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PubMed2004

Degradation of wheat allergen in Japanese soy sauce.

Soy sauce is a traditional fermented seasoning of East Asian countries and is available throughout the world. Wheat and soybeans are the 2 main raw materials of soy sauce, and soy sauce also contains a high concentration of salt. Since wheat allergy is considered a serious problem globally, it is significant to examine the allergenicity of soy sauce. In this study, by immunoblotting, inhibition ELISA and direct ELISA using sera from 5 children with wheat allergy, it was clearly demonstrated that wheat allergens were degraded into amino acids and peptides losing the IgE-binding ability in both salt-soluble and salt-insoluble fractions of soy sauce during fermentation. Furthermore, no wheat allergen was detected in 10 items of commercial soy sauce in Japan, by inhibition ELISA or direct ELISA using the sera of patients. In the brewing process of soy sauce, first salt-insoluble wheat allergen was solubilized to salt water during the koji stage (mold cultivation and enzyme production), and second both the resultant salt-solubilized and initially salt-soluble wheat allergens were completely degraded during the moromi stage (fermentation) by microbial proteolytic enzymes. Therefore, it was concluded that no wheat allergen is contained in soy sauce.

Allergens↗
PubMed1993

Immobilization of Fc epsilon receptors by wheat germ agglutinin. Receptor dynamics in IgE-mediated signal transduction.

Transmembrane signaling initiated by the receptor with high affinity for Fc stem of IgE(Fc epsilon RI) requires the diffusion-dependent cross-linkage and persistent aggregation of the Fc epsilon RI. Disruption or prevention of receptor cross-links at any time during the secretory response quickly terminates secretion. We found that in the rat basophilic leukemia mast cell line, addition of wheat germ agglutinin, a lectin that binds to the Fc epsilon RI alpha subunit, caused a precipitous decline in the lateral diffusional and electrokinetic mobilities of the Fc epsilon RI. Both the unoccupied Fc epsilon RI and IgE-Fc epsilon RI complexes became immobilized, as determined from in situ electromigration and postelectric field relaxation. Immobilization of the Fc epsilon RI by wheat germ agglutinin was accompanied by a ligand-reversible association of 125I-IgE-Fc epsilon RI complexes with the Triton X-100-insoluble cytoskeletal fraction. Wheat germ agglutinin rapidly inhibited Fc epsilon RI-mediated signal transduction and secretion, whether cross-linkage was initiated by multivalent antigen, covalent IgE oligomers, anti-IgE, or anti-Fc epsilon RI antibody. Inhibition of signaling and secretion occurred on simultaneous addition of wheat germ agglutinin and antigen, and also when wheat germ agglutinin was added at increasing times after induction of Fc epsilon RI cross-linkage. Wheat germ agglutinin neither reduced the affinity of anti-DNP IgE for haptenic DNP-lysine nor reversed the binding of IgE to the Fc epsilon RI. Although wheat germ agglutinin caused internalization of the Fc epsilon RI, the onset of inhibition preceded and its extent exceeded that of internalization. Wheat germ agglutinin did not interfere with the secretory apparatus, as indicated by its lack of inhibition of secretion elicited by calcium ionophores. These findings suggest that inhibition of signal transduction is secondary to an initial event linked to immobilization of the Fc epsilon RI. Implications of these results are discussed with respect to the dynamics of Fc epsilon RI aggregation on rat basophilic leukemia cells.

Animals↗
PubMed2005

A laboratory-based comparison of a molluscicide and an alternative food source (red clover) as means of reducing slug damage to winter wheat.

Slugs are major pests of many crops in the UK, including winter wheat, yet current methods of control are often unreliable. This study investigates the potential use of red clover, as an alternative food source, to reduce the amount of damage caused to winter wheat by the field slug, Deroceras reticulatum (Müller). Two laboratory-based studies, each conducted over a 7-day period, investigated the effects of red clover seedlings and commercial metaldehyde pellets on damage to winter wheat seeds and seedlings. The results indicate that metaldehyde applications, in the form of commercially available pellets, resulted in significantly greater protection to wheat seeds compared with red clover, whereas metaldehyde and red clover were equally as effective in reducing damage to wheat seedlings. A further laboratory experiment investigated the effect of two slug population densities (48 and 16 adults m(-2)) and high and low red clover seed rates (125% and 75% of a standard rate) on damage to wheat seeds. Results showed that, at the highest slug population density, red clover sown at 125% of the standard rate gave 99% protection to wheat seeds, compared with the 75% seed rate which gave 55%. At the lower slug population density, both seed rates of red clover resulted in similar levels of protection. Implications for the potential use of red clover as an alternative food source for reducing damage to winter wheat in field conditions are discussed.

Acetaldehyde↗
PubMed2001

Effects of oat and wheat cereals on endothelial responses.

BACKGROUND: This study was undertaken to determine the effects of month-long whole grain oat and wheat cereal supplementation on endothelial function following a fatty meal as measured by brachial artery reactivity studies. METHODS: Fifty healthy adult subjects underwent brachial artery reactivity studies before and after a high-fat meal along with alpha-tocopherol (vitamin E), oats, or a comparable bowl of wheat cereal and were again tested after the high-fat meal following month-long supplementation with oat or wheat cereal in a random crossover with interim washout. RESULTS: In the acute phase, the fatty meal attenuated the hyperemic brachial artery flow response when administered concurrently with wheat cereal (-13.4%; P = 0.02), whereas hyperemic flow was maintained by concurrent administration of either oatmeal or alpha-tocopherol. Following month-long supplementation, postprandial peak flow (wheat +3.88 +/- 5.62%; oat -10.78 +/- 7.15%), and peak diameter (wheat -1.40 +/- 0.96%; oat -0.86 +/- 0.88%) did not differ from preprandial values. Oat and wheat treatments did not differ when directly compared. CONCLUSIONS: Month-long, daily supplementation with either whole-grain oat or wheat cereal may prevent postprandial impairment of vascular reactivity in response to a high-fat meal.

Adult↗
PubMed1993

Comparative analysis of a recombining-repeat-sequence family in the mitochondrial genomes of wheat (Triticum aestivum L.) and rye (Secale cereale L.).

The mitochondrial genomes of wheat and rye each contain a three-member family of recombining repeat sequences (the "18S/5S repeat") that encode genes for 18S and 5S rRNAs (rrn18 and rrn5) and tRNA(fMet) (trnfM). Here we present, for wheat and rye, the sequence and boundaries of the "common sequence unit" (CSU) that is shared between all three repeat copies in each species. The wheat CSU is 4,429 base-pairs long and contains (in addition to trnfM, rrn18 and rrn5) a putative promoter, three tRNA-like elements ("t-elements"), and part of a pseudogene ("psi atpAc") that is homologous to chloroplast atpA, which encodes the alpha subunit of chloroplast F1 ATPase. The rye CSU is somewhat smaller (2,855 base pairs) but contains much the same genic and other sequence elements as its wheat counterpart, except that two of the three t-elements as well as psi atpAc are found in only one of the three downstream flanks of the 18S/5S repeat, outside the CSU boundaries. In interpreting the sequence data in terms of the evolutionary history of the 18S/5S-repeat family of wheat and rye, we conclude that: (1) the wheat-rye form of the 18S/5S repeat most likely originated between 3 and 14 million years ago, in a lineage that gave rise to wheat and rye but not to barley, oats, rice or maize; (2) the close linkage (1-bp apart) between trnfM and rrn18 is similarly limited in its taxonomic distribution to the wheat/rye lineage; (3) the trnfM-rrn18 pair arose via a single mutation that inserted a sequence block containing trnfM immediately upstream of rrn18; and (4) the presence of a putative promoter upstream of rrn18 in all wheat and rye repeats is consistent with all three repeat copies being transcriptionally active. We discuss these conclusions in the light of the possible functional significance of recombining-repeats in plant mitochondrial genomes.

Base Sequence↗
PubMed1994

Introgression of Elymus trachycaulus chromatin into common wheat.

A number of wheat-Elymus trachycaulus (2n = 4x = 28, genomically StStHtHt) chromosome addition, substitution, and translocation lines were isolated from the derivatives of an E. trachycaulus x wheat hybrid. Eighteen out of a total of 28 chromosome arms of E. trachycaulus were recovered in the addition lines. The genomic affinity of individual E. trachycaulus chromosomes was analysed by comparative chromosome banding and in situ hybridization using genome-specific repetitive DNA sequences as probes. The homoeology of the E. trachycaulus chromosomes added to wheat was determined by storage protein, isozyme, and restriction fragment length polymorphism analysis. Alloplasmic wheat-E. trachycaulus chromosome additions were isolated which only involved chromosome 1Ht and 1St that carry fertility restoration gene Rf-Ht1 and Rf-St1, respectively. Based on the results of production and characterization of a wheat-E. trachycaulus 5Ht(5B) substitution line, it is likely that some wheat chromosomes can be well compensated genetically by E. trachycaulus chromosomes. Several spontaneous wheat-E. trachycaulus chromosome translocation lines were detected. All the translocation lines involved either 1Ht or 1St. To estimate the potential of recombination between wheat and E. trachycaulus chromosomes, a backcross population derived from a plant which was double monosomic for chromosomes 7A and 7AL.7AS-1StS and a ph1b gene was developed. The plants from this population were analysed for 1St-specific genetic markers and no recombinant was recovered.

Chromosome Banding↗
PubMed1996

Relationship between the levels of wheat-rye metaphase I chromosomal pairing and recombination revealed by GISH.

The metaphase I and anaphase I stages of meiosis of wheat x rye hybrids carrying the ph1b mutation were analyzed by genomic in situ hybridization. This technique allows distinction between three different types of wheat-rye associations in metaphase I configurations as well as detection of wheat-rye recombinant chromosomes in anaphase I cells. The frequency of associations between wheat and rye chromosomes greatly exceeded the level of wheat-rye recombination found in the three hybrids examined. Extremely distal associations, which account for about 50% of the total wheat-rye metaphase I chromosomal pairing, can explain such a discrepancy between metaphase I and anaphase I data. It is further discussed whether these associations reflect very distally located chiasmata or nonchiasmatic pairing. The sizes of the segments exchanged in wheat-rye recombinant chromosomes provide cytological evidence that wheat-rye recombination is restricted to the distal chromosomal regions.

Anaphase↗
PubMed2004

Genomic constitution and variation in five partial amphiploids of wheat--Thinopyrum intermedium as revealed by GISH, multicolor GISH and seed storage protein analysis.

Genomic in situ hybridization (GISH) and multicolor GISH (mcGISH) methodology were used to establish the cytogenetic constitution of five partial amphiploid lines obtained from wheat x Thinopyrum intermedium hybridizations. Line Zhong 1, 2 n=52, contained 14 chromosomes from each of the wheat genomes plus ten Th. intermedium chromosomes, with one pair of A-genome chromosomes having a Th. intermedium chromosomal segment translocated to the short arm. Line Zhong 2, 2 n=54, had intact ABD wheat genome chromosomes plus 12 Th. intermedium chromosomes. The multicolor GISH results, using different fluorochrome labeled Th. intermedium and the various diploid wheat genomic DNAs as probes, indicated that both Zhong 1 and Zhong 2 contained one pair of Th. intermedium chromosomes with a significant homology to the wheat D genome. High-molecular-weight (HMW) glutenin and gliadin analysis revealed that Zhong 1 and Zhong 2 had identical banding patterns that contained all of the wheat bands and a specific HMW band from Th. intermedium. Zhong 1 and Zhong 2 had good HMW subunits for wheat breeding. Zhong 3 and Zhong 5, both 2 n=56, possessed no gross chromosomal aberrations or translocations that were detectable at the GISH level. Zhong 4 also had a chromosome number of 2 n=56 and contained the complete wheat ABD-genome chromosomes plus 14 Th. intermedium chromosomes, with one pair of Th. intermedium chromosomes being markedly smaller. Multicolor GISH results indicated that Zhong 4 also contained two pairs of reciprocally translocated chromosomes involving the A and D genomes. Zhong 3, Zhong 4 and Zhong 5 contained a specific gliadin band from Th. intermedium. Based on the above data, it was concluded that inter-genomic transfer of chromosomal segments and/or sequence introgression had occurred in these newly synthesized partial amphiploids despite their diploid-like meiotic behavior and disomic inheritance.

Breeding↗
PubMed2004

Genome-specific primer sets for starch biosynthesis genes in wheat.

Common wheat (Triticum aestivum L.,2n=6x=42) is an allohexaploid composed of three closely related genomes, designated A, B, and D. Genetic analysis in wheat is complicated, as most genes are present in triplicated sets located in the same chromosomal regions of homoeologous chromosomes. The goal of this report was to use genomic information gathered from wheat-rice sequence comparison to develop genome-specific primer sets for five genes involved in starch biosynthesis. Intron locations in wheat were inferred through the alignment of wheat cDNA sequences with rice genomic sequence.Exon-anchored primers, which amplify across introns,allowed the sequencing of introns from the three genomes for each gene. Sequence variation within introns among the three wheat genomes provided the basis for genome-specific primer design. For three genes, ADP-glucose pyrophosphorylase (Agp-L), sucrose transporter (SUT),and waxy (Wx), genome-specific primer sets were developed for all three genomes. Genome-specific primers were developed for two of the three genomes for Agp-S and starch synthase I (Ssl). Thus, 13 of 15 possible genome-specific primer sets were developed using this strategy. Seven genome-specific primer combinations were used to amplify alleles in hexaploid wheat lines for sequence comparison. Three single nucleotide polymorphisms(SNPs) were identified in a comparison of 5,093 bp among a minimum of ten wheat accessions. Two of theseSNPs could be converted into cleaved amplified polymorphism sequence (CAPS) markers. Our results indicated that the design of genome-specific primer sets using intron-based sequence differences has a high probability of success, while the identification of polymorphism among alleles within a genome may be a challenge.

Base Sequence↗
PubMed2005

Wheat genetic diversity trends during domestication and breeding.

It has been claimed that plant breeding reduces genetic diversity in elite germplasm which could seriously jeopardize the continued ability to improve crops. The main objective of this study was to examine the loss of genetic diversity in spring bread wheat during (1) its domestication, (2) the change from traditional landrace cultivars (LCs) to modern breeding varieties, and (3) 50 years of international breeding. We studied 253 CIMMYT or CIMMYT-related modern wheat cultivars, LCs, and Triticum tauschii accessions, the D-genome donor of wheat, with 90 simple sequence repeat (SSR) markers dispersed across the wheat genome. A loss of genetic diversity was observed from T. tauschii to the LCs, and from the LCs to the elite breeding germplasm. Wheat's genetic diversity was narrowed from 1950 to 1989, but was enhanced from 1990 to 1997. Our results indicate that breeders averted the narrowing of the wheat germplasm base and subsequently increased the genetic diversity through the introgression of novel materials. The LCs and T. tauschii contain numerous unique alleles that were absent in modern spring bread wheat cultivars. Consequently, both the LCs and T. tauschii represent useful sources for broadening the genetic base of elite wheat breeding germplasm.

Breeding↗
PubMed2005

Mapping a resistance gene in wheat cultivar Yangfu 9311 to yellow mosaic virus, using microsatellite markers.

Wheat yellow mosaic disease, which is caused by wheat yellow mosaic bymovirus (WYMV) and transmitted by soil-borne fungus, results in severe damage on wheat (Triticum aestivum L.) production in China. For development of resistant cultivars to reduce wheat yield losses due to wheat yellow mosaic disease, resistance test and genetic analysis indicated that a single dominant gene in wheat cultivar Yangfu 9311 contributed to the resistance. Bulk segregant analysis was used to identify microsatellite markers linked to the resistance gene in an F(2) population derived from the cross Yangfu 9311 (resistant) x Yangmai 10 (susceptible). Microsatellite markers Xwmc41, Xwmc181, Xpsp3039, and Xgwm349 were co-dominantly or dominantly linked with the gene responsible for WYMV resistance at a distance of 8.1-11.6 cM. Based on the wheat microsatellite consensus map and the results from amplification of the cultivar Chinese Spring nulli-tetrasomic stocks, the resistance gene to wheat yellow mosaic disease derived from Yangfu 9311, temporarily named as YmYF, was thus mapped on the long arm of chromosome 2D (2DL).

China↗
PubMed2005

High transferability of bread wheat EST-derived SSRs to other cereals.

The increasing availability of expressed sequence tags (ESTs) in wheat (Triticum aestivum) and related cereals provides a valuable resource of non-anonymous DNA molecular markers. In this study, 300 primer pairs were designed from 265 wheat ESTs that contain microsatellites in order to develop new markers for wheat. Their level of transferability in eight related species [Triticum durum, T. monococcum, Aegilops speltoides, Ae. tauschii, rye (Secale cereale), barley (Hordeum vulgare), Agropyron elongatum and rice (Oryza sativa)] was assessed. In total, 240 primer pairs (80%) gave an amplification product on wheat, and 177 were assigned to wheat chromosomes using aneuploid lines. Transferability to closely related Triticeae species ranged from 76.7% for Ae. tauschii to 90.4% for T. durum and was lower for more distant relatives such as barley (50.4%) or rice (28.3%). No clear putative function could be assigned to the genes from which the simple sequence repeats (SSRs) were developed, even though most of them were located inside ORFs. BLAST: analysis of the EST sequences against the 12 rice pseudo-molecules showed that the EST-SSRs are mainly located in the telomeric regions and that the wheat ESTs have the highest similarity to genes on rice chromosomes 2, 3 and 5. Interestingly, most of the SSRs giving an amplification product on barley or rice had a repeated motif similar to the one found in wheat, suggesting a common ancestral origin. Our results indicate that wheat EST-SSRs show a high level of transferability across distantly related species, thereby providing additional markers for comparative mapping and for following gene introgressions from wild species and carrying out evolutionary studies.

Chromosome Mapping↗
PubMed2006

Impact of plant breeding on genetic diversity of the Canadian hard red spring wheat germplasm as revealed by EST-derived SSR markers.

Genetic diversity changes in wheat germplasm have been studied using different molecular markers, but little is known about the impact of plant breeding on the transcribed segments of the wheat genome. The objective of this study was to assess diversity changes in 75 Canadian hard red wheat cultivars released from 1845 to 2004 using 37 EST-derived microsatellite (eSSR) markers. These markers were derived from at least 19 transcribed sequences with putative functions assigned and sampled 17 wheat chromosomes. A total of 138 eSSR alleles was detected, and their allelic frequencies ranged from 0.01 to 0.99 with an average of 0.41. Allelic counts were significantly reduced at three loci for cultivars released after 1990. Sixteen alleles at 14 loci in pre-1910 cultivars were lost in cultivars released after 1990. The lost alleles had frequencies ranging from 0.03 to 0.17 and averaging 0.07. Partitioning the eSSR variation showed the four ancestral families accounted for 14.7% of the variation, followed by the six breeding periods with 12.8% and the eight breeding programs with 5.8%. A genetic shift was observed in the cultivars released over the six breeding periods, reflecting the various breeding efforts. These results illustrate the impact of the Canadian wheat breeding on the transcriptional segments of the wheat genome. These findings, along with those from genomic SSR markers, suggest the Canadian wheat breeding programs have reduced genetic diversity in the hard red spring wheat.

Alleles↗
PubMed2003

Pistillody is caused by alterations to the class-B MADS-box gene expression pattern in alloplasmic wheats.

Class-B floral homeotic genes are involved in specifying petal and stamen identity during flower development in plant species. Homeotic transformation of stamens into pistil-like structures (called pistillody) has been observed in alloplasmic lines of bread wheat ( Triticum aestivum L.) having the cytoplasm of a wild relative species, Aegilops crassa Boiss. To obtain information about the molecular mechanism underlying pistillody induction, we isolated two PISTILLATA ( PI)-type class-B MADS-box genes, WPI1 ( wheat PI STILLATA # 1) and WPI2, from wheat. Phylogenetic reconstruction indicated that WPI1 is orthologous to OsMADS4 and that WPI2 is probably an ortholog of OsMADS2. Both OsMADS4 and OsMADS2 genes were suggested to be PI orthologs in rice, and the function of OsMADS4 as a class-B gene was proven by the transgenic study. An in situ hybridization study demonstrated that the WPI1 gene is expressed in primordia of lodicules and stamens in developing florets in wheat. In the alloplasmic wheat line exhibiting pistillody, the WPI1 transcripts were not detected in the primordia of pistil-like stamens, whereas WPI1 was expressed in the lodicules. The wheat APETALA3 ( AP3)-type class-B MADS-box gene WAP3 ( wheat AP3) /TaMADS#82 showed an expression pattern similar to that of WPI1. These results suggest that pistillody in alloplasmic wheats is caused by alterations to the expression pattern of class-B MADS-box genes.

Amino Acid Sequence↗
PubMed2006

Performance of wheat crops with different chromosome ploidy: root-sourced signals, drought tolerance, and yield performance.

Pot-culture experiments were carried out to estimate the role of non-hydraulic root signals (nHRS) and the relation of these signals to drought tolerance and grain yield formation under drought stress in six wheat varieties. These were two modern hexaploid wheat (Triticum aestivum L., AABBDD) Plateau602 and Longchun8139-2, two diploid wheat (Triticum monococcum L., AB) MO1 and MO4, and two tetraploid wheat (Triticum dicoccum Schuebl L., AABB) DM22 and DM31. In the two diploid relatives, the nHRS was switched on and off at a soil water content (SWC) of approximately 53-45% field water capacity (FWC). In contrast, in the modern hexaploid varieties, Longchun8139-2 and Plateau602 the nHRS occurred between a SWC of about 71 and 35% FWC, a much wider soil moisture range. The two tetraploid relatives, DM22 and DM31, were generally intermediate. The nHRS threshold range in SWC also narrowed as all six varieties went through successive developmental stages from shooting to grain filling. The two hexaploid wheat varieties had the longest duration of survival after the water supply ceased, and the best yield stability under drought stress, similar to with tetraploid wheat varieties; the diploid wheat varieties were least robust. These two parameters were both significantly correlated with the nHRS soil moisture threshold range (r=0.9456** and 0.8608*, respectively). Based on these patterns, we propose a "triple Z" model to describe the features of non-hydraulic stomatal sensitivity versus soil drought in wheat growth.

Crops, Agricultural↗
PubMed2005

Large deletions within the first intron in VRN-1 are associated with spring growth habit in barley and wheat.

The broad adaptability of wheat and barley is in part attributable to their flexible growth habit, in that spring forms have recurrently evolved from the ancestral winter growth habit. In diploid wheat and barley growth habit is determined by allelic variation at the VRN-1 and/or VRN-2 loci, whereas in the polyploid wheat species it is determined primarily by allelic variation at VRN-1. Dominant Vrn-A1 alleles for spring growth habit are frequently associated with mutations in the promoter region in diploid wheat and in the A genome of common wheat. However, several dominant Vrn-A1, Vrn-B1, Vrn-D1 (common wheat) and Vrn-H1 (barley) alleles show no polymorphisms in the promoter region relative to their respective recessive alleles. In this study, we sequenced the complete VRN-1 gene from these accessions and found that all of them have large deletions within the first intron, which overlap in a 4-kb region. Furthermore, a 2.8-kb segment within the 4-kb region showed high sequence conservation among the different recessive alleles. PCR markers for these deletions showed that similar deletions were present in all the accessions with known Vrn-B1 and Vrn-D1 alleles, and in 51 hexaploid spring wheat accessions previously shown to have no polymorphisms in the VRN-A1 promoter region. Twenty-four tetraploid wheat accessions had a similar deletion in VRN-A1 intron 1. We hypothesize that the 2.8-kb conserved region includes regulatory elements important for the vernalization requirement. Epistatic interactions between VRN-H2 and the VRN-H1 allele with the intron 1 deletion suggest that the deleted region may include a recognition site for the flowering repression mediated by the product of the VRN-H2 gene of barley.

Alleles↗
PubMed2005

Updating of transposable element annotations from large wheat genomic sequences reveals diverse activities and gene associations.

Triticeae species (including wheat, barley and rye) have huge and complex genomes due to polyploidization and a high content of transposable elements (TEs). TEs are known to play a major role in the structure and evolutionary dynamics of Triticeae genomes. During the last 5 years, substantial stretches of contiguous genomic sequence from various species of Triticeae have been generated, making it necessary to update and standardize TE annotations and nomenclature. In this study we propose standard procedures for these tasks, based on structure, nucleic acid and protein sequence homologies. We report statistical analyses of TE composition and distribution in large blocks of genomic sequences from wheat and barley. Altogether, 3.8 Mb of wheat sequence available in the databases was analyzed or re-analyzed, and compared with 1.3 Mb of re-annotated genomic sequences from barley. The wheat sequences were relatively gene-rich (one gene per 23.9 kb), although wheat gene-derived sequences represented only 7.8% (159 elements) of the total, while the remainder mainly comprised coding sequences found in TEs (54.7%, 751 elements). Class I elements [mainly long terminal repeat (LTR) retrotransposons] accounted for the major proportion of TEs, in terms of sequence length as well as element number (83.6% and 498, respectively). In addition, we show that the gene-rich sequences of wheat genome A seem to have a higher TE content than those of genomes B and D, or of barley gene-rich sequences. Moreover, among the various TE groups, MITEs were most often associated with genes: 43.1% of MITEs fell into this category. Finally, the TRIM and copia elements were shown to be the most active TEs in the wheat genome. The implications of these results for the evolution of diploid and polyploid wheat species are discussed.

DNA Transposable Elements↗
PubMed2004

Microcolinearity between a 2-cM region encompassing the grain protein content locus Gpc-6B1 on wheat chromosome 6B and a 350-kb region on rice chromosome 2.

The conservation of the linear order (colinearity) of genetic markers along large chromosome segments in wheat and rice is well established, but less is known about the microcolinearity between both genomes at subcentimorgan distances. In this study we focused on the microcolinearity between a 2.6-cM interval flanked by markers Xcdo365 and Xucw65 on wheat chromosome 6B and rice chromosome 2. A previous study has shown that this wheat segment includes the Gpc-6B1 locus, which is responsible for large differences in grain protein content (GPC) and is the target of a positional cloning effort in our laboratories. Twenty-one recombination events between Xcdo365 and Xucw65 were found in a large segregating population (935 gametes) and used to map 17 genes selected from rice chromosome 2 in the wheat genetic map. We found a high level of colinearity between a 2.1-cM region flanked by loci Xucw75 and Xucw67 on wheat chromosome 6B and a 350-kb uninterrupted sequenced region in rice chromosome arm 2S. Colinearity between these two genomes was extended to the region proximal to Xucw67 (eight colinear RFLP markers), but was interrupted distal to Xucw75 (six non-colinear RFLP markers). Analysis of different comparative studies between rice and wheat suggests that microcolinearity is more frequently disrupted in the distal region of the wheat chromosomes. Fortunately, the region encompassing the Gpc-6B1 locus showed an excellent conservation between the two genomes, facilitating the saturation of the target region of the wheat genetic map with molecular markers. These markers were used to map the Gpc-6B1 locus into a 0.3-cM interval flanked by PCR markers Xucw79 and Xucw71, and to identify five candidate genes within the colinear 64-kb region in rice.

Chromosomes, Plant↗