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  • 1
    Publication Date: 2015-05-12
    Description: The shoot apical meristem contains a pool of undifferentiated stem cells and controls initiation of all aerial plant organs. In maize ( Zea mays ), leaves are formed throughout vegetative development; on transition to floral development, the shoot meristem forms the tassel. Due to the regulated balance between stem cell maintenance and organogenesis, the structure and morphology of the shoot meristem are constrained during vegetative development. Previous work identified loci controlling meristem architecture in a recombinant inbred line population. The study presented here expanded on this by investigating shoot apical meristem morphology across a diverse set of maize inbred lines. Crosses of these lines to common parents showed varying phenotypic expression in the F1, with some form of heterosis occasionally observed. An investigation of meristematic growth throughout vegetative development in diverse lines linked the timing of reproductive transition to flowering time. Phenotypic correlations of meristem morphology with adult plant traits showed an association between the meristem and flowering time, leaf shape, and yield traits, revealing links between the control and architecture of undifferentiated and differentiated plant organs. Finally, quantitative trait loci mapping was utilized to map the genetic architecture of these meristem traits in two divergent populations. Control of meristem architecture was mainly population-specific, with 15 total unique loci mapped across the two populations with only one locus identified in both populations.
    Electronic ISSN: 2160-1836
    Topics: Biology
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  • 2
    Publication Date: 2014-07-18
    Description: The shoot apical meristem contains a pool of undifferentiated stem cells and generates all above-ground organs of the plant. During vegetative growth, cells differentiate from the meristem to initiate leaves while the pool of meristematic cells is preserved; this balance is determined in part by genetic regulatory mechanisms. To assess vegetative meristem growth and genetic control in Zea mays , we investigated its morphology at multiple time points and identified three stages of growth. We measured meristem height, width, plastochron internode length, and associated traits from 86 individuals of the intermated B73 x Mo17 recombinant inbred line population. For meristem height-related traits, the parents exhibited markedly different phenotypes, with B73 being very tall, Mo17 short, and the population distributed between. In the outer cell layer, differences appeared to be related to number of cells rather than cell size. In contrast, B73 and Mo17 were similar in meristem width traits and plastochron internode length, with transgressive segregation in the population. Multiple loci (6–9 for each trait) were mapped, indicating meristem architecture is controlled by many regions; none of these coincided with previously described mutants impacting meristem development. Major loci for height and width explaining 16% and 19% of the variation were identified on chromosomes 5 and 8, respectively. Significant loci for related traits frequently coincided, whereas those for unrelated traits did not overlap. With the use of three near-isogenic lines, a locus explaining 16% of the parental variation in meristem height was validated. Published expression data were leveraged to identify candidate genes in significant regions.
    Electronic ISSN: 2160-1836
    Topics: Biology
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  • 3
    Publication Date: 2012-10-19
    Description: Barley (Hordeum vulgare L.) is among the world's earliest domesticated and most important crop plants. It is diploid with a large haploid genome of 5.1 gigabases (Gb). Here we present an integrated and ordered physical, genetic and functional sequence resource that describes the barley gene-space in a structured whole-genome context. We developed a physical map of 4.98 Gb, with more than 3.90 Gb anchored to a high-resolution genetic map. Projecting a deep whole-genome shotgun assembly, complementary DNA and deep RNA sequence data onto this framework supports 79,379 transcript clusters, including 26,159 'high-confidence' genes with homology support from other plant genomes. Abundant alternative splicing, premature termination codons and novel transcriptionally active regions suggest that post-transcriptional processing forms an important regulatory layer. Survey sequences from diverse accessions reveal a landscape of extensive single-nucleotide variation. Our data provide a platform for both genome-assisted research and enabling contemporary crop improvement.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉International Barley Genome Sequencing Consortium -- Mayer, Klaus F X -- Waugh, Robbie -- Brown, John W S -- Schulman, Alan -- Langridge, Peter -- Platzer, Matthias -- Fincher, Geoffrey B -- Muehlbauer, Gary J -- Sato, Kazuhiro -- Close, Timothy J -- Wise, Roger P -- Stein, Nils -- BB/100663X/1/Biotechnology and Biological Sciences Research Council/United Kingdom -- England -- Nature. 2012 Nov 29;491(7426):711-6. doi: 10.1038/nature11543. Epub 2012 Oct 17.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23075845" target="_blank"〉PubMed〈/a〉
    Keywords: Alternative Splicing/genetics ; Codon, Nonsense/genetics ; Crops, Agricultural/genetics ; Evolution, Molecular ; Gene Expression Regulation, Plant ; Genes, Plant/genetics ; Genome, Plant/*genetics ; Genomics ; Hordeum/classification/*genetics ; Molecular Sequence Annotation ; Physical Chromosome Mapping ; Polymorphism, Single Nucleotide/genetics ; Repetitive Sequences, Nucleic Acid/genetics ; *Sequence Analysis, DNA ; Transcriptome/genetics
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 4
    ISSN: 1432-2242
    Keywords: Key words Barley ; BAC library ; P-loop genes ; Resistance-gene analog (RGA)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Modern cultivated barley is an important cereal crop with an estimated genome size of 5000 Mb. To develop the resources for positional cloning and structural genomic analyses in barley, we constructed a bacterial artificial chromosome (BAC) library for the cultivar Morex using the cloning enzyme HindIII. The library contains 313344 clones (816 384-well plates). A random sampling of 504 clones indicated an average insert size of 106 kbp (range=30–195 kbp) and 3.4% empty vectors. Screening the colony filters for chloroplast DNA content indicated an exceptionally low 1.5% contamination with chloroplast DNA. Thus, the library provides 6.3 haploid genome equivalents allowing a 〉99% probability of recovering any specific sequence of interest. High-density filters were gridded robotically using a Genetix Q-BOT in a 4×4 double-spotted array on 22.5-cm2 filters. Each set of 17 filters allows the entire library to be screened with 18432 clones represented per filter. Screening the library with 40 single copy probes identified an average 6.4 clones per probe, with a range of 1–13 clones per probe. A set of resistance-gene analog (RGA) sequences identified 121 RGA-containing BAC clones representing 20 different regions of the genome with an average of 6.1 clones per locus. Additional screening of the library with a P-loop disease resistance primer probe identified 459 positive BAC clones. These data indicate that this library is a valuable resource for structural genomic applications in barley.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-2242
    Keywords: Glycine max ; Near-isogenic lines ; Molecular markers ; RFLP ; Linkage ; Genetic map
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A molecular marker analysis of a near-isogenic line (NIL), its donor parent (DP), and its recurrent parent (RP) can provide information about linkages between molecular markers and a conventional marker introgressed into the NIL. If the DP and RP possess different alleles for a given molecular marker, and if the NIL possesses the same allele as the DP, then it is reasonable to presume a linkage between that molecular marker and the introgressed marker. In this study, we examined the utility of RFLPs as molecular markers for the NIL genemapping approach. The allelic status of fifteen RFLP loci was determined in 116 soybean RP/NIL/DP line sets; 66 of the ‘Clark’ RP type and 50 of the ‘Harosoy’ RP type. Of the 1740 possible allelic comparisons (116 NILs x 15 RFLP loci), 1638 were tested and 462 (33.9%) of those were informative (i.e., the RP and DP had different RFLP alleles). In 15 (3.2%) of these 462 cases the NIL possessed the DP-derived RFLP allele, leading to a presumption of linkage between the RFLP locus and the introgressed conventional marker locus. Two presumptive linkages, pK-3 — and pK-472 — Lf i, were subsequently confirmed by cosegregation linkage analysis. Although not yet confirmed, two other associations, pk-7 ab and pK-229 — y 9 seemed to be plausible linkages, primarily because the pk-7 — ab association was detected in two independently derived NILs and both markers of the pK-229 — y 9 association were known to be linked to Pb. The data obtained in this investigation indicated that RFLP loci were useful molecular markers for the NIL gene-mapping technique.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-2242
    Keywords: Zea mays ; Aspartate kinase Threonine-overproducing mutants ; Lysine ; Methionine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The aspartate-derived amino-acid pathway leads to the production of the essential amino-acids lysine, methionine, threonine and isoleucine. Aspartate kinase (AK) is the first enzyme in this pathway and exists in isoforms that are feedback inhibited by lysine and threonine. Two maize (Zea mays L.) threonine-overproducing, lysine-insensitive AK mutants (Ask1-LT19 and Ask2-LT20) were previously isolated. The present study was conducted to determine the map location of Ask2 and to examine the amino-acid profiles of the Ask mutants. The threonine-overproducing trait conferred by Ask2-LT20 was mapped to the long arm of chromosome 2. Both mutants exhibited increased free threonine concentrations (nmol/mg dry weight) over wild-type. The percent free threonine increased from approximately 2% in wild-type kernels to 37–54% of the total free amino-acid pool in homozygous mutant kernels. Free methionine concentrations also increased significantly in homozygous mutants. Free lysine concentrations were increased but to a much lesser extent than threonine or methionine. In contrast to previous studies, free aspartate concentrations were observed to decrease, indicating a possible limiting factor in threonine synthesis. Total (free plus protein-bound) amino-acid analyses demonstrated a consistent, significant increase in threonine, methionine and lysine concentrations in the homozygous mutants. Significant increases in protein-bound (total minus free) threonine, methionine and lysine were observed in the Ask mutants, indicating adequate protein sinks to incorporate the increased free amino-acid concentrations. Total amino-acid contents (nmol/kernel) were approximately the same for mutant and wild-type kernels. In five inbred lines both Ask mutations conferred the threonine-overproducing phenotype, indicating high expressivity in different genetic backgrounds. These analyses are discussed in the context of the regulation of the aspartate-derived amino-acid pathway.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-2242
    Keywords: Key words Fusarium head blight ; Scab ; Kernel discoloration ; Black point ; Kernel blight ; Deoxynivalenol (DON) ; RFLP ; Barley
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Resistance to Fusarium head blight (FHB), deoxynivalenol (DON) accumulation, and kernel discoloration (KD) in barley are difficult traits to introgress into elite varieties because current screening methods are laborious and disease levels are strongly influenced by environment. To improve breeding strategies directed toward enhancing these traits, we identified genomic regions containing quantitative trait loci (QTLs) associated with resistance to FHB, DON accumulation, and KD in a breeding population of F4:7 lines using restriction fragment length polymorphic (RFLP) markers. We evaluated 101 F4:7 lines, derived from a cross between the cultivar Chevron and an elite breeding line, M69, for each of the traits in three or four environments. We used 94 previously mapped RFLP markers to create a linkage map. Using composite interval mapping, we identified 10, 11, and 4 QTLs associated with resistance to FHB, DON accumulation, and KD, respectively. Markers flanking these QTLs should be useful for introgressing resistance to FHB, DON accumulation, and KD into elite barley cultivars.
    Type of Medium: Electronic Resource
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  • 8
    Publication Date: 1989-11-01
    Print ISSN: 0011-183X
    Electronic ISSN: 1435-0653
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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  • 9
    Publication Date: 2014-07-18
    Description: Genetic differentiation in natural populations is driven by geographic distance and by ecological or physical features within and between natural habitats that reduce migration. The primary population structure in wild barley differentiates populations east and west of the Zagros Mountains. Genetic differentiation between eastern and western populations is uneven across the genome and is greatest on linkage groups 2H and 5H. Genetic markers in these two regions demonstrate the largest difference in frequency between the primary populations and have the highest informativeness for assignment to each population. Previous cytological and genetic studies suggest there are chromosomal structural rearrangements (inversions or translocations) in these genomic regions. Environmental association analyses identified an association with both temperature and precipitation variables on 2H and with precipitation variables on 5H.
    Electronic ISSN: 2160-1836
    Topics: Biology
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  • 10
    Publication Date: 2016-03-04
    Description: Barley was introduced to North America ~400 yr ago but adaptation to modern production environments is more recent. Comparisons of allele frequencies among growth habits and spike (inflorescence) types in North America indicate that significant genetic differentiation has accumulated in a relatively short evolutionary time span. Allele frequency differentiation is greatest among barley with two-row vs. six-row spikes, followed by spring vs. winter growth habit. Large changes in allele frequency among breeding programs suggest a major contribution of genetic drift and linked selection on genetic variation. Despite this, comparisons of 3613 modern North American cultivated barley breeding lines that differ for spike-type and growth habit permit the discovery of 142 single nucleotide polymorphism (SNP) outliers putatively linked to targets of selection. For example, SNPs within the Cbf4 , Ppd-H1 , and Vrn-H1 loci, which have previously been associated with agronomically adaptive phenotypes, are identified as outliers. Analysis of extended haplotype sharing identifies genomic regions shared within and among breeding populations, suggestive of a number of genomic regions subject to recent selection. Finally, we are able to identify recent bouts of gene flow between breeding populations that could point to the sharing of agronomically adaptive variation. These results are supported by pedigrees and breeders’ understanding of germplasm sharing.
    Electronic ISSN: 2160-1836
    Topics: Biology
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