Search

Abstract Background High molecular weight glutenin subunits (HMW-GSs), encoded by the genes at Glu-1 loci in wheat and its related species, are significant in the determination of grain processing quality. However, the diversity and variations of HMW-GSs are relatively low in bread wheat. More interests are now focused on wheat wild relatives in Triticeae. The genus Aegilops represents an important germplasm for novel HWM-GSs and other useful genes for wheat genetic improvement. Results Six novel Glu-1 alleles and HMW-GSs were identified and characterized from three species of Aegilops section Sitopsis (S genome). Both open reading frames (ORFs) and promoter regions of these Glu-1 alleles were sequenced and characterized. The ORFs of Sitopsis Glu-1 genes are approximately 2.9 kb and 2.3 kb for x-type and y-type subunits, respectively. Although the primary structures of Sitopsis HMW-GSs are similar to those of previously reported ones, all six x-type or y-type subunits have the large fragment insertions. Our comparative analyses of the deduced amino acid sequences verified that Aegilops section Sitopsis species encode novel HMW-GSs with their molecular weights larger than almost all other known HMW-GSs. The Glu-1 promoter sequences share the high homology among S genome. Our phylogenetic analyses by both network and NJ tree indicated that there is a close phylogenetic evolutionary relationship of x-type and y-type subunit between S and D genome. Conclusions The large molecular weight of HMW-GSs from S genome is a unique feature identified in this study. Such large subunits are resulted from the duplications of repetitive domains in Sitopsis HMW-GSs. The unequal crossover events are the most likely mechanism of variations in glutenin subunits. The S genome-encoded subunits, 1Dx2.2 and 1Dx2.2* have independent origins, although they share similar evolutionary mechanism. As HMW-GSs play a key role in wheat baking quality, these large Sitopsis glutenin subunits can be used as special genetic resources for wheat quality improvement.

Abstract Background Various enzyme inhibitors act on key insect gut digestive hydrolases, including alpha-amylases and proteinases. Alpha-amylase inhibitors have been widely investigated for their possible use in strengthening a plant's defense against insects that are highly dependent on starch as an energy source. We attempted to unravel the diversity of monomeric alpha-amylase inhibitor genes of Israeli and Golan Heights' wild emmer wheat with different ecological factors (e.g., geography, water, and temperature). Population methods that analyze the nature and frequency of allele diversity within a species and the codon analysis method (comparing patterns of synonymous and non-synonymous changes in protein coding sequences) were used to detect natural selection. Results Three hundred and forty-eight sequences encoding monomeric alpha-amylase inhibitors (WMAI) were obtained from 14 populations of wild emmer wheat. The frequency of SNPs in WMAI genes was 1 out of 16.3 bases, where 28 SNPs were detected in the coding sequence. The results of purifying and the positive selection hypothesis (p < 0.05) showed that the sequences of WMAI were contributed by both natural selection and co-evolution, which ensured conservation of protein function and inhibition against diverse insect amylases. The majority of amino acid substitutions occurred at the C-terminal (positive selection domain), which ensured the stability of WMAI. SNPs in this gene could be classified into several categories associated with water, temperature, and geographic factors, respectively. Conclusions Great diversity at the WMAI locus, both between and within populations, was detected in the populations of wild emmer wheat. It was revealed that WMAI were naturally selected for across populations by a ratio of dN/dS as expected. Ecological factors, singly or in combination, explained a significant proportion of the variations in the SNPs. A sharp genetic divergence over very short geographic distances compared to a small genetic divergence between large geographic distances also suggested that the SNPs were subjected to natural selection, and ecological factors had an important evolutionary role in polymorphisms at this locus. According to population and codon analysis, these results suggested that monomeric alpha-amylase inhibitors are adaptively selected under different environmental conditions.

Abstract Background The unique properties of wheat flour primarily depend on gluten, which is the most important source of protein for human being. γ-Gliadins have been considered to be the most ancient of the wheat gluten family. The complex family structure of γ-gliadins complicates the determination of their function. Moreover, γ-gliadins contain several sets of celiac disease epitopes. However, no systematic research has been conducted yet. Results A total of 170 γ-gliadin genes were isolated from common wheat and its closely related species, among which 138 sequences are putatively functional. The ORF lengths of these sequences range from 678 to 1089 bp, and the repetitive region is mainly responsible for the size heterogeneity of γ-gliadins. The repeat motif P(Q/L/S/T/I/V/R/A)F(S/Y/V/Q/I/C/L)P(R/L/S/T/H/C/Y)Q1–2(P(S/L/T/A/F/H)QQ)1–2is repeated from 7 to 22 times. Sequence polymorphism and linkage disequilibrium analyses show that γ-gliadins are highly diverse. Phylogenic analyses indicate that there is no obvious discrimination between Sitopsis and Ae. tauschii at the Gli-1 loci, compared with diploid wheat. According to the number and placement of cysteine residues, we defined nine cysteine patterns and 17 subgroups. Alternatively, we classified γ-gliadins into two types based on the length of repetitive domain. Amino acid composition analyses indicate that there is a wide range of essential amino acids in γ-gliadins, and those γ-gliadins from subgroup SG-10 and SG-12 and γ-gliadins with a short repetitive domain are more nutritional. A screening of toxic epitopes shows that γ-gliadins with a pattern of C9 and γ-gliadins with a short repetitive domain almost lack any epitopes. Conclusion γ-Gliadin sequences in wheat and closely related Aegilops species are diverse. Each group/subgroup contributes differently to nutritional quality and epitope content. It is suggested that the genes with a short repetitive domain are more nutritional and valuable. Therefore, it is possible to breed wheat varieties, the γ-gliadins of which are less, even non-toxic and more nutritional.

Abstract Background High-molecular-weight glutenin subunits (HMW-GSs) have been considered as most important seed storage proteins for wheat flour quality. 1Ay subunits are of great interest because they are always silent in common wheat. The presence of expressed 1Ay subunits in diploid and tetraploid wheat genotypes makes it possible to investigate molecular information of active 1Ay genes. Results We identified 1Ay subunits with different electrophoretic mobility from 141 accessions of diploid and tetraploid wheats, and obtained the complete ORFs and 5' flanking sequences of 1Ay genes including 6 active and 3 inactive ones. Furthermore, the 5' flanking sequences were characterized from 23 wild diploid species of Triticeae. All 6 active 1Ay possess a typical HMW-GS primary structure and some novel characteristics. The conserved cysteine residue within the repetitive domain of y-type subunits was replaced by phenylalanine residue in subunits of 1Ay (Tu-e1), 1Ay (Tu-e2), 1Ay (Ta-e2) and 1Ay (Td-e). Particularly, 1Ay (Ta-e3) has an unusual large molecular weight of 2202 bp and was one of the known largest y-type HMW-GSs. The translations of 1Ay (Tu-s), 1Ay (Ta-s) and 1Ay (Td-s) were disrupted by premature stop codons in their coding regions. The 5' flanking sequences of active and inactive 1Ay genes differ in a few base substitutions and insertions or deletions. The 85 bp deletions have been found in promoter regions of all 1Ay genes and the corresponding positions of 6 species from Aegilops and Hordeum. Conclusion The possession of larger molecular weight and fewer conserved cysteine residues are unique structural features of 1Ay genes; it would be interested to express them in bread wheat and further to examine their impact to processing quality of wheat. The 1Ay genes from T. urartu are closer to the genes from T. turgidum dicoccon and T. aestivum, than those from T. monococcum aegilopoides. The 85 bp deletion and some variations in the 5'flanking region, have not interrupted expression of 1Ay genes, whereas the defects in the coding regions could be responsible to the silence of the 1Ay genes. Some mutational events in more distant distal promoter regions are also possible causes for the inactivation of 1Ay genes.

Abstract Background α-Amylase inhibitors are attractive candidates for the control of seed weevils, as these insects are highly dependent on starch as an energy source. In this study, we aimed to reveal the structure and diversity of dimeric α-amylase inhibitor genes in wild emmer wheat from Israel and to elucidate the relationship between the emmer wheat genes and ecological factors using single nucleotide polymorphism (SNP) markers. Another objective of this study was to find out whether there were any correlations between SNPs in functional protein-coding genes and the environment. Results The influence of ecological factors on the genetic structure of dimeric α-amylase inhibitor genes was evaluated by specific SNP markers. A total of 244 dimeric α-amylase inhibitor genes were obtained from 13 accessions in 10 populations. Seventy-five polymorphic positions and 74 haplotypes were defined by sequence analysis. Sixteen out of the 75 SNP markers were designed to detect SNP variations in wild emmer wheat accessions from different populations in Israel. The proportion of polymorphic loci P (5%), the expected heterozygosity He, and Shannon's information index in the 16 populations were 0.887, 0.404, and 0.589, respectively. The populations of wild emmer wheat showed great diversity in gene loci both between and within populations. Based on the SNP marker data, the genetic distance of pair-wise comparisons of the 16 populations displayed a sharp genetic differentiation over long geographic distances. The values of P, He, and Shannon's information index were negatively correlated with three climatic moisture factors, whereas the same values were positively correlated by Spearman rank correlation coefficients' analysis with some of the other ecological factors. Conclusion The populations of wild emmer wheat showed a wide range of diversity in dimeric α-amylase inhibitors, both between and within populations. We suggested that SNP markers are useful for the estimation of genetic diversity of functional genes in wild emmer wheat. These results show significant correlations between SNPs in the α-amylase inhibitor genes and ecological factors affecting diversity. Ecological factors, singly or in combination, explained a significant proportion of the variations in the SNPs, and the SNPs could be classified into several categories as ecogeographical predictors. It was suggested that the SNPs in the α-amylase inhibitor genes have been subjected to natural selection, and ecological factors had an important evolutionary influence on gene differentiation at specific loci.

ATP‐binding cassette (ABC) transporters hydrolyse ATP to transport various substrates. Previous studies have shown that ABC transporters are responsible for transporting plant hormones and heavy metals, thus contributing to plant immunity. Herein, we identified a wheat G‐type ABC transporter, TaABCG2‐5B, that responds to salicylic acid (SA) treatment and is induced by Fusarium graminearum, the primary pathogen causing Fusarium head blight (FHB). The loss‐of‐function mutation of TaABCG2‐5B (ΔTaabcg2‐5B) reduced SA accumulation and increased susceptibility to F. graminearum. Conversely, overexpression of TaABCG2‐5B (OE‐TaABCG2‐5B) exerted the opposite effect. Quantification of intracellular SA in ΔTaabcg2‐5B and OE‐TaABCG2‐5B protoplasts revealed that TaABCG2‐5B acts as an importer, facilitating the transport of SA into the cytoplasm. This role was further confirmed by Cd2+ absorption experiments in wheat roots, indicating that TaABCG2‐5B also participates in Cd2+ transport. Thus, TaABCG2‐5B acts as an importer and is crucial for transporting multiple substrates. Notably, the homologous gene TaABCG2‐5A also facilitated Cd2+ uptake in wheat roots but did not significantly influence SA accumulation or FHB resistance. Therefore, TaABCG2 could be a valuable target for enhancing wheat tolerance to Cd2+ and improving FHB resistance. [ABSTRACT FROM AUTHOR]

Effective tiller number (ETN) directly affects panicle number and is closely related to wheat grain yield. Mining quantitative trait loci (QTLs) associated with wheat tiller number and analyzing the correlation between tiller number and other important agronomic traits can provide the theoretical basis for molecular breeding. In this study, we first proposed and established a novel genetic analysis framework of "multiple environmental assessments-depth analysis of individual traits-comprehensive evaluation of various traits-friendly marker development-verification in different backgrounds". Using this approach, low-tillering QTLs were identified and validated base on an F6 recombinant inbred line population (MC population) derived from the low-tillering plant msf and Chuannong 16 (CN16), phenotypic data of effective tillers from multiple environments, and a 16K chip-based constructed genetic linkage map. QTL mapping results showed that there were four QTLs controlling tillering on chromosomes 1A, 5A, and 6D, respectively. Qltn.sau-MC-1A was a stable and major low-tillering QTL explaining 13.39%--60.40% of the phenotypic variation rate, and its positive allele was from msf. Phenotypic analysis showed that ETN of the lines carrying the positive allele of Qltn.sau-MC-1A was significantly less than those with the negative alleles. Correlation analysis showed that ETN had a significantly positive correlation with plant height (PH), and a significantly negative correlation with thousand kernel weight (TKW), kernel number per spike (KNPS), kernel weight per spike (KWPS), and flag leaf width (FLW), but no significantly correlation with flag leaf length (FLL) and anthesis date (AD). Genetic analysis showed that positive allele of Qltn.sau-MC-1A had a significant effect on increasing KNPS, KWPS, and TKW, but delaying AD. Validation results in different backgrounds suggested that the ETN of lines carrying positive alleles from Qltn.sau-MC-1A could be significantly decreased. Collectively, we established a new genetic mapping approach and further used it to identify and validate a major QTL controlling low-tiller number, Qltn.sau-MC-1A, which laid a foundation for further fine mapping and understanding the mechanism of tiller formation. [ABSTRACT FROM AUTHOR]

Introduction Starch is a major component (65%-75%) of bread wheat grains. Its composition directly determines wheat yield, and together with its physicochemical properties can affect flour processing quality. Furthermore, starch [...], We evaluated the SGP-1 protein composition of 368 Chinese wheat landraces using SDS-PAGE. The SGP-D1 null type was identified in three accessions (Xiaoqingmang, Pushanbamai, and P119). An 18-bp deletion and 9-bp variation were found at the junction region of the 7th intron and 8th exon, leading to deletion of the intron-exon junction recognition site AG when aligned the 8261-bp DNA sequence of TaSSIIa-D in Pushanbamai with that of Chinese Spring. Four cDNA types with mis-spliced isoforms were subsequently detected through amplification of TaSSIIa-D cDNAs. Among these, nine type II cDNAs with a 16-bp deletion in the 8th exon were detected, indicating that the major transcriptional pattern of TaSSIIa in Pushanbamai is type II. In the type IV cDNA, a 97-bp sequence remains undeleted in the end of the 5th exon. The amylose content in Pushanbamai was significantly higher than that in all control lines under field conditions, which suggested that deletion of SGP-D1 has an efficient impact on amylose content. As the TaSSIIa gene plays an important role in regulating the content of amylose, it is anticipated that these natural variants of TaSSIIa-D will provide useful resources for quality improvement in wheat. Key words: Chinese wheat landrace, starch, amylose, TaSSIIa, alternative splicing. Les auteurs ont evalue la composition en proteine SGP-1 chez 368 varietes de pays chinoises du ble au moyen du SDS-PAGE. Le type nul SGP-D1 a ete identifie chez trois accessions (Xiaoquingmang, Pushanbamai et P119). Lorsque la sequence de 8261 pb de l&apos;allele TaSSIIa-D present chez Pushanbamai a ete comparee a celle de Chinese Spring, une deletion de 18 pb et une variation de 9 pb ont ete observees a la jonction du 7ieme intron et du 8ieme exon, entrainant la deletion d&apos;un site AG de reconnaissance de la jonction intron-exon. Quatre types d&apos;ADNc issus d&apos;un epissage errone ont ensuite ete detectees lors de l&apos;amplification d&apos;ADNc pour TaSSIIa-D. Parmi celles-ci, neuf ADNc de type II avec une deletion de 16 pb au sein de l&apos;exon 8 ont ete detectes, ce qui indique que le principal produit de la transcription de TaSSIIa-D chez Pushanbamai est de type II. Au sein des ADNc de type IV, une sequence de 97 pb est conservee a l&apos;extremite de l&apos;exon 5. Le contenu en amylose chez Pushanbamai est significativement plus eleve que chez toutes les lignees temoins en conditions de champ, ce qui suggere que la deletion de SGP-D1 aurait eu un effet sur la teneur en amylose. Comme le gene TaSSIIa joue un role important dans la regulation de la teneur en amylose, il est anticipe que ces variants naturels de TaSSIIa-D fourniront une ressource utile pour l&apos;amelioration de la qualite chez le ble. [Traduit par la Redaction] Mots-cles : variete de pays chinoise du ble, amidon, amylose, TaSSIIa, epissage alternatif.

Introduction Common wheat (Triticum aestivum L., 2n=6x=42, AABBDD) is one of the most important food crops in the world. With the increase of population, improving the yield of wheat has [...], As a primitive hexaploid wheat resource distributed only in Tibet, Tibetan semi-wild wheat (Triticum aestivum subsp. tibetanum Shao) possesses unique characteristics that could be exploited in wheat breeding programs. Its good root system could offer a stable platform for above-ground components. To detect possible excellent locus for root traits from Tibetan semi-wild wheat, we identified QTLs for root traits using a recombinant inbred line population derived from a cross between Tibetan semi-wild wheat Q1028 and Zhengmai 9023. A total of 15 QTLs on eight chromosomes were detected, including four major QTLs, QMrl.sau-7B, QTrl.sau-4B, QAd.sau-7A, and QSa.sau-4B. The phenotypic variation explained by each of these QTLs ranges from 5.67% to 16.68%. Positive alleles of six QTLs were derived from Q1028. Several novel QTLs for root traits were identified. In addition, significant correlations were detected amongst root traits and agronomic traits. Taken together, these results suggest that Tibetan semi-wild wheat and the newly identified novel QTLs could be useful in future breeding programs. Key words: Tibetan semi-wild wheat, recombinant inbred line, root trait, quantitative trait locus, correlation. Résumé : En tant que ressource génétique primitive pour le blé hexaploïde qui est uniquement présente au Tibet, le blé tibétain semi-sauvage (Triticum aestivum subsp. tibetanum Shao) possède des caractéristiques uniques qu&apos;il serait possible d&apos;exploiter en amélioration génétique du blé. Son bon système racinaire pourrait offrir une plate-forme stable pour les parties aériennes. Afin de détecter des locus contribuant à l&apos;excellent système racinaire du blé tibétain, les auteurs ont réalisé une analyse QTL pour des caractères racinaires au sein d&apos;une collection de lignées recombinantes fixées issue du croisement entre le blé tibétain Q1028 et Zhengmai 9023. Un total de 15 QTL sur huit chromosomes a été détecté, incluant quatre QTL majeurs (QMr1.sau-7B, QTrl.sau-4B, QAd.sau-7A et QSa.sau-4B). La part de la variation phénotypique expliquée par chacun de ces QTL variait entre 5,67 et 16,68 %. Des allèles positifs pour six des QTL étaient dérivés de Q1028. Plusieurs nouveaux QTL pour des caractères racinaires ont été identifiés. De plus, des corrélations significatives ont été détectées entre les caractères racinaires et agronomiques. Ensemble, ces résultats suggèrent que le blé tibétain semi-sauvage et les QTL nouvellement identifiés pourraient s&apos;avérer utiles dans le cadre de programmes d&apos;amélioration génétique. [Traduit par la Rédaction] Mots-clés : blé tibétain semi-sauvage, lignée recombinante fixée, caractère racinaire, locus de caractère quantitatif, corrélation.

ADP-glucose pyrophosphorylase (AGP), which consists of two large subunits (AGP-L) and two small subunits (AGP-S), controls the rate-limiting step in the starch biosynthetic pathway. In this study, a full-length open [...]