Jean-Claude Autran

Chromosome 1B-encoded gliadins and glutenin subunits in durum wheat: genetics and relationship to gluten strength

The progenies of crosses between Berillo and four durum wheat cultivars were analysed for storage protein composition (by four different electrophoresis procedures), genetic segregation and gluten quality (by SDS sedimentation test and Viscoelastograph). The crosses enabled the segregation patterns of alleles at Gli-B1, Glu-B3 and Glu-B1 on chromosome 1B, and at Gli-A2 on chromosome 6A to be determined. The gene order on chromosome 1B was deduced to be Glu-B1-centromere-Glu-B3-Gli-B1, with 47% recombination between Glu-B1 and Glu-B3, and 2% between Glu-B3 and Gli-B1. Genes coding for γ-gliadins at Gli-B1 were distal to ω-gliadin genes with respect to the centromere. Analyses of the progeny (F4 grains) from single F2 plants, indicated that gliadins γ-42 and γ-45 are only genetic markers of quality, whereas allelic variation for low molecular weight (LMW) glutenin subunits encoded at the Glu-B3 locus is primarily responsible for differences in SDS sedimentation volume and gluten viscoelastic properties. High molecular weight (HMW) glutenin subunits 7+8 also gave larger SDS sedimentation volumes and higher gluten elastic recoveries than subunits 6+8 and 20. The positive effects of the so-called LMW-2 glutenin subunits and HMW subunits 7+8 were additive, with LMW-2 being the most important proteins for pasta-making quality as evaluated by SDS-sedimentation and gluten viscoelasticity (both parameters related to firmness of cooked pasta). Two alleles at Gli-A2 coding for α-gliadins were also found to have different effects on gluten firmness.

Genetic analysis of low Mr glutenin subunits fractionated by two-dimensional electrophoresis (A-PAGE × SDS-PAGE)

Alkylated glutenin subunits of F7 progenies from the cross between the Italian bread wheat cultivar Costantino and the Canadian cultivar Neepawa were fractionated by one-dimensional A-PAGE and SDS-PAGE and by two-dimensional A-PAGE × SDS-PAGE. Each gliadin allele at the Gli-1 loci of the parental cultivars was shown to be associated with a specific allele at each of the Glu-3 loci, at which low Mr glutenin subunits are encoded. The Glu-A3 locus was found to code for two low Mr subunits in Neepawa and three in Costantino. In this latter cultivar, eight low Mr subunits were assigned to each of the Glu-B3 and Glu-D3 loci, whereas seven subunits were attributed to the Glu-B3 locus and seven to the Glu-D3 locus in Neepawa. A-PAGE × SDS-PAGE can be employed for a detailed description of low Mr subunits of glutenin in different cultivars following a genetic approach based on the correspondence between the alleles at the Gli-1 and Glu-3 loci.

The Biochemistry and Molecular Biology of Seed Storage Proteins

Most plants synthesise proteins in their organs of reproduction and propagation, such as seeds of gymnosperms and angiosperms. Storage proteins are usually located in two tissues. In dicotyledonous plants they may be located in the diploid cotyledons (exalbuminous), in the triploid endosperm (albuminous) or, occasionally, in both tissues. In monocotyledonous cereals they are primarily located in the triploid endosperm tissue. They are deposited in high amounts in the seed, in discrete deposits (protein bodies) and survive desiccation for long periods of time. In most cases, storage proteins lack any other biological activity and simply provide a source of nitrogen, sulphur and carbon skeletons for the developing seedling (Shotwell and Larkins 1989; Shewry 1995).

Recent perspectives on the genetics, biochemistry and functionality of wheat proteins

Abstract Wheat protein is unique among cereal and other plant proteins in its ability to form a dough with viscoelastic properties ideally suited to make bread, biscuit or pasta products. Despite many years of study, we do not have a detailed understanding at the molecular level of the basis for the unique properties of doughs or the ways in which the various constituents contribute to the functional properties of different wheat flours. This paper reviews some recent aspects of the genetics, biochemistry and functionality of wheat proteins, based on new concepts or analytical approaches, that are relevant to the processing qualities of wheat and that provide the potential to make a significant step forward in both our understanding of protein properties and the development of better wheat varieties for the future.

Confocal Raman microscopic characterization of the molecular species responsible for the grain cohesion of Triticum aestivum wheat: effect of chemical treatment

Raman microspectroscopy is a very well appropriate technique for the characterization of the molecules responsible of the wheat grain cohesion, since it is non-destructive and can be readily applied in-situ. The cohesion of the kernel or starchy endosperm depends on a protein content located at the interstices of starch granules. The separation between the kernel and the envelope depends on the composition of the aleurone cells layer, in phenolic acids and pentosans. Confocal Raman microscopy has been performed on kernel sections of various Triticum aestivum samples. Raman spectra recorded at different parts of such sections are very specific, such as spectra of the starchy endosperm protein. The technique has been also used to study the effect of chemical treatment on the binding of the constituents of the aleurone cells walls. In addition, certain marker bands of starch and proteins have been used to construct spectral images.