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H W Rines - One of the best experts on this subject based on the ideXlab platform.
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production and characterization of maize Chromosome 9 radiation hybrids derived from an oat maize Addition line
Genetics, 2000Co-Authors: Oscar Rieralizarazu, E V Ananiev, H W Rines, M I Vales, Ronald L PhillipsAbstract:In maize (Zea mays L., 2n = 2x = 20), map-based cloning and genome organization studies are often complicated because of the complexity of the genome. Maize Chromosome Addition lines of hexaploid cultivated oat (Avena sativa L., 2n = 6x = 42), where maize Chromosomes can be individually manipulated, represent unique materials for maize genome analysis. Maize Chromosome Addition lines are particularly suitable for the dissection of a single maize Chromosome using radiation because cultivated oat is an allohexaploid in which multiple copies of the oat basic genome provide buffering to chromosomal aberrations and other mutations. Irradiation (gamma rays at 30, 40, and 50 krad) of a monosomic maize Chromosome 9 Addition line produced maize Chromosome 9 radiation hybrids (M9RHs)-oat lines possessing different fragments of maize Chromosome 9 including intergenomic translocations and modified maize Addition Chromosomes with internal and terminal deletions. M9RHs with 1 to 10 radiation-induced breaks per Chromosome were identified. We estimated that a panel of 100 informative M9RHs (with an average of 3 breaks per Chromosome) would allow mapping at the 0. 5- to 1.0-Mb level of resolution. Because mapping with maize Chromosome Addition lines and radiation hybrid derivatives involves assays for the presence or absence of a given marker, monomorphic markers can be quickly and efficiently mapped to a Chromosome region. Radiation hybrid derivatives also represent sources of region-specific DNA for cloning of genes or DNA markers.
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evidence for the coincident initiation of homolog pairing and synapsis during the telomere clustering bouquet stage of meiotic prophase
Journal of Cell Science, 2000Co-Authors: Hank W Bass, David A Agard, Oscar Rieralizarazu, E V Ananiev, Stefano J Bordoli, H W Rines, R L Phillips, John W Sedat, W Z CandeAbstract:To improve knowledge of the prerequisites for meiotic Chromosome segregation in higher eukaryotes, we analyzed the spatial distribution of a pair of homologs before and during early meiotic prophase. Three-dimensional images of fluorescence in situ hybridization (FISH) were used to localize a single pair of homologs in diploid nuclei of a Chromosome-Addition line of oat, oat-maize9b. The system provided a robust assay for pairing based on cytological colocalization of FISH signals. Using a triple labeling scheme for simultaneous imaging of chromatin, telomeres and the homolog pair, we determined the timing of pairing in relation to the onset of three sequential hallmarks of early meiotic prophase: chromatin condensation (the leptotene stage), meiotic telomere clustering (the bouquet stage) and the initiation of synapsis (the zygotene stage). We found that the two homologs were mostly unpaired up through middle leptotene, at which point their spherical cloud-like domains began to transform into elongated and stretched-out domains. At late leptotene, the homologs had completely reorganized into long extended fibers, and the beginning of the bouquet stage was conspicuously marked by the de novo clustering of telomeres at the nuclear periphery. The homologs paired and synapsed during the bouquet stage, consistent with the timing of pairing observed for several oat 5S rDNA loci. In summary, results from analysis of more than 100 intact nuclei lead us to conclude that pairing and synapsis of homologous Chromosomes are largely coincident processes, ruling out a role for premeiotic pairing in this system. These findings suggest that the genome-wide remodeling of chromatin and telomere-mediated nuclear reorganization are prerequisite steps to the DNA sequence-based homology-search process in higher eukaryotes.
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Chromosome specific molecular organization of maize zea mays l centromeric regions
Proceedings of the National Academy of Sciences of the United States of America, 1998Co-Authors: E V Ananiev, Ronald L Phillips, H W RinesAbstract:A set of oat–maize Chromosome Addition lines with individual maize (Zea mays L.) Chromosomes present in plants with a complete oat (Avena sativa L.) Chromosome complement provides a unique opportunity to analyze the organization of centromeric regions of each maize Chromosome. A DNA sequence, MCS1a, described previously as a maize centromere-associated sequence, was used as a probe to isolate cosmid clones from a genomic library made of DNA purified from a maize Chromosome 9 Addition line. Analysis of six cosmid clones containing centromeric DNA segments revealed a complex organization. The MCS1a sequence was found to comprise a portion of the long terminal repeats of a retrotransposon-like repeated element, termed CentA. Two of the six cosmid clones contained regions composed of a newly identified family of tandem repeats, termed CentC. Copies of CentA and tandem arrays of CentC are interspersed with other repetitive elements, including the previously identified maize retroelements Huck and Prem2. Fluorescence in situ hybridization revealed that CentC and CentA elements are limited to the centromeric region of each maize Chromosome. The retroelements Huck and Prem2 are dispersed along all maize Chromosomes, although Huck elements are present in an increased concentration around centromeric regions. Significant variation in the size of the blocks of CentC and in the copy number of CentA elements, as well as restriction fragment length variations were detected within the centromeric region of each maize Chromosome studied. The different proportions and arrangements of these elements and likely others provide each centromeric region with a unique overall structure.
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complex structure of knob dna on maize Chromosome 9 retrotransposon invasion into heterochromatin
Genetics, 1998Co-Authors: E V Ananiev, H W Rines, Ronald L PhillipsAbstract:The recovery of maize (Zea mays L.) Chromosome Addition lines of oat (Avena sativa L.) from oat x maize crosses enables us to analyze the structure and composition of specific regions, such as knobs, of individual maize Chromosomes. A DNA hybridization blot panel of eight individual maize Chromosome Addition lines revealed that 180-bp repeats found in knobs are present in each of these maize Chromosomes, but the copy number varies from approximately 100 to 25, 000. Cosmid clones with knob DNA segments were isolated from a genomic library of an oat-maize Chromosome 9 Addition line with the help of the 180-bp knob-associated repeated DNA sequence used as a probe. Cloned knob DNA segments revealed a complex organization in which blocks of tandemly arranged 180-bp repeating units are interrupted by insertions of other repeated DNA sequences, mostly represented by individual full size copies of retrotransposable elements. There is an obvious preference for the integration of retrotransposable elements into certain sites (hot spots) of the 180-bp repeat. Sequence microheterogeneity including point mutations and duplications was found in copies of 180-bp repeats. The 180-bp repeats within an array all had the same polarity. Restriction maps constructed for 23 cloned knob DNA fragments revealed the positions of polymorphic sites and sites of integration of insertion elements. Discovery of the interspersion of retrotransposable elements among blocks of tandem repeats in maize and some other organisms suggests that this pattern may be basic to heterochromatin organization for eukaryotes.
B. S. Gill - One of the best experts on this subject based on the ideXlab platform.
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a set of triticum aestivum aegilops speltoides robertsonian translocation lines
Theoretical and Applied Genetics, 2016Co-Authors: Wenxuan Liu, Bernd Friebe, Dalhoe Koo, B. S. GillAbstract:Here we report the production of a set of wheat - Aegilops speltoides Robertsonian translocations covering all Ae. speltoides Chromosome arms except the long arm of the homoeologous group 4 Chromosome. Aegilops speltoides of the Poaceae family is the most probable donor of the B and G genomes of polyploid Triticum species and also an important source of resistance to diseases and pests of wheat. Previously, we reported the production of a complete set of T aestivum-Ae. speltoides Chromosome Addition lines and a set of disomic S(B/A)-genome Chromosome substitution lines. The isolation of compensating Robertsonian translocations (RobTs) composed of alien Chromosome arms translocated to homoeologous wheat Chromosome arms is the important next step to exploit the genetic variation of a wild relative of wheat. Here, we report the development of molecular markers specific for the S-genome Chromosomes and their use in the isolation of a set of 13 compensating wheat-Ae. speltoides RobTs covering the S genome of Ae. speltoides except for the long arm of Chromosome 4S. Most of the RobTs were fully fertile and will facilitate mapping of genes to specific Chromosome arms and also will accelerate the introgression of agronomically useful traits from Ae. speltoides into wheat by homologous recombination.
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a novel robertsonian translocation event leads to transfer of a stem rust resistance gene sr52 effective against race ug99 from dasypyrum villosum into bread wheat
Theoretical and Applied Genetics, 2011Co-Authors: Michael O. Pumphrey, Bernd Friebe, Matthew N Rouse, Yue Jin, Robert L. Bowden, Peng Zhang, C Qian, B. S. GillAbstract:Stem rust (Puccinia graminis f. sp. tritici Eriks. & E. Henn.) (the causal agent of wheat stem rust) race Ug99 (also designated TTKSK) and its derivatives have defeated several important stem rust resistance genes widely used in wheat (Triticum aestivum L.) production, rendering much of the worldwide wheat acreage susceptible. In order to identify new resistance sources, a large collection of wheat relatives and genetic stocks maintained at the Wheat Genetic and Genomic Resources Center was screened. The results revealed that most accessions of the diploid relative Dasypyrum villosum (L.) Candargy were highly resistant. The screening of a set of wheat–D. villosum Chromosome Addition lines revealed that the wheat–D. villosum disomic Addition line DA6V#3 was moderately resistant to race Ug99. The objective of the present study was to produce and characterize compensating wheat–D. villosum whole arm Robertsonian translocations (RobTs) involving Chromosomes 6D of wheat and 6V#3 of D. villosum through the mechanism of centric breakage-fusion. Seven 6V#3-specific EST–STS markers were developed for screening F2 progeny derived from plants double-monosomic for Chromosomes 6D and 6V#3. Surprisingly, although 6D was the target Chromosome, all recovered RobTs involved Chromosome 6A implying a novel mechanism for the origin of RobTs. Homozygous translocations (T6AS·6V#3L and T6AL·6V#3S) with good plant vigor and full fertility were selected from F3 families. A stem rust resistance gene was mapped to the long arm 6V#3L in T6AS·6V#3L and was designated as Sr52. Sr52 is temperature-sensitive and is most effective at 16°C, partially effective at 24°C, and ineffective at 28°C. The T6AS·6V#3L stock is a new source of resistance to Ug99, is cytogenetically stable, and may be useful in wheat improvement.
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development of a complete set of triticum aestivum aegilops speltoides Chromosome Addition lines
Theoretical and Applied Genetics, 2000Co-Authors: Bernd Friebe, Shuhei Nasuda, N. A. Tuleen, Peng Zhang, B. S. GillAbstract:Aegilops speltoides Tausch (2n = 2x = 14, SS) is considered as the closest living relative of the B and G genomes of polyploid wheats. A complete set of Triticumaestivum L. cv Chinese Spring-Ae. speltoides whole Chromosomes and seven telosomic Addition lines was established. A low pairing accession was selected for the isolation of the Chromosome Addition lines. Except for Chromosomes 3S and 6S, which are presently only available as monosomic Additions, all other lines were recovered as disomic or ditelosomic Additions. The individual Ae. speltoides Chromosomes isolated in the wheat background were assayed for their genetic effects on plant phenotype and cytologically characterized in terms of Chromosome length, arm ratio, distribution of marker C-bands, and FISH sites using a Ae. speltoides-specific repetitive element, Gc1R-1, as a probe. The homoeology of the added Ae. speltoides Chromosomes was established by using a standard set of RFLP probes. No chromosomal rearrangements relative to wheat were detected.
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standard karyotype of triticum umbellulatum and the characterization of derived Chromosome Addition and translocation lines in common wheat
Theoretical and Applied Genetics, 1995Co-Authors: Bernd Friebe, Jiming Jiang, N. A. Tuleen, B. S. GillAbstract:A standard karyotype and a generalized idiogram of Triticum umbellulatum (syn. Aegilops umbellulata, 2n = 2x = 14) was established based on C-banding analysis of ten accessions of different geographic origin and individual T. umbellulatum Chromosomes in T. aestivum - T. umbellulatum Chromosome Addition lines. Monosomic (MA) and disomic (DA) T. aestivum - T. umbellulatum Chromosome Addition lines (DA1U = B, DA2U = D, MA4U = F, DA5U = C, DA6U = A, DA7U = E = G) and telosomic Addition lines (DA1US, DA1UL, DA2US, DA2UL, DA4UL, MA5US, (+ iso 5US), DA5UL, DA7US, DA7UL) were analyzed. Line H was established as a disomic Addition line for the translocated wheat - T. umbellulatum Chromosome T2DS·4US. Radiation-induced wheat - T. umbellulatum translocation lines resistant to leaf rust (Lr9) were identified as T40 = T6BL·6BS-6UL, T41 = T4BL·4BS-6UL, T44 = T2DS·2DL-6UL, T47 = 'Transfer' = T6BS·6BL-6UL and T52 = T7BL·7BS-6UL. Breakpoints and sizes of the transferred T. umbellulatum segments in these translocations were determined by in situ hybridization analysis using total genomic T. umbellulatum DNA as a probe.
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c banding and in situ hybridization analyses of agropyron intermedium a partial wheat x ag intermedium amphiploid and six derived Chromosome Addition lines
Theoretical and Applied Genetics, 1992Co-Authors: Bernd Friebe, B. S. Gill, Yasuhiko Mukai, Y CauderonAbstract:C-banded karyotypes of Agropyron intermedium (2n=6x=42, E1E2X), a partial amphiploid Triticum aestivum —Ag. intermedium (2n=8x=56, TAF46), and six derived Chromosome Addition lines, were analyzed. In Ag. intermedium, diagnostic C-bands were present on 14 pairs of Chromosomes, designated from A to N, while the remaining seven pairs, designated O to U, either lacked, or had only faint, C-bands and were not always identified unambiguously. All seven Ag. intermedium Chromosome pairs of the partial amphiploid TAF46, and the added Ag. intermedium Chromosomes present in the six derived Addition lines, were identified by their characteristic C-banding patterns. Chromosome morphology and banding patterns were similar to those of the corresponding Chromosomes present in the parent Ag. intermedium accession, suggesting that these Chromosomes were not structurally rearranged. In-situ hybridization, using a 18s.265s rDNA probe, showed that the Ag. intermedium Chromosomes 1Ai-1 and 5Ai-l present in the Addition lines L3 and L5 were carrying actively transcribed nucleolus organizer regions. The results are discussed with respect to the genomic relationships of these Chromosomes.
Bernd Friebe - One of the best experts on this subject based on the ideXlab platform.
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a set of triticum aestivum aegilops speltoides robertsonian translocation lines
Theoretical and Applied Genetics, 2016Co-Authors: Wenxuan Liu, Bernd Friebe, Dalhoe Koo, B. S. GillAbstract:Here we report the production of a set of wheat - Aegilops speltoides Robertsonian translocations covering all Ae. speltoides Chromosome arms except the long arm of the homoeologous group 4 Chromosome. Aegilops speltoides of the Poaceae family is the most probable donor of the B and G genomes of polyploid Triticum species and also an important source of resistance to diseases and pests of wheat. Previously, we reported the production of a complete set of T aestivum-Ae. speltoides Chromosome Addition lines and a set of disomic S(B/A)-genome Chromosome substitution lines. The isolation of compensating Robertsonian translocations (RobTs) composed of alien Chromosome arms translocated to homoeologous wheat Chromosome arms is the important next step to exploit the genetic variation of a wild relative of wheat. Here, we report the development of molecular markers specific for the S-genome Chromosomes and their use in the isolation of a set of 13 compensating wheat-Ae. speltoides RobTs covering the S genome of Ae. speltoides except for the long arm of Chromosome 4S. Most of the RobTs were fully fertile and will facilitate mapping of genes to specific Chromosome arms and also will accelerate the introgression of agronomically useful traits from Ae. speltoides into wheat by homologous recombination.
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a novel robertsonian translocation event leads to transfer of a stem rust resistance gene sr52 effective against race ug99 from dasypyrum villosum into bread wheat
Theoretical and Applied Genetics, 2011Co-Authors: Michael O. Pumphrey, Bernd Friebe, Matthew N Rouse, Yue Jin, Robert L. Bowden, Peng Zhang, C Qian, B. S. GillAbstract:Stem rust (Puccinia graminis f. sp. tritici Eriks. & E. Henn.) (the causal agent of wheat stem rust) race Ug99 (also designated TTKSK) and its derivatives have defeated several important stem rust resistance genes widely used in wheat (Triticum aestivum L.) production, rendering much of the worldwide wheat acreage susceptible. In order to identify new resistance sources, a large collection of wheat relatives and genetic stocks maintained at the Wheat Genetic and Genomic Resources Center was screened. The results revealed that most accessions of the diploid relative Dasypyrum villosum (L.) Candargy were highly resistant. The screening of a set of wheat–D. villosum Chromosome Addition lines revealed that the wheat–D. villosum disomic Addition line DA6V#3 was moderately resistant to race Ug99. The objective of the present study was to produce and characterize compensating wheat–D. villosum whole arm Robertsonian translocations (RobTs) involving Chromosomes 6D of wheat and 6V#3 of D. villosum through the mechanism of centric breakage-fusion. Seven 6V#3-specific EST–STS markers were developed for screening F2 progeny derived from plants double-monosomic for Chromosomes 6D and 6V#3. Surprisingly, although 6D was the target Chromosome, all recovered RobTs involved Chromosome 6A implying a novel mechanism for the origin of RobTs. Homozygous translocations (T6AS·6V#3L and T6AL·6V#3S) with good plant vigor and full fertility were selected from F3 families. A stem rust resistance gene was mapped to the long arm 6V#3L in T6AS·6V#3L and was designated as Sr52. Sr52 is temperature-sensitive and is most effective at 16°C, partially effective at 24°C, and ineffective at 28°C. The T6AS·6V#3L stock is a new source of resistance to Ug99, is cytogenetically stable, and may be useful in wheat improvement.
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Fate of Aegilops speltoides-derived, repetitive DNA sequences in diploid Aegilops species, wheat-Aegilops amphiploids and derived Chromosome Addition lines.
Cytogenetic and genome research, 2010Co-Authors: Sundip Kumar, Bernd Friebe, Bikram S. GillAbstract:The present study reports the cloning and characterization of an Aegilops speltoides -derived subtelomeric repeat, designated as pSp1B16. Clone pSp1B16 has 98% sequ
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development of a complete set of triticum aestivum aegilops speltoides Chromosome Addition lines
Theoretical and Applied Genetics, 2000Co-Authors: Bernd Friebe, Shuhei Nasuda, N. A. Tuleen, Peng Zhang, B. S. GillAbstract:Aegilops speltoides Tausch (2n = 2x = 14, SS) is considered as the closest living relative of the B and G genomes of polyploid wheats. A complete set of Triticumaestivum L. cv Chinese Spring-Ae. speltoides whole Chromosomes and seven telosomic Addition lines was established. A low pairing accession was selected for the isolation of the Chromosome Addition lines. Except for Chromosomes 3S and 6S, which are presently only available as monosomic Additions, all other lines were recovered as disomic or ditelosomic Additions. The individual Ae. speltoides Chromosomes isolated in the wheat background were assayed for their genetic effects on plant phenotype and cytologically characterized in terms of Chromosome length, arm ratio, distribution of marker C-bands, and FISH sites using a Ae. speltoides-specific repetitive element, Gc1R-1, as a probe. The homoeology of the added Ae. speltoides Chromosomes was established by using a standard set of RFLP probes. No chromosomal rearrangements relative to wheat were detected.
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standard karyotype of triticum umbellulatum and the characterization of derived Chromosome Addition and translocation lines in common wheat
Theoretical and Applied Genetics, 1995Co-Authors: Bernd Friebe, Jiming Jiang, N. A. Tuleen, B. S. GillAbstract:A standard karyotype and a generalized idiogram of Triticum umbellulatum (syn. Aegilops umbellulata, 2n = 2x = 14) was established based on C-banding analysis of ten accessions of different geographic origin and individual T. umbellulatum Chromosomes in T. aestivum - T. umbellulatum Chromosome Addition lines. Monosomic (MA) and disomic (DA) T. aestivum - T. umbellulatum Chromosome Addition lines (DA1U = B, DA2U = D, MA4U = F, DA5U = C, DA6U = A, DA7U = E = G) and telosomic Addition lines (DA1US, DA1UL, DA2US, DA2UL, DA4UL, MA5US, (+ iso 5US), DA5UL, DA7US, DA7UL) were analyzed. Line H was established as a disomic Addition line for the translocated wheat - T. umbellulatum Chromosome T2DS·4US. Radiation-induced wheat - T. umbellulatum translocation lines resistant to leaf rust (Lr9) were identified as T40 = T6BL·6BS-6UL, T41 = T4BL·4BS-6UL, T44 = T2DS·2DL-6UL, T47 = 'Transfer' = T6BS·6BL-6UL and T52 = T7BL·7BS-6UL. Breakpoints and sizes of the transferred T. umbellulatum segments in these translocations were determined by in situ hybridization analysis using total genomic T. umbellulatum DNA as a probe.
E V Ananiev - One of the best experts on this subject based on the ideXlab platform.
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production and characterization of maize Chromosome 9 radiation hybrids derived from an oat maize Addition line
Genetics, 2000Co-Authors: Oscar Rieralizarazu, E V Ananiev, H W Rines, M I Vales, Ronald L PhillipsAbstract:In maize (Zea mays L., 2n = 2x = 20), map-based cloning and genome organization studies are often complicated because of the complexity of the genome. Maize Chromosome Addition lines of hexaploid cultivated oat (Avena sativa L., 2n = 6x = 42), where maize Chromosomes can be individually manipulated, represent unique materials for maize genome analysis. Maize Chromosome Addition lines are particularly suitable for the dissection of a single maize Chromosome using radiation because cultivated oat is an allohexaploid in which multiple copies of the oat basic genome provide buffering to chromosomal aberrations and other mutations. Irradiation (gamma rays at 30, 40, and 50 krad) of a monosomic maize Chromosome 9 Addition line produced maize Chromosome 9 radiation hybrids (M9RHs)-oat lines possessing different fragments of maize Chromosome 9 including intergenomic translocations and modified maize Addition Chromosomes with internal and terminal deletions. M9RHs with 1 to 10 radiation-induced breaks per Chromosome were identified. We estimated that a panel of 100 informative M9RHs (with an average of 3 breaks per Chromosome) would allow mapping at the 0. 5- to 1.0-Mb level of resolution. Because mapping with maize Chromosome Addition lines and radiation hybrid derivatives involves assays for the presence or absence of a given marker, monomorphic markers can be quickly and efficiently mapped to a Chromosome region. Radiation hybrid derivatives also represent sources of region-specific DNA for cloning of genes or DNA markers.
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evidence for the coincident initiation of homolog pairing and synapsis during the telomere clustering bouquet stage of meiotic prophase
Journal of Cell Science, 2000Co-Authors: Hank W Bass, David A Agard, Oscar Rieralizarazu, E V Ananiev, Stefano J Bordoli, H W Rines, R L Phillips, John W Sedat, W Z CandeAbstract:To improve knowledge of the prerequisites for meiotic Chromosome segregation in higher eukaryotes, we analyzed the spatial distribution of a pair of homologs before and during early meiotic prophase. Three-dimensional images of fluorescence in situ hybridization (FISH) were used to localize a single pair of homologs in diploid nuclei of a Chromosome-Addition line of oat, oat-maize9b. The system provided a robust assay for pairing based on cytological colocalization of FISH signals. Using a triple labeling scheme for simultaneous imaging of chromatin, telomeres and the homolog pair, we determined the timing of pairing in relation to the onset of three sequential hallmarks of early meiotic prophase: chromatin condensation (the leptotene stage), meiotic telomere clustering (the bouquet stage) and the initiation of synapsis (the zygotene stage). We found that the two homologs were mostly unpaired up through middle leptotene, at which point their spherical cloud-like domains began to transform into elongated and stretched-out domains. At late leptotene, the homologs had completely reorganized into long extended fibers, and the beginning of the bouquet stage was conspicuously marked by the de novo clustering of telomeres at the nuclear periphery. The homologs paired and synapsed during the bouquet stage, consistent with the timing of pairing observed for several oat 5S rDNA loci. In summary, results from analysis of more than 100 intact nuclei lead us to conclude that pairing and synapsis of homologous Chromosomes are largely coincident processes, ruling out a role for premeiotic pairing in this system. These findings suggest that the genome-wide remodeling of chromatin and telomere-mediated nuclear reorganization are prerequisite steps to the DNA sequence-based homology-search process in higher eukaryotes.
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Chromosome specific molecular organization of maize zea mays l centromeric regions
Proceedings of the National Academy of Sciences of the United States of America, 1998Co-Authors: E V Ananiev, Ronald L Phillips, H W RinesAbstract:A set of oat–maize Chromosome Addition lines with individual maize (Zea mays L.) Chromosomes present in plants with a complete oat (Avena sativa L.) Chromosome complement provides a unique opportunity to analyze the organization of centromeric regions of each maize Chromosome. A DNA sequence, MCS1a, described previously as a maize centromere-associated sequence, was used as a probe to isolate cosmid clones from a genomic library made of DNA purified from a maize Chromosome 9 Addition line. Analysis of six cosmid clones containing centromeric DNA segments revealed a complex organization. The MCS1a sequence was found to comprise a portion of the long terminal repeats of a retrotransposon-like repeated element, termed CentA. Two of the six cosmid clones contained regions composed of a newly identified family of tandem repeats, termed CentC. Copies of CentA and tandem arrays of CentC are interspersed with other repetitive elements, including the previously identified maize retroelements Huck and Prem2. Fluorescence in situ hybridization revealed that CentC and CentA elements are limited to the centromeric region of each maize Chromosome. The retroelements Huck and Prem2 are dispersed along all maize Chromosomes, although Huck elements are present in an increased concentration around centromeric regions. Significant variation in the size of the blocks of CentC and in the copy number of CentA elements, as well as restriction fragment length variations were detected within the centromeric region of each maize Chromosome studied. The different proportions and arrangements of these elements and likely others provide each centromeric region with a unique overall structure.
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complex structure of knob dna on maize Chromosome 9 retrotransposon invasion into heterochromatin
Genetics, 1998Co-Authors: E V Ananiev, H W Rines, Ronald L PhillipsAbstract:The recovery of maize (Zea mays L.) Chromosome Addition lines of oat (Avena sativa L.) from oat x maize crosses enables us to analyze the structure and composition of specific regions, such as knobs, of individual maize Chromosomes. A DNA hybridization blot panel of eight individual maize Chromosome Addition lines revealed that 180-bp repeats found in knobs are present in each of these maize Chromosomes, but the copy number varies from approximately 100 to 25, 000. Cosmid clones with knob DNA segments were isolated from a genomic library of an oat-maize Chromosome 9 Addition line with the help of the 180-bp knob-associated repeated DNA sequence used as a probe. Cloned knob DNA segments revealed a complex organization in which blocks of tandemly arranged 180-bp repeating units are interrupted by insertions of other repeated DNA sequences, mostly represented by individual full size copies of retrotransposable elements. There is an obvious preference for the integration of retrotransposable elements into certain sites (hot spots) of the 180-bp repeat. Sequence microheterogeneity including point mutations and duplications was found in copies of 180-bp repeats. The 180-bp repeats within an array all had the same polarity. Restriction maps constructed for 23 cloned knob DNA fragments revealed the positions of polymorphic sites and sites of integration of insertion elements. Discovery of the interspersion of retrotransposable elements among blocks of tandem repeats in maize and some other organisms suggests that this pattern may be basic to heterochromatin organization for eukaryotes.
Ronald L Phillips - One of the best experts on this subject based on the ideXlab platform.
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production and characterization of maize Chromosome 9 radiation hybrids derived from an oat maize Addition line
Genetics, 2000Co-Authors: Oscar Rieralizarazu, E V Ananiev, H W Rines, M I Vales, Ronald L PhillipsAbstract:In maize (Zea mays L., 2n = 2x = 20), map-based cloning and genome organization studies are often complicated because of the complexity of the genome. Maize Chromosome Addition lines of hexaploid cultivated oat (Avena sativa L., 2n = 6x = 42), where maize Chromosomes can be individually manipulated, represent unique materials for maize genome analysis. Maize Chromosome Addition lines are particularly suitable for the dissection of a single maize Chromosome using radiation because cultivated oat is an allohexaploid in which multiple copies of the oat basic genome provide buffering to chromosomal aberrations and other mutations. Irradiation (gamma rays at 30, 40, and 50 krad) of a monosomic maize Chromosome 9 Addition line produced maize Chromosome 9 radiation hybrids (M9RHs)-oat lines possessing different fragments of maize Chromosome 9 including intergenomic translocations and modified maize Addition Chromosomes with internal and terminal deletions. M9RHs with 1 to 10 radiation-induced breaks per Chromosome were identified. We estimated that a panel of 100 informative M9RHs (with an average of 3 breaks per Chromosome) would allow mapping at the 0. 5- to 1.0-Mb level of resolution. Because mapping with maize Chromosome Addition lines and radiation hybrid derivatives involves assays for the presence or absence of a given marker, monomorphic markers can be quickly and efficiently mapped to a Chromosome region. Radiation hybrid derivatives also represent sources of region-specific DNA for cloning of genes or DNA markers.
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Chromosome specific molecular organization of maize zea mays l centromeric regions
Proceedings of the National Academy of Sciences of the United States of America, 1998Co-Authors: E V Ananiev, Ronald L Phillips, H W RinesAbstract:A set of oat–maize Chromosome Addition lines with individual maize (Zea mays L.) Chromosomes present in plants with a complete oat (Avena sativa L.) Chromosome complement provides a unique opportunity to analyze the organization of centromeric regions of each maize Chromosome. A DNA sequence, MCS1a, described previously as a maize centromere-associated sequence, was used as a probe to isolate cosmid clones from a genomic library made of DNA purified from a maize Chromosome 9 Addition line. Analysis of six cosmid clones containing centromeric DNA segments revealed a complex organization. The MCS1a sequence was found to comprise a portion of the long terminal repeats of a retrotransposon-like repeated element, termed CentA. Two of the six cosmid clones contained regions composed of a newly identified family of tandem repeats, termed CentC. Copies of CentA and tandem arrays of CentC are interspersed with other repetitive elements, including the previously identified maize retroelements Huck and Prem2. Fluorescence in situ hybridization revealed that CentC and CentA elements are limited to the centromeric region of each maize Chromosome. The retroelements Huck and Prem2 are dispersed along all maize Chromosomes, although Huck elements are present in an increased concentration around centromeric regions. Significant variation in the size of the blocks of CentC and in the copy number of CentA elements, as well as restriction fragment length variations were detected within the centromeric region of each maize Chromosome studied. The different proportions and arrangements of these elements and likely others provide each centromeric region with a unique overall structure.
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complex structure of knob dna on maize Chromosome 9 retrotransposon invasion into heterochromatin
Genetics, 1998Co-Authors: E V Ananiev, H W Rines, Ronald L PhillipsAbstract:The recovery of maize (Zea mays L.) Chromosome Addition lines of oat (Avena sativa L.) from oat x maize crosses enables us to analyze the structure and composition of specific regions, such as knobs, of individual maize Chromosomes. A DNA hybridization blot panel of eight individual maize Chromosome Addition lines revealed that 180-bp repeats found in knobs are present in each of these maize Chromosomes, but the copy number varies from approximately 100 to 25, 000. Cosmid clones with knob DNA segments were isolated from a genomic library of an oat-maize Chromosome 9 Addition line with the help of the 180-bp knob-associated repeated DNA sequence used as a probe. Cloned knob DNA segments revealed a complex organization in which blocks of tandemly arranged 180-bp repeating units are interrupted by insertions of other repeated DNA sequences, mostly represented by individual full size copies of retrotransposable elements. There is an obvious preference for the integration of retrotransposable elements into certain sites (hot spots) of the 180-bp repeat. Sequence microheterogeneity including point mutations and duplications was found in copies of 180-bp repeats. The 180-bp repeats within an array all had the same polarity. Restriction maps constructed for 23 cloned knob DNA fragments revealed the positions of polymorphic sites and sites of integration of insertion elements. Discovery of the interspersion of retrotransposable elements among blocks of tandem repeats in maize and some other organisms suggests that this pattern may be basic to heterochromatin organization for eukaryotes.