Search

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'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'un site AG de reconnaissance de la jonction intron-exon. Quatre types d'ADNc issus d'un epissage errone ont ensuite ete detectees lors de l'amplification d'ADNc pour TaSSIIa-D. Parmi celles-ci, neuf ADNc de type II avec une deletion de 16 pb au sein de l'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'extremite de l'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'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 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 [...]

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'il serait possible d'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'excellent système racinaire du blé tibétain, les auteurs ont réalisé une analyse QTL pour des caractères racinaires au sein d'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'avérer utiles dans le cadre de programmes d'amélioration génétique. [Traduit par la Rédaction] Mots-clés : blé tibétain semi-sauvage, lignée recombinante fixée, caractère racinaire, locus de caractère quantitatif, corrélation., 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 [...]

Abstract: Gene loss during the formation of hexaploid bread wheat has been repeatedly reported. However, our knowledge on genome-wide analysis of the genes present on a single subgenome (SSG) in [...]

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 [...]

Chromosome translocation is an important driving force in shaping genomes during evolution. Detailed knowledge of chromosome translocations in a given species and its close relatives should increase the efficiency and precision of chromosome engineering in crop improvement. To identify genes flanking the breakpoints of translocations and inversions as a step toward identifying breakpoints in bread wheat, we systematically analysed genes in the Brachypodium genome against wheat survey sequences and bin-mapped ESTs (expressed sequence tags) derived from the hexaploid wheat genotype 'Chinese Spring'. In addition to those well-known translocations between group 4, 5, and 7 chromosomes, this analysis identified genes flanking the three pericentric inversions on chromosomes 2B, 4B, and 5A. However, numerous chromosomal rearrangements reported in early studies could not be confirmed. The genes flanking the breakpoints reported in this study are valuable for isolating these breakpoints. Key words: genome evolution, bread wheat, inversion, translocation breakpoint, Brachypodium. La translocation chromosomique est l'un des moteurs de l'evolution des genomes. Une connaissance approfondie des translocations chromosomiques au sein d'une espece et ses proches parents pourrait augmenter l'efficience et la precision de l'ingenierie chromosomique en amelioration varietale. Afin d'identifier les genes bordant les jonctions de translocations et d'inversions, en vue d'identifier ces jonctions chez le ble tendre, les auteurs ont systematiquement compare les genes du genome de Brachypodium avec les sequences de survol et les EST (expressed sequence tags) assignes a la carte genetique chez le ble pour le genotype hexpaploide 'Chinese Spring'. En plus des translocations bien connues entre les chromosomes des groupes 4, 5 et 7, cette analyse a permis d'identifier des genes bordant trois inversions pericentriques sur les chromosomes 2B, 4B et 5A. Cependant, de nombreux rearrangements chromosomiques rapportes dans des etudes anterieures n'ont pas ete confirmes. Les genes bordant les jonctions rapportees dans ce travail seront utiles pour isoler ces jonctions. [Traduit par la Redaction] Mots-cles : evolution du genome, ble tendre, inversion, jonction de translocation, Brachypodium., Introduction It is widely believed that chromosome translocation is an important driving force in shaping genomes during evolution (Brown and O'Neill 2010; Burt et al. 1999; Colson et al. 2004; [...]

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.