, low concentration of ω-subunit was found in both bread (0.50% to 2.53% of extractable proteins) and durum (3.65% to 6.99% of extractable proteins) wheat genotypes. On average, durum wheat contained significantly higher amounts of tryptophan and wet gluten (0.163% dry weight (d.w.) and 26.96% d.w., respectively) than bread wheat (0.147% d.w. and 24.18% d.w., respectively).

Chromosomal location of genes coding for endosperm proteins of Hordeum chilense, determined by two-dimensional electrophoresis of wheat-H. chilense chromosome addition lines

The proteins of Hordeum chilense grain were resolved into 25 major components by two-dimensional electrophoresis. Their solubilities in aqueous alcohol solutions were determined to distinguish prolamin storage proteins from metabolic and structural proteins. The prolamins were divided into two groups, based on the presence or absence of intermolecular disulfide bonds determined by gel-filtration chromatography. Using an incomplete set of Chinese Spring wheat-H. chilense disomic addition lines, the structural genes of 21 of the 26 most dominant seed proteins were assigned to chromosomes. The great majority of the prolamin genes, including those coding for a high molecular weight (HMW) prolamin subunit, was present on chromosome 1 Hch. However, a small number of prolamin genes also occurred on chromosomes 5 Hch and 7 Hch. A minor protein, probably belonging to the nonstorage group of proteins, is coded by genes on 5 Hch. Various ditelosomic addition lines and ditelosomic and disomic substitution lines for chromosome 7 Hch were also analyzed by electrophoresis. This technique revealed that the genes for three major prolamins occur on the beta arm of chromosome 7 Hch and that a gene for a minor protein, also thought to be a prolamin, occurs on the alpha arm. These results are discussed in relation to the evolution of prolamin genes in the Triticeae.