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PubMed2004

A direct repeat sequence associated with the centromeric retrotransposons in wheat.

A high-density BAC filter of Triticum monococcum was screened for the presence of a centromeric retrotransposon using the integrase region as a probe. Southern hybridization to the BAC digests using total genomic DNA probes of Triticum monococcum, Triticum aestivum, and Hordeum vulgare detected differentially hybridizing restriction fragments between wheat and barley. The fragments that hybridized to genomic DNA of wheat but not to that of barley were subcloned. Fluorescence in situ hybridization (FISH) analysis indicated that the clone pHind258 hybridized strongly to centromeric regions in wheat and rye and weakly to those in barley. The sequence of pHind258 was homologous to integrase and long terminal repeats of centromeric Ty3-gypsy retrotransposons of cereal species. Additionally, pHind258 has a pair of 192-bp direct repeats. FISH analysis indicated that the 192-bp repeat probe hybridized to centromeres of wheat and rye but not to those of barley. We found differential FISH signal intensities among wheat chromosomes using the 192-bp probe. In general, the A-genome chromosomes possess strong FISH signals, the B-genome chromosomes possess moderate signals, and the D-genome chromosomes possess weak signals. This was consistent with the estimated copy numbers of the 192-bp repeats in the ancestral species of hexaploid wheat.

Base Sequence↗

PubMed2006

Attempts to induce homoeologous pairing between wheat and Agropyron cristatum genomes.

Agropyron cristatum (2n = 4x = 28, PPPP) possesses potentially valuable traits that could be used in wheat (Triticum aestivum) improvement through interspecific hybridization. Homoeologous pairing between wheat chromosomes and P chromosomes added to wheat in a set of wheat - A. cristatum addition lines was assessed. First, the Ph-suppressing effect of P chromosomes (except 7P) was analyzed. It was concluded that this system is polygenic with no major gene, and consequently, has no prospect in the transfer of alien genes from wild relatives. In a second step, the potential of the deletion ph1b of the Ph1 gene for inducing P-ABD pairing was evaluated. Allosyndetic associations between P and ABD genomes are very rare. This very low level of pairing is likely due to divergence in the repeated sequences between Agropyron and wheat genomes. Development of translocation lines using ionizing radiation seems to be a more suitable technique than homoeologous recombination to exploit the A. cristatum genome in wheat improvement.

Agropyron↗

PubMed2005

Construction of a hexaploid wheat (Triticum aestivum L.) bacterial artificial chromosome library for cloning genes for stripe rust resistance.

A hexaploid wheat (Triticum aestivum L.) bacterial artificial chromosome (BAC) library was constructed for cloning Yr5 and other genes conferring resistance to stripe rust (Puccinia striiformis f. sp. tritici). Intact nuclei from a Yr5 near-isogenic line were used to isolate high molecular weight DNA, which was partially cleaved with HindIII and cloned into pECBAC1 and pIndigoBAC-5 vectors. The wheat BAC library consisted of 422,400 clones arrayed in 1100 micro-titer plates (each plate with 384 wells). Random sampling of 300 BAC clones indicated an average insert size of 140 kb, with a size range from 25 to 365 kb. Ninety percent of the clones in the library had an insert size greater than 100 kb and fewer than 5% of the clones did not contain inserts. Based on an estimated genome size of 15,966 Mb for hexaploid wheat, the BAC library was estimated to have a total coverage of 3.58x wheat genome equivalents, giving approximately 96% probability of identifying a clone representing any given wheat DNA sequence. Twelve BAC clones containing an Yr5 locus-specific marker (Yr5STS7/8) were successfully selected by PCR screening of 3-dimensional BAC pools. The results demonstrated that the T. aestivum BAC library is a valuable genomic resource for positional cloning of Yr5. The library also should be useful in cloning other genes for stripe rust resistance and other traits of interest in hexaploid wheat.

Basidiomycota↗

PubMed2006

Construction of comparative genetic maps of two 4Bs.4Bl-5Rl translocations in bread wheat (Triticum aestivum L.).

The physical length of the rye segment of a 4BS.4BL-5RL translocation derived from the Cornell Wheat Selection 82a1-2-4-7 in a Triticum aestivum 'Chinese Spring' background was measured using genomic in situ hybridization (GISH) and found to be 16% of the long arm. The size of this translocation was similar to previously published GISH measurements of another 4BS.4BL-5RL translocation in a Triticum aestivum 'Viking' wheat background. Molecular maps of both 4BS.4BL-5RL translocations for 2 different wheat backgrounds were developed using RFLP analysis. The locations of the translocation breakpoints of the 2 4BS.4BL-5RL translocations were similar even though they arose in different populations. This suggests a unique property of the region at or near the translocation breakpoint that could be associated with their similarity and spontaneous formation. These segments of rye chromosome 5 also contain a gene for copper efficiency that improves the wheat's ability to cope with low-copper soils. Genetic markers in these maps can also be used to screen for copper efficiency in bread wheat lines derived from the Cornell Wheat Selection 82a1 2-4-7.

Chromosome Mapping↗

PubMed2000

Molecular analyses of a repetitive DNA sequence in wheat (Triticum aestivum L.).

A repetitive sequence designated WE35 was isolated from wheat genomic DNA. This sequence consists of a 320-bp repeat unit and represents approximately 0.002% of the total wheat DNA. It is unidirectionally distributed either continuously or discretely in the genome. Ladder-like banding patterns were observed in Southern blots when the wheat genomic DNA was restricted with endonuclease enzymes EcoRI, HincII, NciI, and NdeI, which is characteristic for tandemly organized sequences. Two DNA fragments in p451 were frequently associated with the WE35 repetitive unit in a majority of lambda wheat genomic clones. A 475-bp fragment homologous to the 5'-end long terminal repeat (LTR) of cereal retroelements was also found in some lambda wheat genomic clones containing the repetitive unit. Physical mapping by fluorescence in situ hybridization (FISH) indicated that one pair of wheat chromosomes could be specifically detected with the WE35 positive probe p551. WE35 can be considered a chromosome-specific repetitive sequence. This repetitive unit could be used as a molecular marker for genetic, phylogenetic, and evolutionary studies in the tribe Triticeae.

Amino Acid Sequence↗

PubMed1982

Synthesis and turnover of proteins and mRNA in germinating wheat embryos.

The most prominent methionine-labeled protein made when cell-free systems are programmed with bulk mRNA from dry wheat embryos has been identified with what may be the most abundant protein in dry wheat embryos. The protein has been brought to purity and has a distinctive amino acid composition, Gly and Glx accounting for almost 40% of the total amino acids. Designated E because of its conspicuous association with early inhibition of dry wheat embryos, the protein and its mRNA are abundant during the "early" phase (0--1 h) of postimbibition development, and easily detected during "lag" phase (1--5 h), but they are almost totally degraded soon after entry into the "growth" phase of development, by about 10 h postimbibition. The most prominent methionine-labeled protein peculiar to the cell-free translational capacity of bulk mRNA from "growth" phase embryos is not detected as a product of in vivo synthesis. Its electrophoretic properties and its time course of emergence, after 5 h postimbibition development, suggest that this major product of cell-free synthesis may be an in vitro counterpart to a prominent methionine-labeled protein made only in vivo, by "growth" phase embryos. Designated G because of its conspicuous association with "growth" phase development, the cell-free product does not comigrate with any prominent dye-stained band in electrophoretic distributions of wheat proteins. The suspected cellular counterpart to G, also, does not comigrate with a prominent dye-stained wheat protein during electrophoresis, and although found in particulate as well as soluble fractions of wheat embryo homogenates it is not concentrated in either nuclei or mitochondria, as isolated.

Amino Acids↗

PubMed2005

Limitations of in situ hybridization with total genomic DNA in routine screening for alien introgressions in wheat.

In situ hybridization with total genomic DNA (GISH) has become a powerful tool in characterization of alien introgressions in wheat. With recent simplification it can now be used in large scale screening for new chromosome constructs. Its level of resolution in routine applications was tested on sets of recombined wheat-rye chromosomes with genetically determined positions of the translocation breakpoints. The resolution level of GISH visualized by an enzymatic color reaction was much lower than that of GISH with fluorescent probes but both techniques failed to reveal the presence of some distally located breakpoints. The limits of resolution for the two methods were at least 9.8 and 3.5 cM of the relative genetic lengths of chromosome arms, respectively, in configurations with proximal rye and terminal wheat segments when rye DNA was used as a probe. When wheat DNA was used as a probe, a terminal wheat segment estimated to be ca. 1.6 cM in length could not be visualized. An example of induced recombination between a chromosome of Agropyron elongatum and wheat illustrates that these resolution limits of GISH may hamper isolation of critical translocation breakpoints in a chromosome engineering effort.

Chromosome Mapping↗

PubMed2005

The effects of a 45x potency of arsenicum album on wheat seedling growth -- a reproduction trial.

BACKGROUND: Independent replications of preclinical investigations of homeopathic potencies are rare. However, they are a necessary tool to determine the relevant factors modulating the effects of homeopathic potencies in preclinical systems. OBJECTIVE: The goal of the present study was to reproduce a trial published in 1997. An Italian group of researchers investigated the effect of Arsenicum album 45x on the growth of wheat which had been previously poisoned with a material dose of Arsenicum album. The homeopathic treatment was associated with increased wheat shoot growth significantly different from the control group (+24%, p < 0.001). MATERIALS AND METHODS: Wheat poisoned with a sublethal dose of Arsenicum album was cultivated in either Arsenicum album 45x, water 45x, or unpotentized water. After 7 days, shoot length was measured. Reproducibility was assessed in eight independent experiments. RESULTS: Arsenicum album 45x significantly inhibited wheat shoot growth (-3%) compared to treatment with unpotentized water and water 45x (p = 0.011 and p = 0.037). Within the experimental series performed in this reproduction trial, the effects of Arsenicum album 45x proofed to be reproducible. The wheat seed species used did not seem to have a significant impact on the experimental outcome. CONCLUSION: The result of this replication trial is a reversal of the original study, since Arsenicum album 45x inhibited wheat shoot growth instead of enhancing it. Nevertheless, high homeopathic potencies may induce statistically significant effects in biological systems. However, the magnitude and direction of these effects seem to depend on yet unknown parameters.

Arsenic Trioxide↗

PubMed2002

Opportunities for nutritionally enhanced maize and wheat varieties to combat protein and micronutrient malnutrition.

Naturally occurring variation detected in the germplasm of maize and wheat, two of the top three cereal crops in the world, provides options for incorporating higher levels of iron, zinc, and beta-carotene into these grains. In addition, quality protein maize (QPM) has been developed from naturally occurring variation; its seed contains enhanced levels of lysine and tryptophan, two essential amino acids lacking in cereals. The International Maize and Wheat Improvement Center, along with its many partners, has identified several maize and wheat varieties with 25% to 30% higher grain iron and zinc concentrations. Wild relatives of wheat have been found to contain some of the highest iron and zinc concentrations in the grains. Although these accessions are often low yielding and have poor grain quality, backcrossing to bread wheat could result in highly nutritious cultivars. Options are now available for conventional and biotechnology-assisted improvement of the nutritional content of maize and wheat germplasm.

Biotechnology↗

PubMed2005

Nonrandom distribution and frequencies of genomic and EST-derived microsatellite markers in rice, wheat, and barley.

BACKGROUND: Earlier comparative maps between the genomes of rice (Oryza sativa L.), barley (Hordeum vulgare L.) and wheat (Triticum aestivum L.) were linkage maps based on cDNA-RFLP markers. The low number of polymorphic RFLP markers has limited the development of dense genetic maps in wheat and the number of available anchor points in comparative maps. Higher density comparative maps using PCR-based anchor markers are necessary to better estimate the conservation of colinearity among cereal genomes. The purposes of this study were to characterize the proportion of transcribed DNA sequences containing simple sequence repeats (SSR or microsatellites) by length and motif for wheat, barley and rice and to determine in-silico rice genome locations for primer sets developed for wheat and barley Expressed Sequence Tags. RESULTS: The proportions of SSR types (di-, tri-, tetra-, and penta-nucleotide repeats) and motifs varied with the length of the SSRs within and among the three species, with trinucleotide SSRs being the most frequent. Distributions of genomic microsatellites (gSSRs), EST-derived microsatellites (EST-SSRs), and transcribed regions in the contiguous sequence of rice chromosome 1 were highly correlated. More than 13,000 primer pairs were developed for use by the cereal research community as potential markers in wheat, barley and rice. CONCLUSION: Trinucleotide SSRs were the most common type in each of the species; however, the relative proportions of SSR types and motifs differed among rice, wheat, and barley. Genomic microsatellites were found to be primarily located in gene-rich regions of the rice genome. Microsatellite markers derived from the use of non-redundant EST-SSRs are an economic and efficient alternative to RFLP for comparative mapping in cereals.

Amino Acid Motifs↗

PubMed2006

Wheat EST resources for functional genomics of abiotic stress.

BACKGROUND: Wheat is an excellent species to study freezing tolerance and other abiotic stresses. However, the sequence of the wheat genome has not been completely characterized due to its complexity and large size. To circumvent this obstacle and identify genes involved in cold acclimation and associated stresses, a large scale EST sequencing approach was undertaken by the Functional Genomics of Abiotic Stress (FGAS) project. RESULTS: We generated 73,521 quality-filtered ESTs from eleven cDNA libraries constructed from wheat plants exposed to various abiotic stresses and at different developmental stages. In addition, 196,041 ESTs for which tracefiles were available from the National Science Foundation wheat EST sequencing program and DuPont were also quality-filtered and used in the analysis. Clustering of the combined ESTs with d2_cluster and TGICL yielded a few large clusters containing several thousand ESTs that were refractory to routine clustering techniques. To resolve this problem, the sequence proximity and "bridges" were identified by an e-value distance graph to manually break clusters into smaller groups. Assembly of the resolved ESTs generated a 75,488 unique sequence set (31,580 contigs and 43,908 singletons/singlets). Digital expression analyses indicated that the FGAS dataset is enriched in stress-regulated genes compared to the other public datasets. Over 43% of the unique sequence set was annotated and classified into functional categories according to Gene Ontology. CONCLUSION: We have annotated 29,556 different sequences, an almost 5-fold increase in annotated sequences compared to the available wheat public databases. Digital expression analysis combined with gene annotation helped in the identification of several pathways associated with abiotic stress. The genomic resources and knowledge developed by this project will contribute to a better understanding of the different mechanisms that govern stress tolerance in wheat and other cereals.

Acclimatization↗

PubMed1982

Effects of gliadin-derived peptides from bread and durum wheats on small intestine cultures from rat fetus and coeliac children.

Peptic-tryptic-cotazym (PTC) digests were obtained, simulating in vivo protein digestion, from albumin, globulin, gliadin and glutenin preparations from hexaploid (bread) wheat as well as from diploid (monococcum) and tetraploid (durum) wheat gliadins. The digest from bread wheat gliadins reversibly inhibited in vitro development and morphogenesis of small intestine from 17-day-old rat fetuses, whereas all the other digests (obtained both from nongliadin fractions and from gliadins from other wheat species) were inactive. The PTC-digest from bread wheat gliadins was also able to prevent recovery of and to damage the in vitro cultured small intestinal mucosa from patients with active coeliac disease (gluten-induced entheropathy). The PTC-digest from durum wheat gliadins caused a much less adverse effect on this human pathologic tissue culture system.

Animals↗

PubMed1999

Homologous chromosome pairing in wheat.

Bread wheat is a hexaploid (AABBDD, 2n=6x=42) containing three related ancestral genomes, each having 7 chromosomes, giving 42 chromosomes in diploid cells. During meiosis true homologues are correctly associated in wild-type wheat, but a degree of association of related chromosomes (homoeologues) occurs in a mutant (ph1b). We show that the centromeres are associated in non-homologous pairs in all floral tissues studied, both in wild-type wheat and the ph1b mutant. The non-homologous centromere associations then become homologous premeiotically in wild-type wheat in both meiocytes and the tapetal cells, but not in the mutant. In wild-type wheat, the homologues are colocalised along their length at this stage, but the telomeres remain distinct. A single telomere cluster (bouquet) is formed in the meiocytes only by the onset of leptotene. The sub-telomeric regions of the homologues associate as the telomere cluster forms. The homologous associations at the telomeres and centromeres are maintained through meiotic prophase, although, during leptotene, the two homologues and also the sister chromatids within each homologue are separate along the rest of their length. As meiosis progresses, first the sister chromatids and then the homologues associate intimately. In wild-type wheat, first the centromere grouping, then the bouquet disperse by the end of zygotene.

Meiosis↗

PubMed2001

Single nucleotide polymorphisms in an STS region linked to the Ncc-tmp1A locus are informative for characterizing the differentiation of chromosome 1A in wheat.

Homoeoalleles of Ncc confer nucleus-cytoplasm (NC) compatibility on NC hybrids of wheat with the D plasmon of Aegilops squarrosa. To dissect the chromosomal region containing Ncc, a RAPD marker linked to the Ncc-tmplA locus, which is located on chromosome 1A of T timopheevi, was sequenced and converted to a PCR-based sequence-tagged-site (STS) marker. Five single nucleotide polymorphisms (SNPs) between T timopheevi and T turgidum. were detected in a 509-bp genomic DNA fragment. Based on the SNPs, the STS alleles in 164 accessions from emmer wheat, timopheevi wheat and two einkorn wheats, T. urartu and T. boeoticum were surveyed by PCR-RFLP analysis. The sequence comparisons and PCR-RFLP analyses revealed nine alleles based on six SNPs. These SNPs were highly conserved within each group of wheat, and all groups could be distinguished by particular combinations of the SNPs. All accessions of T. urartu had one unique STS allele as compared with the others. Our results indicate that the SNPs in the STS marker linked to the Ncc-tmplA locus would be informative for studies of the differentiation of chromosome 1A in wheat.

Alleles↗

PubMed2006

Mortality from ischemic heart disease and diabetes mellitus (type 2) in four U.S. wheat-producing states: a hypothesis-generating study.

In this ecologic study I examined ischemic heart disease (IHD) and diabetes mortality in rural agricultural counties of Minnesota, Montana, North Dakota, and South Dakota, in association with environmental exposure to chlorophenoxy herbicides, using wheat acreage as a surrogate exposure. I collected data on agricultural land use and 1979-1998 mortality from the U.S. Department of Agriculture and the Centers for Disease Control and Prevention websites, respectively. Counties were grouped based on percentage of land area dedicated to wheat farming. Poisson relative risks (RR) and 95% confidence intervals (CIs), comparing high- and medium- with low-wheat counties, were obtained for IHD, the subcategories acute myocardial infarction (AMI) and coronary atherosclerosis (CAS), and diabetes, adjusting for sex, age, mortality cohort, and poverty index. Mortality from IHD was modestly increased (RR = 1.08; 95% CI, 1.04-1.12). Analyses of its two major forms were more revealing. Compared with low-wheat counties, mortality in high-wheat counties from AMI increased (RR = 1.20; 95% CI, 1.14-1.26), and mortality from CAS decreased (RR = 0.89; 95% CI, 0.83-0.96). Mortality from AMI was more pronounced for those < 65 years of age (RR = 1.31; 95% CI 1.22-1.39). Mortality from type 2 diabetes increased (RR = 1.16; 95% CI, 1.08-1.24). These results suggest that the underlying cause of mortality from AMI and type 2 diabetes increased and the underlying cause of mortality from CAS decreased in counties where a large proportion of the land area is dedicated to spring and durum wheat farming. Firm conclusions on causal inference cannot be reached until more definitive studies have been conducted.

Adolescent↗

PubMed2003

Examination of spectral pretreatments for partial least-squares calibrations for chemical and physical properties of wheat.

Use of near-infrared (NIR) diffuse reflectance on ground wheat meal for prediction of protein content is a well-accepted practice. Although protein content has a strong bearing on the suitability of wheat (Triticum aestivum L.) for processed foods, wheat quality, as largely influenced by the configuration and conformation of the monomeric and polymeric endosperm storage proteins, is also of great importance to the food industry. The measurement of quality by NIR, however, has been much less successful. The present study examines the effects and trends of applying mathematical transformations (pretreatments) to NIR spectral data before partial least-squares (PLS) regression. Running mean smooths, Savitzky-Golay second derivatives, multiplicative scatter correction, and standard normal variate transformation, with and without detrending, were systematically applied to an extensive set of hard red winter wheat and hard white wheat grown over two seasons. The studied properties were protein content, sodium dodecyl sulfate (SDS) sedimentation volume, number of hours during grain fill at temperature <24 degrees C, and number of hours during grain fill at temperature >32 degrees C. The size of the convolution window used to perform a smooth or second derivative was also examined. The results indicate that for easily modeled properties such as protein content, the importance of pretreatment was lessened, whereas for the more difficult-to-model properties, such as SDS sedimentation volume, wide-window (>20 points) smooth or derivative convolutions were important in maximizing calibration performance. By averaging 30 PLS cross-validation trial statistics (standard error) for each property, we were able to ascertain the inherent modeling ability of each wheat property.

Calibration↗

PubMed1982

Pulmonary reaction to durum wheat; a constituent of grain dust.

To identify constituents of grain dust responsible for grain handlers' respiratory symptoms, 11 volunteer grain elevator workers underwent inhalation provocation tests with extracts of durum wheat, durum wheat airborne dust, and grain insects and mites. Factors that might influence the host response to the challenge were assessed. Five of the 11 subjects showed a greater than 20 percent decrement in FEV1 after inhalation of durum wheat extracts (airways reaction). The bronchial reactions were immediate in 1/5 and late in 4/5. These airway reactions were blocked by sodium cromoglycate. Only one subject showed airway reaction to durum wheat dust extract, and none reacted to mites or insect extracts. There was no change in DLCO, temperature, or in total C3 complement blood levels, nor was there evidence of activation of complement by the alternate or classic pathway. The airway response was not always related to the atopic status of the individual. The reaction is more likely to occur in subjects with preexisting airway obstruction and nonspecific bronchial hyperreactivity. Durum wheat has been identified as an inducer of occupational asthma in grain handlers. This reaction is probably due to specific or nonspecific mediator release. There was no apparent parenchymal or systemic reaction or complement activation detectable in the subjects' sera after inhalation of durum wheat extracts.

Adult↗

PubMed2004

Alkaline peroxide mechanical pulping of wheat straw with enzyme treatment.

Alkaline peroxide mechanical pulping (APMP) of wheat straw with enzyme treatment was studied. Instead of direct enzyme pretreatment on wheat straw, an alternative treatment method was used, in which coarse pulps from refiner defibrated wheat straw rather than wheat straw were pretreated with a crude enzyme containing mainly xylanase, then impregnated with alkaline H2O2 solution and further refined. The optimum conditions of enzyme treatment were xylanase dosage of 10-15 IU/g of oven-dried wheat straw, 90 min, 50-60 degrees C, pulp consistency of 5-10%, and initial pH of 5.0, and those for chemical impregnation were 6% NaOH, 70-80 degrees C, 60-90 min, and 4 to 5% H2O2. Enzyme treatment improved pulpability of wheat straw by the APMP process, and final pulp quality such as brightness, breaking length, and burst index of pulp. Pulp from the APMP process with enzyme treatment could be bleached to a brightness of 70.5% ISO by two-stage H2O2 bleaching sequence with only 4% H2O2, and breaking length of the bleach pulp reached 4470 m

Alkalies↗