Disulphide structure of high-molecular-weight (HMW-) gliadins as affected by terminators

This study aimed at elucidating SS-bonds of HMW-gliadins (HGL) from wheat with the focus on terminators of glutenin polymerisation. HGL from wheat flour extracts non-treated or treated with the S-alkylation reagent N-ethylmaleinimide (NEMI) were compared. HGL from wheat flour Akteur were isolated, hydrolysed with thermolysin and the resulting peptides pre-separated by gel permeation chromatography and analysed by liquid chromatography/mass-spectrometry using alternating electron transfer dissociation/collision-induced dissociation. Altogether, 22 and 28 SS-peptides from samples without and with NEMI treatment, respectively, were identified. Twenty-six peptides included standard SS-bonds of α- and γ-gliadins, high-molecular-weight and low-molecular-weight glutenin subunits. Eleven SS-bonds were identified for the first time. Fifteen peptides unique to HGL contained cysteine residues from gliadins with an odd number of cysteines (ω5-, α- and γ-gliadins). Thus, gliadins with an odd number of cysteines, glutathione and cysteine had acted as terminators of glutenin polymerisation. Decisive differences between samples without and with NEMI treatment were not obvious showing that the termination of polymerisation was already completed in the flour. The two HGL samples, however, were different in the majority of ten peptides that included disulphide-linked low-molecular-weight (LMW) thiols such as glutathione and cysteine with the former being enriched in the non-treated HGL-sample.     

野生大豆（Glycinesoja）HSP的研究──Ⅰ．黄河下游和松花江下游地区野生大豆HSP诱导合成的比较研究

本文对黄河下游地区野生大豆“７５８３”和松花江下游地区野生大豆“０１—３２”的发育胚根（Ｓｅｅｄｌｉｎｇｓ）在４０℃下热击分别为２、４、６、８、１０ｈｒ，比较其热击反应（ＨＳＲ）及其热击蛋白（ＨＳＰ）诱导合成的种类、累积动态。研究结果指出黄河下游地区野生大豆对２ｈｒ热击反应较松花江下游地区野生大豆反应迟钝，热击４ｈｒ前者ＨＳＰ种类倍增，且小分子量ＨＳＰ（ＬＭＷＨＳＰ）显著多于后者。ＨＳＰ累积高峰有别，松花江下游野生大豆早于黄河下游野生大豆４个小时，且ＨＳＰ累积量始终高于后者。研究还发现野生大豆存在干热击蛋白（ＨｅａｔＳｈｏｃｋＣｏｇｎａｔｅＰｒｏｔｅｉｎｓ，ＨＳＣＰ）。     

Effect of allelic variation at the Glu-3/Gli-1 loci on breadmaking quality parameters in hexaploid wheat (Triticum aestivum L.)

Low molecular weight glutenin subunits (LMW-GS) encoded by the Glu-3 loci are known to contribute to wheat breadmaking quality. However, the specific effect of individual Glu-3 alleles is not well understood due to their complex protein banding patterns in SDS-PAGE and tight linkage with gliadins at the Gli-1 locus. Using DNA markers and a backcross program, we developed a set of nine near isogenic lines (NILs) including different Glu-A3/Gli-A1 or Glu-B3/Gli-B1 alleles in the genetic background of the Argentine variety ProINTA Imperial. The nine NILs and the control were evaluated in three different field trials in Argentina. Significant genotype-by-environment interactions were detected for most quality parameters indicating that the effects of the Glu-3/Gli-1 alleles are modulated by environmental differences. None of the NILs showed differences in total flour protein content, but relative changes in the abundance of particular classes of proteins cannot be ruled out. On average, the Glu-A3f, Glu-B3b, Glu-B3g and Glu-B3i_Man alleles were associated with the highest values in gluten strength-related parameters, while Glu-A3e, Glu-B3a and Glu-B3i_Chu were consistently associated with weak gluten and low quality values. The value of different Glu-3/Gli-1 allele combinations to improve breadmaking quality is discussed.     

An assessment of cultivated emmer germplasm for gluten proteins

The storage protein composition of 61 accessions of Triticum dicoccum was analyzed by SDS-PAGE (HMW- and LMW-glutenin subunits) and Acid-PAGE (gliadins). In the HMW-glutenin subunits, four allelic variants at the Glu-A1 and eight at the Glu-B1 locus were detected resulting in a total of 17 patterns. The Glu-B1 locus was found to be more polymorphic than the Glu-A1 locus. Interestingly, the presence of HMW subunits like 13+16, 2^∗ and 1 associated with good quality was observed. Three accessions were null for both the Glu-A1 and Glu-B1 loci. There was less variation for gliadins. Three different gamma gliadin fractions coded by Gli-B1 locus were detected and there were eight different LMW-B glutenin patterns at the Glu-3 loci. The variability can be used to improve the utility of this crop.     

Improving the end use properties of wheat by manipulating the grain protein composition

The wheat storage proteins account for up to about 60% of the totalgrain proteins. They correspond to the gluten proteins, which form avisco-elastic network that enables dough to be processed into bread, pastaand other products. We are using a range of biochemical, biophysical andmolecular approaches to characterize gluten proteins and to understandtheir role in determining the grain processing properties, focusing on thehigh molecular weight (HMW) subunits of glutenin which are majordeterminants of dough strength. We are also using genetic engineering toexplore the mechanism of glutenin elasticity and to effect improvements,by inserting genes encoding mutant and wild type HMW subunits intomodel lines and commercial cultivars.