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PubMed2006

Radiocaesium activity concentrations in wheat grains in the Republic of Croatia for 1965-2003 and dose assessment.

Results of systematic, long-term measurements of (137)Cs activities in wheat for the period 1965-2003 are summarized. Radiocaesum fallout activities affect wheat activity concentrations, the coefficient of correlation being 0.91. In the observed period, the highest activity of (137)Cs deposited by fallout, 6321 Bq m(-2), was recorded in 1986, i.e., in the year of Chernobyl accident, causing peak (137)Cs activity concentration in wheat of 38.0 +/- 13.0 Bq kg(-1). After the Chernobyl nuclear accident the (134)Cs:(137)Cs activity ratio in wheat was approximately 0.5, and did not differ from the value found in other environmental samples. The transfer coefficient from (137)Cs fallout deposition to wheat was calculated to be 8.6 x 10(-3) Bq y kg(-1) per Bq m(-2), indicating the low transfer of radiocaesium from fallout to wheat. The upper limit for the collective effective dose for the Croatian population due to (137)Cs and (134)Cs ingestion by wheat and wheat products consumption for period 1965-2003 was estimated to be 665 person-Sv, the upper limit for the annual collective effective dose in 2003 being only about 0.061 person-Sv.

Cesium Radioisotopes↗
PubMed2005

A microarray-based comparative analysis of gene expression profiles during grain development in transgenic and wild type wheat.

Global, comparative gene expression analysis is potentially a very powerful tool in the safety assessment of transgenic plants since it allows for the detection of differences in gene expression patterns between a transgenic line and the mother variety. In the present study, we compared the gene expression profile in developing seeds of wild type wheat and wheat transformed for endosperm-specific expression of an Aspergillus fumigatus phytase. High-level expression of the phytase gene was ensured by codon modification towards the prevalent codon usage of wheat genes and by using the wheat 1DX5HMW glutenin promoter for driving transgene expression. A 9K wheat unigene cDNA microarray was produced from cDNA libraries prepared mainly from developing wheat seed. The arrays were hybridised to flourescently labelled cDNA prepared from developing seeds of the transgenic wheat line and the mother variety, Bobwhite, at three developmental stages. Comparisons and statistical analyses of the gene expression profiles of the transgenic line vs. that of the mother line revealed only slight differences at the three developmental stages. In the few cases where differential expression was indicated by the statistical analysis it was primarily genes that were strongly expressed over a shorter interval of seed development such as genes encoding storage proteins. Accordingly, we interpret these differences in gene expression levels to result from minor asynchrony in seed development between the transgenic line and the mother line. In support of this, real time PCR validation of results from selected genes at the late developmental stage could not confirm differential expression of these genes. We conclude that the expression of the codon-modified A. fumigatus phytase gene in the wheat seed had no significant effects on the overall gene expression patterns in the developing seed.

6-Phytase↗
PubMed2007

A wheat genomic DNA fragment reduces pollen transmission of maize transgenes by reducing pollen viability.

A genomic DNA fragment from wheat carrying the Glu-1Dx5 gene has been shown to exhibit reduced pollen transmission in transgenic maize. To localize the region of the DNA fragment responsible for this reduced pollen transmission, we produced transgenic maize plants in which the wheat genomic DNA proximal to the 1Dx5 coding sequence was replaced with the maize 27 kDa gamma-zein promoter. Like the wheat promoter-driven Glu-1Dx5 transgene, this zein promoter-driven transgene functioned to produce 1Dx5 in maize endosperm. However, with the zein promoter-driven transgene, pollen transmission of the transgene loci was normal in most self- and cross-pollinations. We concluded that the wheat genomic DNA proximal to the wheat 1Dx5 coding sequence was required for reduced pollen transmission of the transgene in maize. In two of four transformation events of the wheat promoter-driven construct examined, pollen exhibited two morphological classes. In one class, pollen was normal in morphology and displayed average viability, and in the second, pollen was reduced in size and did not germinate on artificial media. DNA from the transgene was detectable in mature pollen from plants with reduced pollen transmission of transgene loci. To explain these observations, we hypothesize that elements within the transgene construct interfere with pollen development. We demonstrated that the wheat genomic DNA fragment can be used to control pollen transmission of an herbicide resistance transgene genetically linked to it. The wheat genomic DNA fragment may contain elements that are useful for controlling pollen transmission of transgene loci in commercial maize grain and seed production.

DNA↗
PubMed1978

Effects of wheat germ agglutinin and concanavalin A on parameters of highly purified sodium-potassium adenosine triphosphatases from Squalus acanthias and Electrophorus electricus.

The effects of two lectins, wheat germ agglutinin and concanavalin A, were studied on a variety of parameters of two highly purified (Na+ + K+)-ATPases (ATP phosphohydrolase, EC 3.6.1.3), from the rectal salt gland of Squalus acanthias and from the electroplax of Electrophorus electricus. Both lectins agglutinated the rectal gland enzyme equally, but wheat germ agglutinin inhibited (Na+ + K+)-ATPase activity much more. The electroplax enzyme was only marginally agglutinated and inhibited by the lectins. Neuraminidase treatment of the rectal gland (Na+ + K+)-ATPase had no effect on germ agglutinin inhibition. The inhibition of the rectal gland (Na+ + K+)-ATPase by wheat germ agglutinin could be reversed by N,N'-diacetylchitobiose, which has a high affinity for wheat germ agglutinin. Neither ouabain inhibition nor ouabain binding to the rectal gland enzyme was affected by wheat germ agglutinin. The p-nitrophenylphosphatase activity of the rectal gland enzyme was not inhibited by wheat germ agglutinin. Na+-ATPase activity, which reflects ATP binding and phosphorylation at the substrate site was inhibited by wheat germ agglutinin and this inhibition was reversed by potassium. Evidence is cited (Pennington, J. and Hokin, L.E., in preparation) that the inhibition of the (Na+ + K+)-ATPase by wheat germ agglutinin is due to binding to the glycoprotein subunit.

Animals↗
PubMed1989

Odor volatiles associated with microflora in damp ventilated and non-ventilated bin-stored bulk wheat.

Western hard red spring wheat, stored at 20 and 25% moisture contents for 10 months during 1985-86, was monitored for biotic and abiotic variables in 10 unheated bins in Winnipeg, Manitoba. The major odor volatiles identified were 3-methyl-1-butanol, 3-octanone and 1-octen-3-ol. The production of these volatiles was associated and correlated with microfloral infection. Ventilation, used for cooling and drying of grain, disrupted microfloral growth patterns and production of volatiles. The highest levels of 3-methyl-1-butanol occurred in 25% moisture content wheat infected with bacteria, Penicillium spp. and Fusarium spp. In non-ventilated (control) bins with 20% moisture content wheat, 3-methyl-1-butanol was correlated with infection by members of the Aspergillus glaucus group and bacteria. In control bins, 1-octen-3-ol production was correlated with infection of wheat of both moisture contents by Penicillium spp. The fungal species, isolated from damp bin-stored wheat and tested for production of odor volatiles on wheat substrate, included Alternaria alternata (Fr.) Keissler, Aspergillus repens (Corda) Saccardo, A. flavus Link ex Fries, A. versicolor (Vuill.) Tiraboschi, Penicillium chrysogenum Thom, P. cyclopium Westling, Fusarium moniliforme Sheldon, F. semitectum (Cooke) Sacc. In the laboratory, fungus-inoculated wheat produced 3-methyl-1-butanol; 3-octanone and 1-octen-3-ol were also produced, but less frequently. Two unidentified bacterial species isolated from damp wheat and inoculated on agar produced 3-methyl-1-butanol.

Alcohols↗
PubMed1993

Studies on the aetiology of coeliac disease: no evidence for lectin-like components in wheat gluten.

In an approach to examine the lectin-hypothesis in the pathogenesis of coeliac disease, the presence of lectin-like components in three wheat gluten preparations known to induce coeliac disease, gliadin, Frazer fraction III and an acetic acid/ethanol extract of gluten, was investigated. Lectin-like components in these wheat gluten preparations were traced in binding studies employing a variety of model glycoproteins glycosylated with the different types of N-linked oligosaccharides, i.e., those of the high mannose-, complex- and hybrid-type. Binding affinity of wheat proteins to these glycoproteins was analyzed by affinity dotting and blotting techniques and was compared to that of the well characterized lectins Galanthus nivalis agglutinin, Concanavalin A and wheat germ agglutinin. Though the three wheat gluten preparations exhibited binding reactivity for distinct model glycoproteins, no correlation was found between the type of N-glycosylation of the model glycoproteins and their binding capability to the different wheat gluten preparations. Moreover, binding of the three gluten preparations to the model glycoproteins could not be inhibited by competitive saccharides (methyl-alpha-D-mannopyranoside, N-acetyl-D-glucosamine, mannan). Enzymatic deglycosylation of the ligand glycoproteins with endo-beta-N-acetylglucosaminidase H (Endo H, EC 3.2.1.96) or peptide N-glycosidase F (PNGase F, EC 3.5.1.52) abolished their binding reactivity for the plant lectins, but did not affect binding of the wheat gluten preparations. These results give no evidence for the presence of lectin-like components in wheat gluten preparations and do question the 'lectin hypothesis' of coeliac disease.

Amidohydrolases↗
PubMed2006

Influence of supplemental dietary sprouted wheat on reproduction in artificially inseminated doe rabbits.

The sprouted wheat contains great amounts of 6-methoxybenzoxazolinone (6-MBOA) a phenol compound that stimulates reproduction in certain small wild herbivorous mammals. The objective of the present study was to evaluate the effect of dietary sprouted wheat as supplement on reproduction in artificially inseminated doe rabbits. Two-month-old New Zealand White doe rabbits (n = 48) were randomly allocated to one of two treatments: (1) pelleted diet plus sprouted wheat for 6 consecutive days prior to service, (2) pelleted diet only (control). First insemination occurred when does reach 3200g body weight and bred 6 days after parturition across 6 months period during summer and autumn. Records from 41 does completing the experiment accounted for 192 inseminations and 142 kindlings equivalent to 4.6 +/- 0.15 and 3.5 +/- 0.15 litters per doe, respectively. Mean daily intake of sprouted wheat on wet and dry matter bases were 196.1 +/- 7.5 and 75.4 +/- 2.9g, respectively. The number of young born produced per doe during the trail was significantly (P = 0.02) greater in does fed sprouted wheat (28.1 +/- 1.2 versus 23.6 +/ -1.3 control). Does fed sprouted wheat had 0.65 +/- 0.06 receptivity rate at AI over 28 per cent greater (P = 0.001) than does in the control treatment. Sexual receptivity was not influenced by physiological status of does and season (P > 0.05). Diet and season had no effect (P>0.05) on kindling rate. However, physiological status had an effect (P = 0.002) on this variable. Kindling rates for nulliparous, lactating and non-lactating does were 0.95 +/- 0.08, 0.63 +/- 0.04 and 0.78 +/ -0.11, respectively. Sexually receptive does had a greater (P = 0.0001) kindling rate (0.95 +/- 0.05) than non-receptive females (0.63 +/-0.05). Does fed sprouted wheat produced larger (P = 0.02) litters than those in the control group: 7.7 +/- 0.30 and 6.8 +/- 0.32, respectively. There was an effect of season (P = 0.04) on the size of the litter at birth. Largest litters were born during autumn (7.9 +/- 0.37) than during summer (6.6 +/- 0.41). Receptive does had more (P = 0.002) young in the litter (7.9 +/- 0.28) than non-receptive (6.6 +/- 0.35). Feeding sprouted wheat as a source of biological 6-MBOA enhanced sexual receptivity and prolificacy in artificially inseminated doe rabbits bred in summer and autumn.

Animals↗
PubMed2005

Molecular cloning and functional analysis of a novel 6&1-FEH from wheat (Triticum aestivum L.) preferentially degrading small graminans like bifurcose.

Like barley and other cereals, wheat (Triticum aestivum L.) accumulates branched graminan-type fructans containing both beta-(2,1) and beta-(2,6) fructosyl linkages, mainly with a quite low degree of polymerization (DP). 1&6-kestotetraose (bifurcose) is the major fructan oligosaccharide accumulating in crown tissues and leaves of cereals exposed to chilling. The fructan exohydrolase (FEH) cDNAs 1-FEH w1 and w2 were previously cloned from wheat crowns sampled in mid-November. Here, we report the cloning and functional analysis of another FEH cDNA from a mid-November wheat crown cDNA library. The cDNA encodes a long open reading frame (ORF) of 595 amino acids. Like other FEHs, it has a low iso-electric point (5.2) and it groups together with cell-wall type invertases and not with vacuolar invertases. The deduced amino acid sequence shows 67% identity to wheat 1-FEH w1 and w2. Functional characterization of the recombinant proteins in Pichia pastoris demonstrated that the recombinant enzyme had FEH activity towards the pure compounds 1-kestose, 6-kestose, 1,1-nystose and 1,1,1-kestopentaose. However, when incubated with its putative natural substrates (a mixture of low DP graminans from wheat crowns), it was shown that 1&6-kestotetraose (bifurcose) was preferentially removed from the graminan mixture. High DP wheat graminan and bacterial levan were only poor substrates. No hydrolase activities could be detected towards sucrose and high DP inulin, convincingly demonstrating that the enzyme is not a classic invertase or 1-FEH. The enzyme was termed 6&1-FEH w1. Northern blot analyses showed that 6&1-FEH w1 was expressed in crown tissue from autumn through winter under snow, while the expression levels in leaves were minimal or not detectable. The results strongly suggest that this unique FEH might play an important role in the degradation of branched, low DP wheat graminan (like bifurcose) in wheat crowns in the high fructan content season.

Amino Acid Sequence↗
PubMed2005

Selenium in Australia: selenium status and biofortification of wheat for better health.

Selenium (Se) is an essential micronutrient for humans and animals, but is deficient in at least a billion people worldwide. Wheat (Triticum aestivum L.) is a major dietary source of Se. The largest survey to date of Se status of Australians found a mean plasma Se concentration of 103 microg/l in 288 Adelaide residents, just above the nutritional adequacy level. In the total sample analysed (six surveys from 1977 to 2002; n = 834), plasma Se was higher in males and increased with age. This study showed that many South Australians consume inadequate Se to maximise selenoenzyme expression and cancer protection, and indicated that levels had declined around 20% from the 1970s. No significant genotypic variability for grain Se concentration was observed in modern wheat cultivars, but the diploid wheat Aegilops tauschii L. and rye (Secale cereale L.) were higher. Grain Se concentrations ranged 5-720 microg/kg and it was apparent that this variation was determined mostly by available soil Se level. Field trials, along with glasshouse and growth chamber studies, were used to investigate agronomic biofortification of wheat. Se applied as sodium selenate at rates of 4-120 g Se/ha increased grain Se concentration progressively up to 133-fold when sprayed on soil at seeding and up to 20-fold when applied as a foliar spray after flowering. A threshold of toxicity of around 325 mg Se/kg in leaves of young wheat plants was observed, a level that would not normally be reached with Se fertilisation. On the other hand sulphur (S) applied at the low rate of 30 kg/ha at seeding reduced grain Se concentration by 16%. Agronomic biofortification could be used by food companies as a cost-effective method to produce high-Se wheat products that contain most Se in the desirable selenomethionine form. Further studies are needed to assess the functionality of high-Se wheat, for example short-term clinical trials that measure changes in genome stability, lipid peroxidation and immunocompetence. Increasing the Se content of wheat is a food systems strategy that could increase the Se intake of whole populations.

Animals↗
PubMed2001

Safe storage time of high moisture wheat.

Deterioration rates were determined for 15-19% moisture content (m.c., wet basis) wheat (Triticum aestivum L. cv. 'Barrie') stored at constant temperatures or with a step decrease in storage temperatures. Deterioration rates were determined by measuring germination capacity of the grain and respiration rates of grain and microorganisms. Safe storage time was defined as the time for germination to decrease to 90%. Safe storage times of 19% m.c. wheat stored at constant temperatures ranged from 2.5 d at 30 and 35 degrees C to 37 d at 10 degrees C. Deterioration rates of 19% m.c. wheat stored with a step decrease in storage temperatures (35-25, 30-20, 25-20, and 20-15 degrees C) were determined and safe storage times were satisfactorily predicted. Safe storage times of 17% m.c. wheat were 5, 7, and 15 d at 35, 30, and 25 degrees C, respectively. Respiration rates and germination percentages of 15 and 16% m.c. wheat stored at 25 degrees C remained constant for 70 d. The respiration rates of 17-19% m.c. wheat at 25 degrees C increased while the germination percentages decreased with storage time. Germination dropped from 98 to 92-89% when the dry matter losses were about 0.05% and visible mould occurred when the dry matter losses were about 0.1% in 17-19% m.c. wheat. Safe storage times of 17% m.c. wheat stored at 35-25 degrees C were compared with those determined in similar previous work with cultivars 'Domain' and 'Katepwa'. 'Domain' had the longest and 'Barrie' had the shortest storage times.

Journal Article↗
PubMed1998

Photosynthetic capacity and dry mass partitioning in dwarf and semi-dwarf wheat (Triticum aestivum L.).

Efficient use of space and high yields are critical for long-term food production aboard the International Space Station. The selection of a full dwarf wheat (less than 30 cm tall) with high photosynthetic and yield potential is a necessary prerequisite for growing wheat in the controlled, volume-limited environments available aboard long-term spaceflight missions. This study evaluated the photosynthetic capacity and carbon partitioning of a full-dwarf wheat cultivar, Super Dwarf, which is routinely used in spaceflight studies aboard U.S. space shuttle and NASA/Mir missions and made comparisons with other dwarf and semi-dwarf wheat cultivars utilized in other ground-based studies in plant space biology. Photosynthetic capacity of the flag leaf in two dwarf (Super Dwarf, BB-19), and three semi-dwarf (Veery-10, Yecora Rojo, IBWSN 199) wheat cultivars (Triticum aestivum L.) was assessed by measuring: net maximum photosynthetic rate, RuBP carboxylation efficiency, chlorophyll concentration and flag leaf area. Dry mass partitioning of carbohydrates to the leaves, sheaths, stems and ear was also assessed. Plants were grown under controlled environmental conditions in three replicate studies: slightly enriched CO2 (370 micromoles mol-1), high photosynthetic photon flux (1000 micromoles m-2 s-1; 58 mol m-2 d-1) for a 16 h photoperiod, 22/15 degrees C day/night temperatures, ample nutrients and water provided by one-half strength Hoagland's nutrient solution (Hoagland and Arnon, 1950). Photosynthetic capacity of the flag leaf was determined at anthesis using net CO2 exchange rate versus internal CO2 concentration curves measured under saturating light (2000 micromoles m-2 s-1) and CO2 (1000 micromoles mol-1). Dwarf wheat cultivars had greater photosynthetic capacities than the taller semi-dwarfs, they averaged 20% higher maximum net photosynthetic rates compared to the taller semi-dwarfs, but these higher rates occurred only at anthesis, had slightly greater carboxylation efficiencies and significantly increased chlorophyll concentrations per unit leaf area. The reduced-height wheat had significantly less dry mass fraction in the stem but greater dry mass partitioned to the ear than the taller semi-dwarfs (Yecora rojo, IBWSN-199). Studies with detached heads confirm that the head is a significant sink in the shorter wheat cultivars.

Biomass↗
PubMed2005

Phytochemicals and antioxidant activity of milled fractions of different wheat varieties.

The health-promoting effects of whole-grain consumption have been attributed in part to their unique phytochemical contents and profiles that complement those found in fruits and vegetables. Wheat is an important component of the human diet; however, little is known about the phytochemical profiles and total antioxidant activities of milled fractions of different wheat varieties. The objectives of this study were to investigate the distribution of phytochemicals (total phenolics, flavonoids, ferulic acid, and carotenoids) and to determine hydrophilic and lipophilic antioxidant activity in milled fractions (endosperm and bran/germ) of three different wheat varieties, two of which were grown in two environments. Grain samples of each of the wheat varieties were milled into endosperm and bran/germ fractions. Each fraction was extracted and analyzed for total phenolics, ferulic acid, flavonoids, carotenoid contents, and hydrophilic and lipophilic antioxidant activities. Total phenolic content of bran/germ fractions (2867-3120 micromol of gallic acid equiv/100 g) was 15-18-fold higher (p < 0.01) than that of respective endosperm fractions. Ferulic acid content ranged from 1005 to 1130 micromol/100 g in bran/germ fractions and from 15 to 21 micromol/100 g in the endosperm fractions. The bran/germ fraction flavonoid content was 740-940 micromol of catechin equiv/100 g. On average, bran/germ fractions of wheat had 4-fold more lutein, 12-fold more zeaxanthin, and 2-fold more beta-cryptoxanthin than the endosperm fractions. Hydrophilic antioxidant activity of bran/germ samples (7.1-16.4 micromol of vitamin C equiv/g) was 13-27-fold higher than that of the respective endosperm samples. Similarly, lipophilic antioxidant activity was 28-89-fold higher in the bran/germ fractions (1785-4669 nmol of vitamin E equiv/g). Hydrophilic antioxidant activity contribution to the total antioxidant activity (hydrophilic + lipophilic) was >80%. In whole-wheat flour, the bran/germ fraction contributed 83% of the total phenolic content, 79% of the total flavonoid content, 51% of the total lutein, 78% of the total zeaxanthin, 42% of the total beta-cryptoxanthin, 85% of the total hydrophilic antioxidant activity, and 94% of the total lipophilic antioxidant activity. Our results showed that different milled fractions of wheat have different profiles of both hydrophilic and lipophilic phytochemicals. These findings provide information necessary for evaluating contributions to good health and disease prevention from whole-wheat consumption.

Antioxidants↗
PubMed2006

Herbicidal effects of soil-incorporated wheat.

The hydroxamic acid 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) and the benzoxazolinones benzoxazolin-2-one (BOA) and 6-methoxybenzoxazolin-2-one (MBOA) have been identified as important allelochemicals in wheat. This study examines the possibility of exploiting the allelopathic properties of wheat as a weed control strategy by cultivating wheat as a precrop and incorporating plant residues into the soil before the next crop is sown. Different wheat varieties were cultivated in field plots during two seasons in both conventional and organic farming systems. Plants were sampled at various growth stages, and their contents of DIMBOA, MBOA, and BOA were determined by chemical analyses. The wheat samples were incorporated into soil, and the effect on germination and growth of 12 different weed species was examined in pot experiments under controlled conditions. In some cases significant effects were obtained, but the results were inconsistent and the effects were not correlated to the content of DIMBOA, MBOA, and BOA in the incorporated wheat plants. ED50 doses of the pure compounds were estimated in dose-response experiments in Petri dishes, and these turned out to be much higher than the predicted maximum concentrations of DIMBOA, MBOA, and BOA in the soil water following incorporation. The study shows that a prerequisite for exploiting the incorporation of wheat residues as a weed control strategy is the development of wheat varieties with an increased content of allelochemicals.

Benzoxazines↗
PubMed2006

Variation of wheat root exudates under aluminum stress.

The wheat (Triticum aestivum L.) cultivar Yangzhou 158 was used as a reference. The wheat root exudates were collected using a hydroponic mode. The changes of the electrolytes, H+, sugar, organic acids, amino acids, and secondary metabolites in wheat root exudates induced by aluminum (Al) were studied. The research results show that Al stress affects wheat root exudation. The secreted electrolytes and sugar increase with the increasing of the external Al3+ concentration. The total amount of secreted amino acids has a specific correlation with the external Al3+ concentration. At first, the amino acids secrete normally, but when Al3+ concentration is over 10 mg.L-1, the amino acid constitution varies obviously. Under Al stress, some original secondary metabolites disappear gradually, and other new secondary metabolites release simultaneously. Increasing the external Al3+ concentration gradually stimulates the exudation of organic acids. The organic acid levels in the wheat root zone increase in response to Al treatments. Active Al ions are accumulated in wheat roots. This Al-dependent variation in wheat root exudates suggests a specific Al-induced response of the wheat.

Aluminum↗
PubMed2002

Cloning of thioredoxin h reductase and characterization of the thioredoxin reductase-thioredoxin h system from wheat.

Thioredoxins h are ubiquitous proteins reduced by NADPH- thioredoxin reductase (NTR). They are able to reduce disulphides in target proteins. In monocots, thioredoxins h accumulate at high level in seeds and show a predominant localization in the nucleus of seed cells. These results suggest that the NTR-thioredoxin h system probably plays an important role in seed physiology. To date, the study of this system in monocots is limited by the lack of information about NTR. In the present study, we describe the cloning of a full-length cDNA encoding NTR from wheat ( Triticum aestivum ). The polypeptide deduced from this cDNA shows close similarity to NTRs from Arabidopsis, contains FAD- and NADPH-binding domains and a disulphide probably interacting with the disulphide at the active site of thioredoxin h. Wheat NTR was expressed in Escherichia coli as a His-tagged protein. The absorption spectrum of the purified recombinant protein is typical of flavoenzymes. Furthermore, it showed NADPH-dependent thioredoxin h reduction activity, thus confirming that the cDNA clone reported in the present study encodes wheat NTR. Using the His-tagged NTR and TRXhA (wheat thioredoxin h ), we successfully reconstituted the wheat NTR-thioredoxin h system in vitro, as shown by the insulin reduction assay. A polyclonal antibody was raised against wheat NTR after immunization of rabbits with the purified His-tagged protein. This antibody efficiently detected a single polypeptide of the corresponding molecular mass in seed extracts and it allowed the analysis of the pattern of accumulation of NTR in different wheat organs and developmental stages. NTR shows a wide distribution in wheat, but, surprisingly, its accumulation in seeds is low, in contrast with the level of thioredoxins h.

Amino Acid Sequence↗
PubMed2004

Genome analysis at different ploidy levels allows cloning of the powdery mildew resistance gene Pm3b from hexaploid wheat.

In wheat, race-specific resistance to the fungal pathogen powdery mildew (Blumeria graminis f. sp. tritici) is controlled by the Pm genes. There are 10 alleles conferring resistance at the Pm3 locus (Pm3a to Pm3j) on chromosome 1AS of hexaploid bread wheat (Triticum aestivum L.). The genome of hexaploid wheat has a size of 1.6 x 1010 bp and contains more than 80% of repetitive sequences, making positional cloning difficult. Here, we demonstrate that the combined analysis of genomes from wheat species with different ploidy levels can be exploited for positional cloning in bread wheat. We have mapped the Pm3b gene in hexaploid wheat to a genetic interval of 0.97 centimorgan (cM). The diploid T. monococcum and the tetraploid T. turgidum ssp. durum provided models for the A genome of hexaploid wheat and allowed to establish a physical contig spanning the Pm3 locus. Although the haplotypes at the Pm3 locus differed markedly between the three species, a large resistance gene-like family specific to wheat group 1 chromosomes was consistently found at the Pm3 locus. A candidate gene for Pm3b was identified using partial sequence conservation between resistant line Chul and T. monococcum cv. DV92. A susceptible Pm3b mutant, carrying a single-base pair deletion in the coding region of the candidate gene was isolated. When tested in a single cell transformation assay, the Pm3b candidate gene conferred race-specific resistance to powdery mildew. These results demonstrate that the candidate gene, a member of the coiled-coil nucleotide binding site leucine-rich repeat (NBS-LRR) type of disease resistance genes, is the Pm3b gene.

Alleles↗
PubMed2005

Three genomes differentially contribute to the biosynthesis of benzoxazinones in hexaploid wheat.

Hexaploid wheat (Triticum aestivum) accumulates benzoxazinones (Bxs) as defensive compounds. Previously, we found that five Bx biosynthetic genes, TaBx1-TaBx5, are located on each of the three genomes (A, B, and D) of hexaploid wheat. In this study, we isolated three homoeologous cDNAs of each TaBx gene to estimate the contribution of individual homoeologous TaBx genes to the biosynthesis of Bxs in hexaploid wheat. We analyzed their transcript levels by homoeolog- or genome-specific quantitative RT-PCR and the catalytic properties of their translation products by kinetic analyses using recombinant TaBX enzymes. The three homoeologs were transcribed differentially, and the ratio of the individual homoeologous transcripts to total homoeologous transcripts also varied with the tissue, i.e., shoots or roots, as well as with the developmental stage. Moreover, the translation products of the three homoeologs had different catalytic properties. Some TaBx homoeologs were efficiently transcribed, but the translation products showed only weak enzymatic activities, which inferred their weak contribution to Bx biosynthesis. Considering the transcript levels and the catalytic properties collectively, we concluded that the homoeologs on the B genome generally contributed the most to the Bx biosynthesis in hexaploid wheat, especially in shoots. In tetraploid wheat and the three diploid progenitors of hexaploid wheat, the respective transcript levels of the TaBx homoeologs were similar in ratio to those observed in hexaploid wheat. This result indicates that the genomic bias in the transcription of the TaBx genes in hexaploid wheat originated in the diploid progenitors and has been retained through the polyploidization.

Base Sequence↗
PubMed2006

Gene evolution at the ends of wheat chromosomes.

Wheat ESTs mapped to deletion bins in the distal 42% of the long arm of chromosome 4B (4BL) were ordered in silico based on blastn homology against rice pseudochromosome 3. The ESTs spanned 29 cM on the short arm of rice chromosome 3, which is known to be syntenic to long arms of group-4 chromosomes of wheat. Fine-scale deletion-bin and genetic mapping revealed that 83% of ESTs were syntenic between wheat and rice, a far higher level of synteny than previously reported, and 6% were nonsyntenic (not located on rice chromosome 3). One inversion spanning a 5-cM region in rice and three deletion bins in wheat was identified. The remaining 11% of wheat ESTs showed no sequence homology in rice and mapped to the terminal 5% of the wheat chromosome 4BL. In this region, 27% of ESTs were duplicated, and it accounted for 70% of the recombination in the 4BL arm. Globally in wheat, no sequence homology ESTs mapped to the terminal bins, and ESTs rarely mapped to interstitial chromosomal regions known to be recombination hot spots. The wheat-rice comparative genomics analysis indicated that gene evolution occurs preferentially at the ends of chromosomes, driven by duplication and divergence associated with high rates of recombination.

Chromosome Mapping↗