Molecular characterization of α-gliadin genes from common wheat cultivar Zhengmai 004 and their role in quality and celiac disease

A total of 43 unique clones(Z4A-1 to Z4A-43 with GenBank accession numbers of HM120221, HM120222, JX828270, JN831402 to JN831406, and KC715889 to KC715923, respectively) were amplified and cloned from common wheat cultivar Zhengmai 004 using a PCR-based strategy. They included 22 full-ORF α-gliadin genes and 21 pseudogenes containing at least one in-frame stop codon. Comparative analysis of the deduced amino acid sequences showed that all the isolated genes displayed the typical structural features of α-gliadin genes and that the putative proteins of Z4A-7, Z4A-14, Z4A-17 and Z4A-20 had an extra cysteine residue in the unique domain II, while Z4A-15 lacked the second conserved cysteine residue in the unique domain I. The two fusion proteins of Z4A-15 and Z4A-20 were successfully detected by SDS-PAGE and Western blotting, although the protein level was relatively low. Based on the occurrence of the four major epitopes, as well as the lengths of the two glutamine repeats, 8, 6, and 8 genes were assigned to the Gli-2 loci on the respective chromosomes 6A, 6B, and 6D and a total of respectively 16, 0 and 23 immunogenic peptides were identified. In addition, 4 of the 5 genes with odd numbers of cysteine residues were assigned to chromosome 6D, suggesting that common wheat cultivar Zhengmai 004 has the potential to induce celiac disease(CD) and that the D genome exerts the most influence on gluten quality, but is the most deleterious for CD patients. By phylogenetic analysis, 11 exceptional α-gliadins with few or no immunogenic peptides from Triticum monococcum and Aegilops tauschii were detected, a finding that further supports the prospect of CD prevention. Finally, secondary structure prediction showed that most(98.48%) of the α-gliadins invariably contained five conserved α-helices(H1 to H5) in the two glutamine repeats and unique domains and 67.68% of the α-gliadins also contained a β-strand(S) in the C-terminal unique domains. An absent α-helix H2, 1–2 extra α-helices, or an additional β-strand(SE) also probably occurred in some cases. Of the 22 cloned genes in this work, 10 putative proteins contained 1–2 extra α-helices in addition to the five conserved α-helices or the additional β-strand. The observation that most of the α-helices and β-strands were present in the two unique domains and that an extra α-helix also probably occurred in the two glutamine repeats in some desirable genes strongly suggested that these two uniquedomains are the most important regions for the function of α-gliadins, although the glutamine repeats would also contribute in some cases.

Performance evaluation of multiple relays cooperative GBn-ARQ with limited retransmission

We investigate the performance of multiple relays cooperative go back n automatic repeat request(MRC-GBn-ARQ) protocol with limited retransmission. An N +2-state Markov transition model is constructed for analyzing arbitrary packet transmission process with limited retransmission. Then the system's steadystate distribution is derived by using the Kolmogorov equations.Further, the mean packet transmission delay and startup delay are obtained respectively; the channel utilization is derived based on discrete-time Geom/G/1 queue model with startup. Also, we get the energy efficiency of the MRC-GBn-ARQ based on energy analytical model. Especially, the presented models are contrary to the classical ARQ protocols of always allowing infinite retransmission, and our analysis of the MRC-GBn-ARQ protocol with limited retransmission provides theoretical results for reducing the system's delay and energy consumption. Finally, analysis is validated through some numerical simulations.

Introgression of QTL from Aegilops tauschii enhances yield-related traits in common wheat

To break the narrow diversity bottleneck of the wheat D genome, a set of Aegilops tauschii-wheat introgression(A-WI) lines was developed by crossing Ae. tauschii accession T015 with common wheat elite cultivar Zhoumai 18(Zhou18). A high-density genetic map was constructed based on Single Nucleotide Polymorphism(SNP) markers and 15 yield-related traits were evaluated in 11 environments for detecting quantitative trait loci(QTL). A total of 27 environmentally stable QTL were identified in at least five environments, 20 of which were derived from Ae. tauschii T015, explaining up to 24.27% of the phenotypic variations. The major QTL for kernel length(KL), QKl-2D.5, was delimited to a physical interval of approximately 2.6 Mb harboring 52 candidate genes. Three Kompetitive Allele Specific PCR(KASP)markers were successfully developed based on nonsynonymous nucleotide mutations of candidate gene AetT093_2Dv1G100900.1 and showed that A-WI lines with the T015 haplotype had significantly longer KL than the Zhou18 haplotype across all 11 environments. Four primary valuable A-WIs with good trait performance and carrying yield-related QTL were selected for breeding improvement. The results will facilitate the efficient transfer of beneficial genes from Ae. tauschii into wheat cultivars to improve wheat yield and other traits.

New insights into the dispersion history and adaptive evolution of taxon Aegilops tauschii in China

Aegilops tauschii,the wild progenitor of wheat D-genome and a valuable germplasm for wheat improvement,has a wide natural distribution from eastern Turkey to China.However,the phylogenetic relationship and dispersion history of Ae.tauschii in China has not been scientifically clarified.In this study,we genotyped 208 accessions(with 104 in China)using dd RAD sequencing and 55K SNP array,and classified the population into six sublineages.Three possible spreading routes or events were identified,resulting in specific distribution patterns,with four sublineages found in Xinjiang,one in Qinghai,two in Shaanxi and one in Henan.We also established the correlation of SNP-based,karyotypebased and spike-morphology-based techniques to demonstrate the internal classification of Ae.tauschii,and developed consensus dataset with 1245 putative accessions by merging data previously published.Our analysis suggested that eight inter-lineage accessions could be assigned to the putative Lineage 3and these accessions would help to conserve the genetic diversity of the species.By developing the consensus phylogenetic relationships of Ae.tauschii,our work validated the hypothesis on the dispersal history of Ae.tauschii in China,and contributed to the efficient and comprehensive germplasm-mining of the species.