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Transfer of rye chromosome segments to wheat by a gametocidal system.

A gametocidal chromosome derived from Aegilops triuncialis (3C) induces chromosome mutations in gametes lacking the 3C chromosome in common wheat (Triticum aestivum L.). We combined 3C with chromosome 1R of rye (Secale cereale L.) in a common wheat line to know how efficiently 3C induces transfers of small 1R segments to wheat. In the 811 progeny of this wheat line, we found five wheat chromosomes (2A, 2D, 3D, 5D and 7D) carrying segments of the 1R satellite. Wheat plants carrying these translocations were tested for the presence of a storage protein locus Sec-1 and a cluster of resistance genes for wheat rust diseases, Sr31, Lr26 and Yr9. The 2A and 2D translocations had the Sec-1 and three rust resistance loci. The 3D and 5D translocations had Sr31, Lr26 and Yr9 but not Sec-1. The 7D translocation lacked Sec-1, Lr26 and Yr9, but the presence of Sr31 in this translocation was not determined. This showed that the translocation points fell into three regions of the 1R satellite, namely, proximal to Sec-1, between Sec-1 and the rust resistance loci, and distal to the rust resistance loci. Thus, the 3C gametocidal system was demonstrated to be effective in transferring small rye chromosome segments.

Chromosomes↗

[Sequence analysis of alpha-amylase inhibitors genes with resistance to insects in wheat and Aegilops].

The alpha-amylase inhibitors have been proposed as possibly important weapons against pests. Thus, it is of importance to identify the specificity of them. Based on the EST data of alpha-amylase inhibitor genes that were retrieved from NCBI, BBSRC and GrainGenes, two PCR primers were designed. The coding sequences of 24 kD dimeric alpha-amylase inhibitors with resistance to insects in 17 wheat and Aegilops accessions were investigated and 17 new genes were obtained. Only one 24 kD alpha-amylase inhibitor gene was found in each diploid wheat and Aegilops accession, whereas 8 genes were characterized from one hexaploid wheat variety, indicating that the 24 kD alpha-amylase inhibitors in hexaploid wheat were encoded by multi-gene. The deduced amino acid sequences of 2 genes from common wheat and 1 gene from Ae. tauschii were the same as the sequence of the inhibitor 0.19, and the deduced amino acid sequence of another gene from common wheat was similar to the inhibitor 0.53 with only one amino acid difference. The amino acid sequences of 24 kD dimeric alpha-amylase inhibitors shared very high coherence (91.2%). These results suggest that the alpha-amylase inhibitors in 24 kD family were derived from common ancestral genes by phylogenesis.

Amino Acid Sequence↗

[Fluorescence in situ hybridization applied to the meiotic analysis and spontaneous chromosome translocation in the pollen mother cells of hybrids of Triticum-Haynaldia].

Fluorescence in situ hybridization was applied to the meiotic analysis and chromosome pairing in the pollen mother cells of hybrids of Triticum-Haynaldia. The results indicated that most (90.5%-93.2%) of the PMCs of two Triticum-Haynaldia hybrids contained two univalents involving one Haynaldia chromosome at metaphase I, and only 1 of 320 PMCs with homologous pairing between one wheat chromosome and one Haynaldia chromosome was observed in the hybrid of Guinong 22 x common wheat Chinese Spring, the frequency was 0.3%. The frequencies of the PMCs with mis-dividing chromosome ranged from 32.7% to 37.5% at anaphase I and from 20.5% to 24.4% at anaphase II in the hybrids between Triticum-Haynaldia. The frequency of Haynaldia chromatin translocating into Triticum chromosome was about 0.7% at anaphase I in the hybrid of Guinong 22 x common wheat Chinese Spring and was 0.8%-1.7% at anaphase II in two wheat-Haynaldia hybrids. Otherwise, the chromosome morphology involving Haynaldia chromatin was observed at preleptotene I, and the frequencies of chromatin nucleus at tetrad stage and at microspore stage were investigated. The time of chromosome translocation in meiosis and the transmitting frequencies of Haynaldia chromosome in wheat background were discussed.

Gene Frequency↗

[Expression of fertility during morphogenesis in self-pollinated backcrossed progenies of barley-wheat amphiploids].

The fertility characteristics expressed during morphogenesis in first-generation self-pollinated backcrossed progenies (BC1) obtained from amphiploid barley-wheat hybrids [Hordeum geniculatum All. (2n = 28) x Triticum aestivum L. (2n = 42)] (2n = 70) backcrossed with common wheat were studied. It was found that, in the case of self-pollination of BC1 plants, karyotype stabilization leads to the formation of alloplasmic euploid (2n = 42), telocentric substitution (2n = 40 + 2t), and telocentric addition (2n = 42 + 2t), (2n = 42 + 2t) plant forms, which may serve as the sources of the respective alloplasmic lines of common wheat. That the expression of fertility characters in BC1F8 plants was shown to depend on growth conditions. The main mechanism of hybrid incompatibility of BC1F1-BC1F8 plants was expressed as grass-clump dwarfism.

Chimera↗

[Identification of blue grained wheat and its irradiation-mutated offsprings by genomic in situ hybridization (GISH)].

Transferring useful chromosome(s), chromosomal fragment(s) or genes from related species into common wheat (Triticum aestivum L.) is an effective method for improving wheat cultivars, and DNA:DNA in situ hybridization has been proven to be an effective method for directly demonstrating alien chromosome number and distribution in plant. In this study, genomic in situ hybridization (GISH) was used to identify the chromosomal constitutions of the blue-grained wheat Blue-58 originated from distant hybridization between Triticum aestivum L. and Agropyron elongatum (Host) Beauv (2n = 10x = 70) and its irradiation-mutated offsprings. The results showed that, as previously reported, Blue-58 (2n = 42) was a substitution line in which a pair of 4D chromosomes of common wheat was substituted by a pair of 4E chromosomes from Agropyron elongatum. Mutation line LW004 might be a homozygous reciprocal translocation line in which two pair of chromosomes might be involved in the translocation event and it showed high efficiency in utilizing soil phosphorus in our field screening experiments. Mutation line LW43-3-4 was a blue monosomic line with 40 wheat chromosomes plus one 4E chromosome from Agropyron elongatum in its genome and its seeds showed light-blue color. Some other chromosome rearrangements and structure changes were also detected among the mutated offsprings through GISH, such as telomonosomic line (40 W + 1't4E) and a line with a chromosomal constitution of 39 W + 1'4E + 1't4E. Our results indicated very clearly that it was the chromosome derived from Agropyron elongatum carried gene(s) responsible for the blue pigmentation in wheat grains and it was also illustrated from our results that the combination of effective methods for generating mutations at chromosomal level and convenient detection of these mutations played pivotal roles in creating materials for chromosome engineering and in breeding by means of chromosome engineering.

In Situ Hybridization↗

Screening and applying wheat microsatellite markers to trace individual Haynaldia villosa chromosomes.

Wheat (Triticum aestivum L.) microsatellite markers were screened for detecting Haynaldia villosa L. chromosomes introduced into wheat background. Two hundred and seventy six primer pairs mapped on 7 homeologous groups of wheat were used to amplify the gDNA of T. aestivum and H. villosa. The results showed that 148 of 276 microsatellite primers amplified polymorphic bands between common wheat cv. Chinese Spring and H. villosa. Primers wmc49 (1BS), wmc25 (2BS), gdm36 (3DS), gdm145 (4AL), wmc233 (5DS), wmc256 (6AL) and gwm344 (7BL) produced a specific polymorphic DNA fragment on chromosome 1V to 7V of H. villosa, respectively. In addition, gwm469 (6DS) detected a specific band on 2V; gdm107 (2DS) amplified a specific band on 6V. These microsatellite markers were effective in identifying individual H. villosa chromosomes in other T. aestivum-H. villosa chromosome addition, substitution and translocation lines involved in different H. villosa accessions and wheat backgrounds. Therefore, these chromosome-specific microsatellite markers could be used as molecular markers for detection of chromosomes of H. villosa in common wheat.

Agropyron↗

[Analysis of isogenic lines of the soft wheat carrying dominant alleles of Bg, Hg, and Rg1 genes using microsatellite and protein markers].

To determine tight linkage between morphological and molecular markers of the first homologous group of chromosomes of common wheat, microsatellite analysis of six near-isogenic lines with marker dominant alleles controlling back color (Bg; 1AS) and hairy glume (Hg; 1AS) and two lines bearing the dominant alleles of the gene for red glume color (Rgl; 1BS) was conducted. The component composition of gliadins in these lines was studied. Tight linkage of Bg, Hg, and Gli-A1 genes with a microsatellite marker Xgwm136 (1AS) and of Rg1 and Gli-B1 genes with markers Xgwm33 and Xgwm550 (1BS) was shown. Based on the results obtained and literature data, the most probable order of morphological and molecular markers on chromosomes of common wheat was determined. On chromosome 1AS, from the centromere to the telomere, the markers are located as follows: Xgwm136-Gli-A1-BgHg; on chromosome 1BS, in the same direction: Xgwm33-Gli-B1-Rg1-Xgwm550.

Chromosome Mapping↗

[Molecular analysis of the triticale lines with different Vrn gene systems using microsatellite markers and hybridization in situ].

Hexaploid triticale (x Triticosecale Wittmack) lines were examined using molecular markers and the hybridization in situ technique. Triticale lines were generated based on wheat varieties differing by the Vrn gene systems and the earing times. Molecular analysis was performed using Xgwm and Xrms microsatellite markers with the known chromosomal localization in the common wheat Triticum aestivum, and rye Secale cereale genomes. Comparative molecular analysis of triticale lines and their parental forms showed that all lines contained A and B genomes of common wheat and also rye homeologous chromosomes. In the three lines the presence of D genome markers, mapped to the chromosomes 2D and 7D, was demonstrated. This was probably the consequence of the translocations of homeologous chromosomes from wheat genomes, which took part during the process of triticale formation. The data obtained by use of genomic in situ hybridization supported the data of molecular genetic analysis. In none of the lines wheat--rye translocations or recombinations were observed. These findings suggest that the change of the period between the seedling appearance and earing time in triticale lines compared to the initial wheat lines, resulted from the inhibitory effect of rye genome on wheat vernalization genes.

Chromosomes, Plant↗

Identification, characterization, and comparison of RNA-degrading enzymes of wheat and barley.

RNA-degrading enzymes play an important role in regulating gene expression, and sequence analyses have revealed significant homology among several plant RNA-degrading enzymes. In this study we surveyed crude extracts of the above-ground part of the common wheat (Triticum aestivum L.) and the cultivated barley (Hordeum vulgare L.) for major RNA-degrading enzymes using a substrate-based SDS-PAGE assay. Fifteen wheat and fourteen barley RNA-degrading enzymes, with apparent molecular masses ranging from 16.3 to 40.1 kD, were identified. These RNA-degrading enzymes were characterized by their response to pH changes and addition of EDTA and ZnCl2 to the preincubation or incubation buffers. The 33.2- to 40.1-kD wheat and barley, 31.7-kD wheat, and 32.0-kD barley enzyme activities were inhibited by both zinc and EDTA and were relatively tolerant to alkaline environment. The 22.7- to 28.2-kD enzymes were inhibited by zinc but stimulated by EDTA. The 18.8-kD enzyme exists in both wheat and barley. It was active in an acid environment, was inhibited by zinc, but was not affected by EDTA. Two enzyme activities (31.0 and 32.0 kD) are unique to the common wheat.

Chlorides↗

Giemsa C-banding and the evolution of wheat.

The somatic chromosomes of common wheat, Triticum aestivum L. (2n = 6x = 42), and those of two of its diploid progenitors and T. speltoides, have been individually identified by a Giemsa staining technique. In wheat, telocentric chromosomes were used to aid the recognition of individual chromosomes, and an ideogram has been constructed depicting the C-band positions. There is no similarity in the C-banding of chromosomes within a homoeologous group, with the possible exception of group 5. Comparisons of the C-banding of the diploid species T. monococcum, T. speltoides, and T. tauschii with that of the A, B, and D genomes, respectively, in hexaploid wheat corroborate that T. speltoides could not be the donor of the B genome to wheat and that T. monococcum and T. tauschii are the probable donors of the A and D genomes, respectively.

Journal Article↗

Origin, dispersal and genomic structure of a low-copy-number hypervariable RFLP clone in Triticum and Aegilops species.

The genome of common wheat has evolved through allopolyploidization of three ancestral diploid genomes. A previously identified restriction fragment length polymorphism (RFLP) marker, pTag546, has the unique feature of showing hypervariability among closely related common wheat cultivars. To understand the origin and the mode of dispersal of this hypervariable sequence in the wheat genome, the distribution and structure of the homologous sequences were studied using ancestral diploid species, tetraploid disomic substitution lines and synthetic hexaploid lines. Comparative Southern blot and PCR analyses suggested that pTag546 homologs in the tetraploid and hexaploid wheat were derived from the S genome of Aegilops speltoides. Some pTag546 homologs were found to have transposed to A and D genomes in polyploid wheat. Evidence of transposition and elimination in some synthetic hexaploid lines was also obtained by comparing their copy numbers with those in the parental lines. Southern blot analysis of a genomic clone using a contiguous subset of sequences as probes revealed a core region of hypervariability that coincided with the region containing pTag546. No obvious structural characteristics that could explain the hypervariability, however, were found around the pTag546 sequence, except for accumulation of small repetitive sequences at one border. It was concluded that pTag546 increased its copy number through yet unknown mechanism(s) of transposition to various chromosomal locations over the period of allopolyploid evolution and during the artificial genome manipulation in wheat.

Blotting, Southern↗

Two quality-associated HMW glutenin subunits in a somatic hybrid line between Triticum aestivum and Agropyron elongatum.

High-molecular-weight glutenin subunits (HMW-GSs) from hybrid line II-12 between wheat (Triticum aestivum L.) and Agropyron elongatum (Host) Nivski were characterized with SDS-PAGE. Out of these HMW-GSs, two subunits, h1Bx and h1By, had mobilities similar to the subunits 1Bx13 and 1By16 from common wheat 4072, which was used as control. Polyclonal antibodies (pAbs) of h1Bx and h1By were prepared, and Western blotting showed that the pAbs had strong affinities for h1Bx and h1By, separately. The specificity of h1Bx-pAb was further checked; it preferentially recognized subunits h1Bx and 1Bx13. HMW-GS gene coding sequences were amplified by genomic polymerase chain reaction from hybrid II-12. Two of the five amplicons, marked II2a and II31b, were sequenced. Their coding sequences are clustered to Glu-1Bx7 and Glu-1By9 of common wheat. Three discrepant regions in deduced amino acid sequences of II2a and 31b repeated one time more than Glu-1Bx7 and Glu-1By9. N-terminal sequences of h1Bx and h1By were determined, which were identical to the published sequences of 1Bx13 and 1By16 and in agreement with that deduced from II2a and II31b, respectively. These results indicated that the two novel genes separated from the hybrid wheat derived from the allelic variation of 1Bx7 and 1By9 of the parent wheat. There is an additional cysteine residue positioned at 271st amino acid of the mature peptide of II2a, which may be related to the high quality of the flour.

Agropyron↗

An alternative to radiation hybrid mapping for large-scale genome analysis in barley.

The presence of a monosomic gametocidal chromosome (GC) in a barley chromosome addition line of common wheat generates structural aberrations in the barley chromosome as well as in the wheat chromosomes of gametes lacking the GC. A collection of structurally aberrant barley chromosomes is analogous to a panel of radiation hybrid (RH) mapping and is valuable for high-throughput physical mapping. We developed 90 common wheat lines (GC lines) containing aberrant barley 7H chromosomes induced by a gametocidal chromosome, 2C. DNAs isolated from these GC lines provided a panel of 7H chromosomal fragments in a wheat genetic background, comparable with RH mapping panels in mammals. We used this 7H GC panel and the methodology for RH mapping to physically map PCR-based barley markers, SSRs and AFLPs, onto chromosome 7H, relying on polymorphism between the 7H chromosome and the wheat genome. We call this method GC mapping. This study describes a novel adaptation and combination of methods of inducing chromosomal rearrangements to produce physical maps of markers. The advantages of the presented method are similar to RH mapping in that non-polymorphic markers can be used and the mapping panels can be relatively easily obtained. In addition, mapping results are cumulative when using the same mapping set with new markers. The GC lines will be available from the National Bioresources Project-KOMUGI ( http://www.nbrp.jp/index.jsp ).

Chromosomes, Plant↗

[The effect of rye chromosomes on callus induction and regeneration in callus cultures of immature embryos of wheat-rye substitution lines, Triticum aestivum L. cultivar Saratovskaia 29/Secale cereale L. cultivar Onokhoiskaia].

The effect of individual rye chromosomes on the induction of callus and the character of its regenerating capacity was studied with cultured immature embryos of wheat-rye (Triticum aestivum L. cv. Saratovskaya 29-Secale cereale L. cv. Onokhoiskaya) substitution lines. The genotypic diversity of the substitution lines proved to significantly affect variation of parameters characterizing the major types of callus cultures, that is, frequencies of embryogenic calli, which are capable of shoot regeneration, and of morphogenic calli, which produce root structures. Functioning in the genotypic background of common wheat cultivar Saratovskaya, chromosomes 2R and 3R of rye cultivar Onokhoiskaya stimulated significantly the induction of embryogenic callus highly capable of shoot regeneration. Rye chromosome 2R present in place of chromosome 2D in the common wheat genome suppressed the induction of callus producing root structures. Rye chromosomes 1R and 6R suppressed the induction of embryogenic callus capable of shoot regeneration.

Chromosomes, Plant↗

[Structural changes of 4V chromosome of Haynaldia villosa induced by gametocidal chromosome 3C of Aegilops triuncialis].

Chromosome 3C of Aegilops triuncialis was discovered with ability to be transferred preferentially in the case of its monosomic status in wheat background, whereas, those gametes without 3C would result in chromosome structural changes including deletions and translocations. In the present study, Triticum aestivum-Haynaldia villosa substitution line 4V(4D) developed in our laboratory, was crossed to T. aestivum c.v. Norin 26-Aegilops triuncialis 3C addition line, and the hybrids F1 were then backcrossed with common wheat in order to induce structural changes of 4V. Both chromosome C-banding and genomic in situ hybridization was applied to search such chromosome variations. In this case, total genomic DNA of Haynaldia villosa was labelled by Biotin-11-dUTP as probes and total genomic DNA of Chinese Spring as the block. Moreover, several chromosome changes within common wheat such as isochromosome 1BL.1BL(B39-2) and others were also revealed. The result indicated that two translocation lines T4VL.3AS(A47-10-3) and T4VS.4DL(A47-25-4), two telocentric chromosome lines A47-7-2(4VS) and A47-32-2(4VL), and two isochromosomes including 4VS.4VS(A47-23) and 4VL.4VL(A412-5-4) were identified from BC1F2 or BC1F3. This result indicated that gametocidal chromosome 3C of Aegilop triuncialis could effectively induce structural changes of both chromosome 4V of Haynaldia villosa and chromosomes of wheat.

Chromosome Aberrations↗

Multiplex PCR identification of wheat HMW glutenin subunit genes by allele-specific markers.

Wheat bread-making quality is closely correlated with composition and quantity of gluten proteins, in particular with high-molecular weight (HMW) glutenin subunits encoded by the Glu-1 genes. A multiplex polymerase chain reaction (PCR) method was developed to identify the allele composition of HMW glutenin complex Glu-1 loci (Glu-A1, Glu-B1 and Glu-D1) in common wheat genotypes. The study of multiplex PCR to obtain a well-balanced set of amplicons involved examination of various combinations of selected primer sets and/or thermal cycling conditions. One to three simultaneously amplified DNA fragments of HMW glutenin Glu-1 genes were separated by agarose slab-gel electrophoresis and differences between Ax1, Ax2* and Axnull genes of Glu-A1 loci, Bx6, Bx7 and Bx17 of Glu-B1, and Dx2, Dx5 and Dy10 genes of Glu-D1 loci were revealed. A complete agreement was found in identification of HMW glutenin subunits by both multiplex PCR analysis and SDS-PAGE for seventy-six Polish cultivars/strains of both spring and winter common wheat. Rapid identification of molecular markers of Glu-1 alleles by multiplex PCR can be an efficient alternative to the standard separation procedure for early selection of useful wheat genotypes with good bread-making quality.

Alleles↗

Copper toxicity thresholds for important restoration grass species of the Western United States.

Copper toxicity thresholds for plant species that are used in restoration activities in western North America have not been established. As a result, ecological risk assessments must rely on toxicity thresholds established for agronomic species, which usually differ from those of species used in restoration. Thus, risk assessors have the potential for classifying sites as phytotoxic to perennial, nonagronomic species and calling for intensive remediation activities that may not be necessary. The objective of this study was to provide a better estimate of Cu toxicity thresholds for five grass species that are commonly used in restoration efforts in the western United States. We used a greenhouse screening study where seedlings of introduced redtop (Agrostis gigantea Roth.), the native species slender wheatgrass (Elymus trachycaulus [Link] Gould ex Shinners var. Pryor), tufted hairgrass (Deschampsia caespitosa [L.] Beauvois), big bluegrass (Poa secunda J. Presl var. Sherman), and basin wildrye (Leymus cinereus [Scribner & Merrill] A. Love var. Magnar) and the agricultural species common wheat (Triticum aestivum L.) were grown in sand culture and exposed to supplemental concentrations of soluble Cu of 0 (control), 50, 100, 150, 200, 250, and 300 mg/L. We determined six measures of toxicity: the 60-d mean lethal concentration (LC50), 60-d mean effective concentration (EC50)-plant, 60-d EC50-shoot, 60-d EC50-root, phytotoxicity threshold (PT50)-shoot, and the PT50-root. Results suggest that these restoration grass species generally have higher Cu tolerance than agronomic species reported in the past. Of the species tested, redtop appeared to be especially tolerant of high levels of substrate and tissue Cu. Values of EC50-plant for restoration grasses were between 283 and 710 mg Cu/L compared to 120 mg Cu/L for common wheat. Measured PT50-shoot values were between 737 and 10,792 mg Cu/L. These reported thresholds should be more useful for risk assessors than those currently used, which are based largely on agronomic crops.

Adaptation, Physiological↗

A large DNA repeat of the dispersion pattern common to wheat and rye genomes.

A Hind III-generated fragment of wheat embryo nuclear DNA has been cloned and sequenced. The cloned fragment corresponds to a 1241 bp long, moderately repeated (60,000 copies/genome) segment of the genomic DNA. The repeat is AT-rich (67%), contains an open reading frame for 151 amino acids and several nucleotide blocks resembling the consensus domain of autonomously replicating sequences. Southern blot hybridization analyses indicate that the repeat is scattered through the wheat genome. A sequence homologous to this repeat occurs also in rye embryo nuclear DNA where it shows the same dispersion pattern as that observed for the wheat repeat.

Base Sequence↗