Gli-1 Loci Research Articles

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

Alkylated glutenin subunits of F 7 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 M r glutenin subunits are encoded. The Glu-A3 locus was found to code for two low M r subunits in Neepawa and three in Costantino. In this latter cultivar, eight low M r 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 M r 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 Effects of HMW and LMW subunits of glutenin and of gliadins on the technological quality of progeny from four crosses between poor breadmaking quality and strong wheat cultivars

Four F4 populations: Florence Aurore x Armada (FA x A), Armada x Florence Aurore (A x FA), Rex x Corin (R x C) and Corin x Rex (C x R) were derived from reciprocal crosses between strong wheat cultivars (FA, R) and poor breadmaking wheats (A, C). Protein content, Zeleny sedimentation, Pelshenke swelling and Chopin Alveograph tests were used to evaluate the quality of the 120 to 180 lines comprising each family. The direction of the cross had no significant effect on protein content. Analysis of gliadin polypeptides by APAGE of HMW subunits of glutenin by SDS—PAGE and of LMW subunits of glutenin by two-step one-dimensional SDS—PAGE enabled an assessment of the allelic diversity of these proteins and analysis of their effects on the quality of the lines in these paired groups. For the Glu-A1, Glu-B1 and Glu-D1 loci, at which the HMW subunits of glutenin are encoded, and for the Glu-A3, Glu-B3 and Glu-D3 loci, at which the LMW subunits of glutenin are encoded, the alleles provided by the high-quality wheats FA and R had a significant favourable effect on both dough strength and tenacity and on the Pelshenke test values. Recombinants between the Gli-B1 and Glu-B3 loci were identified, which appeared to confirm that gliadins do affect quality. Alleles at the Gli-1 locus, studied with the two first families (FA x A and A x FA), had higher additive effects on dough strength, tenacity and swelling than those at the Glu-A3 and Glu-B3 loci.

Restriction fragment analysis of ‘null’ forms at the Gli-1 loci of bread and durum wheats

Wheat accessions lacking some of the ω- and γ-gliadin components encoded by the Gli-1 loci on the short arm of chromosome 1D in bread wheat and chromosome 1A in durum wheat were studied by two-dimensional polyacrylamide gel electrophoresis and restriction fragment analysis. Digested genomic DNAs of 'normal' and 'null' forms were probed with a cDNA clone related to ω-/γ-gliadins and with a genomic clone encoding an LMW subunit of glutenin. The hybridisation patterns with the ω-/γ-gliadin probe were similar to those of cvs 'Chinese Spring' and 'Langdon' used as standards for bread and durum wheats, respectively, but several restriction fragments located on the 1D chromosome of bread wheat and the 1A chromosome of durum wheat were absent in the 'null' forms. In addition, specific LMW glutenin fragments encoded by the same chromosomes were also absent in the 'null' forms, suggesting that simultaneous deletions of blocks of genes for both ω-/γ-gliadins and LMW glutenins had occurred. Comparisons of the protein and RFLP patterns enabled some proteins to be mapped to specific restriction fragments.

Characterization and organization of gene families at the Gli-1 loci of bread and durum wheats by restriction fragment analysis

Probes related to γ-gliadins and to the LMW subunits of glutenin were used to determine the complexity of the Gli-1 loci, by RFLP analysis of euploid and aneuploid lines of bread wheat cv Chinese Spring and durum wheat cv Langdon. The two probes hybridised to separate sets of fragments derived from chromosomes 1 A, 1 B and 1D. The fragments related to the LMW subunit probe had a total copy number in HindIII digests of about 35 in Chinese Spring and 17 in Langdon, with more fragments derived from chromosomes 1D. The fragments hybridising to the γ-gliadin probe could be divided into two classes, based on whether they hybridised to the whole probe at high stringency or to the 3' nonrepetitive region at moderate stringency. The fragments that failed to hybridise under these conditions were considered to be related to ω-gliadins. The fragments related to γ - and co-gliadins had total copy numbers of about 39 and 16, respectively, in HindIII digests of Chinese Spring, and about 24 and 12, respectively, in Langdon.

Gliadin gene location and C-banding identification of Aegilops longissima chromosomes added to wheat

Gliadin protein components from Aegilops longissima were separated by two-dimensional electrophoresis. No equivalents for α-gliadin were noted. Addition and substitution lines of Ae. longissima in Triticum aestivum 'Chinese Spring' allowed the identification of homoeologous Gli-1 and Gli-2 loci in Ae. longissima chromosomes 1S1 and 6S1. The chromosomal constitution of the alien addition lines was ascertained by C-banding. In addition, C-banding analysis revealed that the Ae. longissima addition set was incomplete as only six distinct addition lines were identified. No evidence for structural modifications between the alien chromosomes in the lines and their Ae. longissima counterparts was found.Key words: gliadins, C-banding, gene location, Aegilops longissima, wheat.

Chromosomal location of gliadin coding genes in T. aestivum ssp. spelta and evidence on the lack of components controlled by Gli-2 loci in wheat aneuploids

Electrophoretical analyses of the gliadin fraction extracted from seeds of the intervarietal substitution lines of T. aestivum ssp. spelta in the T. aestivum ssp. vulgare cv 'Chinese Spring' for the homoeologous groups 1 and 6 and substitution lines of 6D chromosome of 'Chinese Spring' in the durum wheat cv 'Langdon' allowed the identification of seeds without gliadin proteins controlled by genes on chromosome 6A and 6B. A gliadin component of 'Chinese Spring', not previously assigned to any specific chromosome, is controlled by chromosome 6D in the 6D (6A) and 6D (6B) disomic substitution lines of 'Langdon'. Additional genes controlling the synthesis of this component may be present on other chromosomes, very likely 6A and 6B, since the analysis of the 'Chinese Spring' compensating nullisomic-tetrasomics involving the 6D chromosome does not show the loss of this component or any apparent change in staining intensity. Chromosomal location data and two-dimensional gliadin maps reveal close homologies between the two hexaploid wheats, 'Chinese Spring' (T. aestivum ssp. vulgare) and T. aestivum ssp. spelta, belonging to different subspecies in the hexaploid group of genomic formula AABBDD. The comparison of gliadin electrophoretic patterns aiding in the identification of evolutionary pathways in wheat is stressed.

Influence of gliadin composition and high molecular weight subunits of glutenin on dough properties in an F 3 population of a bread wheat cross

Dough properties (maximum resistance, extensibility and dough breakdown), flour protein content, the high-molecular-weight (HMW) subunits of glutenin and gliadin composition were determined in an F 3 population of the bread wheat cross ‘Nuri 70’ x ‘UL 82’. Variation in dough properties was not influenced by protein content. HMW subunits of glutenin, particularly those of the Glu-D1 locus were largely responsible for differences in dough breakdown and maximum resistance but not for extensibility of the dough. The Glu-D1d allele (subunits 5 and 10) inherited from ‘Nuri 70’ was associated with lower dough breakdown and higher maximum resistance than its allelic counterpart Glu-D1a (2 and 12) derived from ‘UL 82’ while the subunits 17 and 18 of the Glu-B1 locus conferred slightly greater dough extensibility. No significant association was observed between the dough properties and gliadin composition in the entire population. However, in the sub-population of lines heterozygous at the Glu-D1 locus, the presence of gliadin components homozygous at one of the Gli-1 loci, derived from the ‘UL 82’ parent, resulted in significantly lower mean dough breakdown values than either the heterozygous condition or parental gliadin components from ‘Nuri 70’.

Molecular analysis of γ-gliadin gene families at the complex Gli-1 locus of bread wheat (T. aestivum L.)

A cDNA clone (pTag1436) carrying a complete coding sequence for a γ-gliadin polypeptide has been identified and sequenced. By hybridisation to size fractionated poly A(+) RNA from wheat nullisomic-tetrasomic lines, homologous transcripts from the Gli-A1, Gli-B1 and Gli-D1 loci were identified. These mRNAs differed from those complementary to a low molecular weight (LMW) glutenin cDNA clone. Hybridization of pTag1436 to digested wheat DNA produced a pattern of fragments unrelated to that obtained using a LMW glutenin cDNA probe. These results indicate that the γ-gliadin and LMW glutenin families, although both located at the Gli-1 loci, are distinct by hybridisation.

Chromosomal control of wheat gliadin: analysis by reversed-phase high-performance liquid chromatography

Gliadin proteins of the hexaploid wheat variety 'Chinese Spring', and of its nullisomic-tetrasomic and ditelocentric aneuploid lines, were analyzed by reversed-phase high-performance liquid chromatography (RP-HPLC). Reversed-phase separations were carried out at 70°C on C8 and C18 columns using a gradient of increasing acetonitrile concentration in the presence of 0.1% trifluoroacetic acid. Thirty-five components were separated and all were found to be controlled by genes on the short arms of group 1 and group 6 chromosomes (the complex Gli-1 and Gli-2 loci). Results indicated that gluten polypeptides elute as groups in order of increasing hydrophobicity in the following approximate order: (1) albumins plus globulins, (2) ω-gliadins, (3) high molecular weight (MW) glutenin subunits, (4) α-type gliadins, (5) low MW glutenin subunits, and (6) γ-gliadins. The three distinct protein types coded by genes at the complex Gli-I loci (ω-gliadins, γ-gliadins, and low MW glutenin subunits) thus have uniquely different surface hydrophobicities. Similarly, gene locations for hexaploid 'Cheyenne' gliadins and durum gliadin proteins in the varieties 'Langdon', 'Edmore', and 'Kharkovskaya-5' were determined through RP-HPLC analysis of aneuploid lines. All results confirm known locations of genes for gliadin proteins, and demonstrate that RP-HPLC is a powerful new tool for analysis of gliadins in breeding and genetic studies.

Cross-pollination in wheat Triticum aestivum L. and its wild relative Aegilops biuncialis Vis.

Aim. The aim of the study was analysis of outcrossing indices in Triticum aestivum L. plants depending on growth conditions and in natural populations of its wild relative Aegilops biuncialis Vis. using storage proteins as genetic markers. Methods. SDS and APAG electrophoresis was used to identify genotypes at the Glu-1 and Gli-1 loci for single seeds from F2 plants of T. aestivum and in samples from natural populations of Ae. biuncialis. Results. In T. aestivum, significant differences in the frequency of cross-pollination were revealed, from 0.3 to 11 % depending on year’s conditions and the dose of the 1BL/1RS translocation. The high outcrossing rate was observed under low humidity and the absence of precipitations. The frequency of cross-pollination is, on average, 2.3 % in T. aestivum and 4.38 % in Ae. biuncialis. Conclusions. Differences in outcrossing indices between genotypes with different doses of 1BL/1RS are realized only in certain conditions: drought at moderate temperatures favors cross-pollination. The rate of outcrossing is similar in T. aestivum and Ae. biuncialis.Keywords: cross-pollination, Triticum aestivum L., Aegilops biuncialis Vis, storage proteins.