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Genotypes at the storage protein loci Glu-A1, Glu-B1, Glu-D1, Gli-A1, Gli-B1, Gli-D1, Gli-A3 were identified in a group of Greek spring common wheat varieties. These varieties served as the parental forms for producing dihaploid lines. Heterogeneous varieties were revealed.
Pollens of 94G15 and 94G45, two wheat lines added to chromosome Lr.14 and Lr.2 of Leymus racemosus respectively were irradiated via 60Co-gamma rays and then used to hybridize with two common wheat varieties--Yangmai 5 and Mianyang 11. The five plants showing chromosome pairing between T. aestivum and L. racemosus at PMC MI stage were selected from seventeen examined plants of M1 progeny as the result of meiosis configuration analysis of chromosomes treated with Giemsa C-banding and fluorescent in situ hybridization. Among which, two T. aestivum-L. racemosus alien translocation lines--LW8(3)1 and LW11(3)1 were developed on the basis of further identification of M2 RTC chromosomes by C-banding and in situ hybridization. In addition, feasibility and effectiveness of the pollen irradiation in the development of T. aestivum-relatives alien translocations and the availability of the translocation lines of T. aestivum-L. racemosus are also discussed.
Phytochromes are a family of red/far-red light perceiving photoreceptors. The monocot phytochrome family is represented by three members, PHYA, PHYB and PHYC. We have isolated and characterized the first PHY gene member (TaPHYC) from common wheat, Triticum aestivum var. CPAN1676. It codes for a species of the photoreceptor, phyC, which is known to be light-stable in all plants analyzed so far. A sequence of 7.2 kb has been determined, which includes 3.42 kb of coding region. This is the second full-length PHYC gene sequenced from a monocot (first was from rice). TaPHYC gene shares structural similarities with the rice PHYC containing four exons and three introns in the coding region. The 5' UTR is 1.0-kb-long and harbors an upstream open reading frame (URF) encoding 28 aa. Southern blot analysis of TaPHYC indicates that it represents single locus in the wheat genome, although the possibility of additional loci cannot be completely ruled out. Chromosomal localization using nullisomic-tetrasomic lines of Triticum aestivum var. Chinese Spring places TaPHYC on chromosome 4B. PHYC represents a constitutively expressed gene in all the organs tested and under light/dark conditions. However, PHYC was found to be developmentally regulated showing maximal expression in 3-day-old dark-grown seedlings, which declined thereafter. In silico analysis has also been done to compare TaPHYC gene with the partial sequences known from other wheat species and cultivars. The presence of a topoisomerase gene immediately downstream of the PHYC gene, both in rice and wheat genomes, presents yet another example of synteny in cereals and its possible significance has been discussed.
The genetic similarity between 150 accessions, representing 14 diploidand polyploid species of the Triticeae tribe, was investigated following the UPGMA clustering method. Seventy-three common wheat EST-derived SSR markers (EST-SSRs) that were demonstrated to be transferable across several wheat-related species were used. When diploid species only are concerned, all the accessions bearing the same genome were clustered together without ambiguity while the separation between the different sub-species of tetraploid as well as hexaploid wheats was less clear. Dendrograms reconstructed based on data of 16 EST-SSRs mapped on the A genome confirmed that Triticum aestivum and Triticum durum had closer relationships with Triticum urartu than with Triticum monococcum and Triticum boeoticum, supporting the evidence that T. urartu is the A-genome ancestor of polyploid wheats. Similarly, another tree reconstructed based on data of ten EST-SSRs mapped on the B genome showed that Aegilops speltoides had the closest relationship with T. aestivum and T. durum, suggesting that it was the main contributor of the B genome of polyploid wheats. All these results were expected and demonstrate thus that EST-SSR markers are powerful enough for phylogenetic analysis among the Triticeae tribe.
Male sterility of wheat-breeding line 337S (Triticum aestivum L.) is sensitive to both short day-length/low temperature and long day-length/high temperature. 337S was crossed with the common wheat variety, Huamai No. 8 and the F1 was highly fertile. The F2 population segregated in a 15:1 ratio for fertility/sterility in 243 individuals under long day-length/high-temperature. The two thermophotoperiod-responsive male sterile genes were mapped to chromosomes 5B and 2B using Simple Sequence Repeat (SSR) markers and bulked segregant analysis. Partial linkage maps around the sterility loci of chromosomes 2B and 5B were constructed using the 243 individuals in the F2 population. One gene (wptms1) for male sterility was flanked by the SSR markers Xgwm335 and Xgwm371 at a genetic distance in chromosome 5B of 4.1 and 24.4 cM, respectively. The second gene (wptms2) was mapped between markers Xgwm374 and Xgwm120 at a genetic distance of 6.6 and 20.9 cM, respectively. The closest linked markers Xgwm335 (wptms1) and Xgwm374 (wptms2) explained 53 and 38% of phenotypic variation for the fertility. The SSR markers provide a useful tool to transfer the male sterile genes into elite wheat germplasm.
The barley chromosome in wheat was identified by genomic in situ hybridization (GISH) in which biotin labelled total genomic DNA of barley Betzes was used as probe and the unlabelled total DNA of common wheat Chinese Spring (CS) as blocking DNA. A series of wheat materials were tested as follows: two disomic alien substitution and monosomic alien addition lines, 2n = 43; two monosomic alien substitution lines, 2n = 42; seven disomic alien substitution lines, 2n = 42. RFLP probe psr131 on the short arm of the homologous group 2 was used to analyze the barley chromosome in wheat. The result indicated that there was a same band in barley Betzes and substitution line A5. The chromosome 2A of A5 was substituted by the chromosome 2H of barley. These materials will be useful in transferring the valuable genes in the chromosome 2H to wheat.
Intraspecific divergence of hexaploid wheat Triticum spelta was studied by chromosome C-banding in 41 accessions of different geographic origins. The spelt accessions did not differ in karyotype structure or heterochromatin distribution from common wheat, but showed greater intraspecific polymorphism for chromosome rearrangements (translocations, inversions) and banding patterns. On evidence of C-banding patterns, spelt was assumed to occupy an intermediate position between tetraploid and hexaploid wheat species. Accessions of the Asian spelt subspecies had more diverse banding patterns than European accessions. A relatively high frequency of chromosome rearrangements was observed in Iranian accessions. Visual analysis revealed high uniformity of chromosome banding patterns in T. spelta populations of Afghanistan, Spain, and Germany (Bavarian group), suggesting a significant role of the founder effect in their evolution.
Endo-β-1,4-mannanases (MANs) are glycoside hydrolase family 5 (GH5) enzymes that degrade cell wall mannan polysaccharides and participate in plant growth and stress adaptation. This gene family has not been systematically characterized in common wheat (Triticum aestivum L.). Here, we identified 24 TaMAN genes (TaMAN1-TaMAN24) genome-wide and analyzed their phylogeny, gene structures, chromosomal distribution, synteny, and promoter cis-acting elements. Expression profiles under biotic and abiotic stresses were investigated using public databases, salt-stress RNA-seq, and RT-qPCR. TaMAN proteins (386-475 aa) were mainly predicted to localize in the extracellular space. Phylogenetic analysis divided them into three groups, with Groups II and III representing monocot-specific expansions. Family expansion was driven primarily by whole-genome duplication, supplemented by tandem duplication on homoeologous group 6. Promoters were enriched in hormone- and stress-responsive cis-acting elements (ABRE, as-1/CGTCA-motif, W box). TaMAN1, TaMAN5, TaMAN8, TaMAN9, TaMAN16 and TaMAN19 were significantly induced by powdery mildew, while TaMAN3, TaMAN4 and TaMAN19-TaMAN22 rapidly responded to salt stress. This study provides candidate genes for disease-resistant and salt-tolerant wheat breeding.
Food allergies affect 6 to 8% of children and 2% of adults in the United States. For reasons that are not clear, eight types of food account for a vast majority (approximately 90%) of food-induced hypersensitivity reactions. In this study, C57Bl/6 mice were used to test the hypothesis that commonly allergenic foods are intrinsically more immunogenic than rarely allergenic or nonallergenic foods in allergy-susceptible hosts. Groups of mice (n = 4 to 5) were injected intraperitoneally with the protein extracts (plus alum as an adjuvant) from chicken eggs, peanuts, almonds, filberts-hazelnuts, walnuts, soybeans, and wheat (commonly allergenic foods) and coffee, sweet potatoes, carrots, white potatoes, cherries, lettuce, and spinach (rarely allergenic and nonallergenic foods). Primary and secondary immune responses (as measured by specific IgG1 antibody serum levels) were measured by an enzyme-linked immunosorbent assay. Proteins from peanuts, almonds, filberts, sweet potatoes, cherries, and spinach elicited robust primary and/or secondary immune responses. Proteins from eggs, walnuts, and lettuce elicited poor primary responses but significant secondary responses. In contrast, wheat, soybeans, coffee, carrots, and white potatoes elicited barely detectable to poor primary and secondary immune responses. The order of the immunogenicity levels of these foods in mice is as follows: almonds = filberts > spinach (Rubisco) > peanuts > or = sweet potatoes > cherries > lettuce > walnuts > chicken eggs > carrots > or = white potatoes > wheat = coffee = soybeans. In summary, these data demonstrate for the first time that: (i) foods vary widely with regard to their relative immunogenicity in allergy-susceptible hosts and (ii) intrinsic immunogenicity in mice does not distinguish commonly allergenic foods from rarely allergenic or nonallergenic foods.
The individuals of diploid wheat Triticum boeoticum, T. monococcum and T. sinskajae and goatgrass Aegilops squarrosa were picked out with screening the dense spike characteristics. The dense-spike accessions were discovered in diploid wheat (T. sinskajae) and Ae. squarrosa. Inheritance of the dense spike was studied. The trait was found to be controlled by a recessive gene in T. sinskajae and by an incomplete dominant gene in Ae. squarrosa. The dosage effect of dominant gene C was detected in interspecific pentaploid F1 hybrid plants T. compactum x T. palmovae (2n =35, A(u)A(b)BDD genome). The spike of pentaploid hybrid was not so dense as compared to hexaploid wheat T. compactum. This is the first report showing similarity of the expression of dominant gene C on D genome of the hexaploid wheat to that of dense spike gene in Ae. squarrosa. The existence of dense-spike accessions of Ae. squarrosa allows us to hypothesize that the origin of T. compactum is independent from that of common wheat.
BACKGROUND: Centromeres are crucial for precise chromosome segregation and maintaining genome stability during cell division. However, their evolutionary dynamics, particularly in polyploid organisms with complex genomic architectures, remain largely enigmatic. Allopolyploid wheat, with its well-defined hierarchical ploidy series and recent polyploidization history, serves as an excellent model to explore centromere evolution. RESULTS: In this study, we perform a systematic comparative analysis of centromeres in common wheat and its corresponding ancestral species, utilizing the latest comprehensive reference genome assembly available. Our findings reveal that wheat centromeres predominantly consist of five types of centromeric-specific retrotransposon elements (CRWs), with CRW1 and CRW2 being the most prevalent. We identify distinct evolutionary trajectories in the functional centromeres of each subgenome, characterized by variations in copy number, insertion age, and CRW composition. By utilizing CENH3-ChIP data across various ploidy levels, we uncover a series of CRW invasion events that have shaped the evolution of AA subgenome centromeres. Conversely, the evolutionary process of the DD subgenome centromeres involves their expansion from diploid to hexaploid wheat, facilitating adaptation to a larger genomic context. Integration of complete einkorn centromere assemblies and Aegilops tauschii pan-genomes further revealed subgenome-specific centromere evolutionary trajectories. By inclusion of synthetic hexaploid from S2-S3 generations, alongside 2x/6 × natural accessions, we demonstrate that DD subgenome centromere expansion represents a gradual evolutionary process rather than an immediate response to polyploidization. CONCLUSIONS: Our study provides a comprehensive landscape of centromere adaptation, evolution, and maturation, along with insights into how retrotransposon invasions drive centromere evolution in polyploid wheat.
Powdery mildew caused by Erysiphe graminis f. sp. tritici is one of the most important wheat diseases in many regions of the world. Breeding for resistant cultivars has been proved to be an effective and environmentally safe method to control diseases in wheat production. It is necessary to search for more resistance genes for the diversification of resistance genes in wheat breeding. An Isreali wild emmer wheat (Triticum dicoccoides) accession "G-305-M" was found resistant to the prevailing E. graminis f. sp. tritici isolate Race No. 15 in Beijing region. The powdery mildew resistance has been transferred from G-305-M into common wheat by crossing and backcrossing (G-305-M/781//Jing 411* 3). Genetic analysis showed that the resistance was controlled by a single dominant gene at the seedling stage. A segregating BC2F3 family of the cross "G-305-M/781//Jing 411* 3" with 167 plants was chosen for SSR analysis. Totally 96 wheat microsatellite primer pairs were screened, only one primer pair WMS570 could generate polymorphic DNA fragments between the resistant and susceptible plants. After evaluating this polymorphic marker in the segregating population, the microsatellite locus Xgwm570 mapped on chromosome 6AL was found to be linked to the resistance gene, with the estimated genetic distance of 14.9 +/- 3.0 cM. Based on the origin and chromosomal location of the gene, it is suggested that the resistance gene derived from G-305-M should be a novel Pm gene and is temporarily designated MlG.
Information on the contamination of Danish cereals and cereal products with Fusarium toxins is limited and the last survey is from 1984/1985. In the present study, the occurrence of deoxynivalenol (DON), nivalenol (NIV), HT-2 toxin, T-2 toxin and zearalenone (ZON) was investigated in flour of common wheat, durum wheat and rye. The samples were collected from 1998 to 2001 from both mills and the retail market in Denmark. A total of 190 flour samples were analysed for DON and NIV and about 60 samples for HT-2, T-2 toxin and ZON. DON was most frequently detected with an incidence rate of 78% over all samples for all years. The contamination level varied considerably from year to year, and for wheat and rye the highest incidence and DON concentrations were found in samples from the 1998 harvest. There were regular and heavy rainfalls in Denmark during the flowering period of the crops that year, and DON was found in all samples, with mean concentrations in wheat and rye flour of 191 microg kg(-1) (n=14) and 99 microg kg(-1) (n=16), respectively. Comparison of data from each harvest year showed higher contents of DON in samples of wheat (range 20-527 microg kg(-1)) than in rye (20-257 microg kg(-1)). Contents of NIV, HT-2 toxin and ZON in samples of wheat and rye were generally low, and even in positive samples the contents were close to the detection limit of the methods. The T-2 toxin was detected in only a few of the wheat samples and in low amounts. However, the toxin was found in about 50% of the rye samples collected during 1998-2000, with a mean content of 49 microg kg(-1) (n=25). Durum wheat flour showed the highest DON contamination level, and all samples (n=33) collected during 2000 and 2001 contained DON with means and medians above 1100 microg kg(-1). Over 70% of the samples contained more than 500 microg kg(-1) DON, and the highest observed concentration was 2591 microg kg(-1). The concentration of T-2 toxin in durum wheat flour was also high with five of the 10 analysed samples containing more than 100 g kg(-1).
Triticum aestivum (2n = 6x = 42, AABBDD) with Triticum longissimum (2n = 2x = 14; S1S1) cytoplasm ((lo) cytoplasm) has normal fertility and plant vigor. However, the nucleus of durum wheat (Triticum turgidum (2n = 4x = 28, AABB)) is incompatible with the T. longissimum cytoplasm, producing non-viable progeny. This incompatibility is alleviated by scs(ae), a species cytoplasm-specific (scs) gene, on the long arm of chromosome 1D (1DL) of common wheat. The hemizygous (lo) durum scs(ae) line is male sterile and is maintained by crossing to normal durum wheat. After pollination, the seeds produced are either plump and viable (with scs(ae)) or shriveled and inviable (without scsae). Thus, the chromosome with scs(ae) is inherited as a whole without recombination. The objectives of this study were to characterize the chromosome carrying scs(ae) and to determine the process through which this gene was introgressed into the (lo) durum background. Molecular marker analysis with 27 probes and primers mapped to homoeologous group 1 and genomic in situ hybridization using differentially labeled total genomic DNA of durum wheat and Aegilops tauschii suggest the presence of a 1AL segment in place of the distal region of 1DL. Owing to the absence of any detectable duplications or deletions, homoeologous recombination is the most likely mechanism by which this introgression occurred.
New wheat introgression lines were obtained which contain different segments of individual chromosomes of Aegilops tauschii in the Triticum aestivum cv. 'Chinese Spring' background. The introgression lines were developed to examine various subsets of alleles from the wild grass in the genetic background of common wheat. As starting point substitution lines of 'Chinese Spring' in which single chromosomes of the D genome had been replaced by homologous chromosomes of a synthetic wheat were used. Synthetic wheat had been obtained earlier from a cross between the tetraploid emmer (genomes AABB) and wild grass Aegilops tauschii (genome DD). The seven wheat chromosome substitution lines carrying different chromosomes of Ae. tauschii were crossed twice to T. aestivum cv. 'Chinese Spring' and 259 BC1-progeny plants were analysed. Phenotypic evaluation was carried out for different traits such as plant height, spikelet number, peduncle length, flowering time, spike length, tiller number, grain weight per ear, fertility and thousand kernel weight. Genotypic analysis was performed using a set of 65 microsatellite markers previously mapped on the chromosomes of the D genome of wheat. During this analysis recombinant lines carrying different segments of Ae. tauschii chromosomes were detected. Plants containing small introgressions of the alien genetic material were selfed to get homozygous lines and plants carrying large pieces of the donor chromosome were backcrossed again to get smaller introgressions. Further microsatellite analysis of selected BC1F2-progeny plants resulted in detection of a first set of 36 homozygous lines carrying different pieces of Ae. tauschii genome.
From a wild diploid species that is a relative of wheat, Aegilops speltoides, a 301-bp repeat containing 16 copies of a CAA microsatellite was isolated. Southern blot and fluorescence in situ hybridization revealed that approximately 250 bp of the sequence is tandemly arrayed at the centromere regions of A- and B-genome chromosomes of common wheat and rye chromosomes. Although the DNA sequence of this 250-bp repeat showed no notable homology in the databases, the flanking or intervening sequences between the repeats showed high homologies (>82%) to two separate sequences of the gag gene and its upstream region in cereba, a Ty3/gypsy-like retroelement of Hordeum vulgare. Since the amino acid sequence deduced from the 250 bp with seven CAAs showed some similarity ( approximately 53%) to that of the gag gene, we concluded that the 250-bp repeats had also originated from the cereba-like retroelements in diploid wheat such as Ae. speltoides and had formed tandem arrays, whereas the 300-bp repeats were dispersed as a part of cereba-like retroelements. This suggests that some tandem repeats localized at the centromeric regions of cereals and other plant species originated from parts of retrotransposons.
Heterosis was defined as the advantage of hybrid performance over its parents in terms of growth and productivity. Previous studies showed that differential gene expression between hybrids and their parents is responsible for the heterosis; however, information on systematic identification and characterization of the differentially expressed genes are limited. In this study, an interspecific hybrid between common wheat (Triticum aestivum. L., 2n = 6x = 42, AABBDD) line 3338 and spelt (Triticum spelta L. 2n = 6x = 42, AABBDD) line 2463 was found to be highly heterotic in both aerial growth and root related traits, and was then used for expression assay. A modified suppression subtractive hybridization (SSH) was used to generate four subtracted cDNA libraries, and 748 nonreduandant cDNAs were obtained, among which 465 had high sequence similarity to the GenBank entries and represent diverse of functional categories, such as metabolism, cell growth and maintenance, signal transduction, photosynthesis, response to stress, transcription regulation and others. The expression patterns of 68.2% SSH-derived cDNAs were confirmed by reverse Northern blot, and semi-quantitative RT-PCR exhibited the similar results (72.2%). And it was concluded that the genes differentially expressed between hybrids and their parents involved in diverse physiological process pathway, which might be responsible for the observed heterosis.
The polyploid nature of wheat is a key characteristic of the plant. Full-length complementary DNAs (cDNAs) provide essential information that can be used to annotate the genes and provide a functional analysis of these genes and their products. We constructed a full-length cDNA library derived from young spikelets of common wheat, and obtained 24056 expressed sequence tags (ESTs) from both ends of the cDNA clones. These ESTs were grouped into 3605 contigs using the phrap method, representing expressed loci from each of the three genomes. Using BLAST, 3605 contigs were grouped into 1902 gene clusters, showing that loci of the three genomes are not always expressed. A homology search of these gene clusters against a wheat EST database (15964 gene clusters) and a rice full-length cDNA database (21447 gene clusters) revealed that a quarter of the wheat full-length cDNAs were novel. A protein database of Arabidopsis was used to examine the functional classification of these gene clusters. The GC-content in the 5 -UTR region of wheat cDNAs was compared to that of rice. Forty-three genes (3.5% of wheat cDNAs homologous to those of rice) possessed distinct GC-content in the 5 -UTR region, suggesting different breeding behaviors of wheat and rice.