1,721,342 research outputs found
Estudios citogenéticos y evolutivos de las especies patagónicas del género Festuca (poaceae)
Get PDFFil: Dubcovsky, Jorge. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina
Estudios citogenéticos y evolutivos de las especies patagónicas del género Festuca (poaceae)
No full textFil: Dubcovsky, Jorge. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina
Exogenous gibberellins induce wheat spike development under short days only in the presence of VERNALIZATION1.
Get PDFThe activation of the meristem identity gene VERNALIZATION1 (VRN1) is a critical regulatory point in wheat (Triticum spp.) flowering. In photoperiod-sensitive wheat varieties, VRN1 is expressed only under long days (LDs), but mutants carrying deletions in a regulatory element in its promoter show VRN1 transcription and early spike development under short days (SDs). However, complete spike development is delayed until plants are transferred to LDs, indicating the existence of an additional regulatory mechanism dependent on LDs. We show here that exogenous gibberellin (GA) application accelerates spike development under SDs, but only in wheat lines expressing VRN1. The simultaneous presence of GA and VRN1 results in the up-regulation of the floral meristem identity genes SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1-1 and LEAFY, whereas inhibition of GA biosynthesis with paclobutrazol precludes the LD induction of these two genes. The inductive role of GA on wheat flowering is further supported by the up-regulation of GA biosynthetic genes in the apices of plants transferred from SDs to LDs and in photoperiod-insensitive and transgenic wheat plants with increased FLOWERING LOCUS T transcription under SDs. The up-regulation of GA biosynthetic genes was not observed in the leaves of the same genetic stocks. Based on these observations, we propose a model in which FLOWERING LOCUS T is up-regulated in the leaves under LDs and is then transported to the shoot apical meristem, where it simultaneously induces the expression of VRN1 and GA biosynthetic genes, which are both required for the up-regulation of the early floral meristem genes SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1-1 and LEAFY and the timely development of the wheat spike.Fil: Pearce, Stephen. University of California at Davis; Estados UnidosFil: Vanzetti, Leonardo Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias. Instituto de Fisiología y Recursos Genéticos Vegetales; ArgentinaFil: Dubcovsky, Jorge. Howard Hughes Medical Institute; Estados Unido
Physical mapping of durum wheat lipoxygenase genes
Get PDFA bright yellow color is an important quality criterion for pasta making. Yellow color depends on the amount of carotenoid pigments in grain, which is the result of the balance between pigment synthesis and degradation by lipoxygenases (LPX). The organization of genes coding for lipoxygenases in the tetraploid wheat genome is not completely understood. Here, we report the screening of a durum wheat BAC library with barley probes to characterize the physical distribution of Lpx genes. PCR characterization and BAC fingerprinting of the positive clones suggests that Lpx-B1.1 and Lpx-B3 are less than 103-kb apart, whereas Lpx-B1.2 is further apart from them. In the A genome a partially deleted copy of Lpx-1 (Lpx-A1_like) was found, colocalizing within a 42 kbp region with Lpx-A3, confirming that in both genomes these two genes are close to each other. The knowledge of the physical location of these two genes is important to understand the evolution of this family but also has practical implications since closely linked genes are difficult to separate by recombination. This may limit the number of Lpx allele combinations that can be obtained and affect the selection of optimal Lpx allele combinations for pasta quality improvement.Fil: Garbus, Ingrid. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; ArgentinaFil: Carrera, Alicia. Universidad Nacional del Sur. Departamento de Agronomía; ArgentinaFil: Dubcovsky, Jorge. University of California at Davis; Estados UnidosFil: Echenique, Carmen Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentina. Universidad Nacional del Sur. Departamento de Agronomía; Argentin
A genome-wide association study of resistance to stripe rust (Puccinia striiformis f. sp. tritici) in a worldwide collection of hexaploid spring wheat (Triticum aestivum L.)
Get PDFNew races of Puccinia striiformis f. sp. tritici (Pst), the causal pathogen of wheat stripe rust, show high virulence to previously deployed resistance genes and are responsible for large yield losses worldwide. To identify new sources of resistance we performed a genome-wide association study (GWAS) using a worldwide collection of 1000 spring wheat accessions. Adult plants were evaluated under field conditions in six environments in the western United States, and seedlings were tested with four Pst races. A single-nucleotide polymorphism (SNP) Infinium 9K-assay provided 4585 SNPs suitable for GWAS. High correlations among environments and high heritabilities were observed for stripe rust infection type and severity. Greater levels of Pst resistance were observed in a subpopulation from Southern Asia than in other groups. GWAS identified 97 loci that were significant for at least three environments, including 10 with an experiment-wise adjusted Bonferroni probability < 0.10. These 10 quantitative trait loci (QTL) explained 15% of the phenotypic variation in infection type, a percentage that increased to 45% when all QTL were considered. Three of these 10 QTL were mapped far from previously identified Pst resistance genes and QTL, and likely represent new resistance loci. The other seven QTL mapped close to known resistance genes and allelism tests will be required to test their relationships. In summary, this study provides an integrated view of stripe rust resistance resources in spring wheat and identifies new resistance loci that will be useful to diversify the current set of resistance genes deployed to control this devastating disease
Frequencies of Ty1-copia and Ty3-gypsy retroelements within the Triticeae EST databases
Get PDFThe frequency of Ty1-copia-type and Ty3-gypsy-type retrotransposons in the International Triticeae EST Consortium (ITEC) database (61,942 sequences: 82% wheat, 10% barley, 8% rye) and the DuPont EST database (86,628 wheat sequences) was estimated using BLASTN searches. These ESTs were obtained from 94 cDNA libraries from different tissues (leaves, roots, spikes, flowers and seeds) and different growing conditions, excluding subtracted and normalized cDNA libraries. Triticeae EST databases were screened using four different Ty1--copia-type, 12 reverse transcriptase sequences, and three Ty3-gypsy-type Triticeae retrotransposon sequences. Using a selection threshold of BLASTN scores higher than 100 or E values smaller than e–20, 0.145% of the ESTs were found to be significantly similar to at least one of the retrotransposons used in the search (0.064% Ty1-copia, 0.081% Ty3-gypsy). This percentage increased to 0.176% when the BLASTN threshold was changed to EFil: Echenique, Carmen Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentina. Universidad Nacional del Sur. Departamento de Agronomía; ArgentinaFil: Stamova, B.. University of California at Davis; Estados UnidosFil: Wolters, P.. Delaware Technology Park; Estados UnidosFil: Lazo, G.. Western Regional Research Center; Estados UnidosFil: Carollo, V.. Western Regional Research Center; Estados UnidosFil: Dubcovsky, Jorge. University of California at Davis; Estados Unido
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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Identification, Characterization, and Deployment of an FT-A2 Allele for Increased Grain Number and of its Interactor bZIPC1 in Wheat (Triticum L.)
Get PDFChapter one of this thesis describes the discovery and validation of a natural polymorphism in the A genome copy of the FLOWERING LOCUS T2 (FT2), a gene which increases spikelet number per spike (SNS) in wheat. A previous study indicated that loss-of-function mutations in FT2 increased SNS, but also decreased fertility, negating the positive effects on grain yield. Fortunately, we found a natural amino acid change in the FT-A2 protein at position 10 from aspartic acid (D) to alanine (A) (henceforth, D10A), that was associated with increased SNS and no negative effects on fertility. We used a high-density genetic map to delimit the candidate gene region to 28 genes, and then determined that among them only FT-A2 had a non-synonymous polymorphism (D10A) consistent in all studied mapping populations. We concluded that FT-A2 was likely the cause for the increased SNS and validated its effect in a hexaploid spring and winter wheat population.Investigating the frequency of the A10 allele, we found that while it was present in 56% of the common wheat accessions, it was present in less than 1% of the durum accessions analyzed. This rapid increase from durum wheat to common wheat suggests that the A10 allele had undergone positive selection in common wheat and may be a useful target for improving grain yield in durum and common wheat.
Chapter two of this thesis investigates the effects of the introgression of the FT-A2 A10 allele into four high-yielding durum wheat varieties. We found that all lines with the A10 allele had significantly higher SNS with no significant decreases in fertility. However, due to variety x FT-A2 interactions, grain number per spike (GNS) was significantly increased in only three of the four varieties. Unfortunately, the increases in SNS and GNS were offset by a significant decrease in kernel weight in all four varieties, resulting in no significant differences in spike yield or grain yield per plot. There was a significant negative correlation between GNS and thousand kernel weight (r = -0.42, P = 0.0006), which we hypothesize reflects source limitations in our environment that resulted in incomplete filling of the extra grains. Incorporation of the FT-A2 A10 allele into high bio-mass genotypes which are less source-limited and the evaluation of sister isogenic lines in different environments will be necessary to test the usefulness of this allele in durum breeding programs.
Chapter three of this thesis describes the identification and characterization of bZIPC1, a bZIP-containing transcription factor from the C-subfamily, which we identified utilizing a yeast-two hybrid screen with the FT2 protein as bait. Combined loss-of-functions mutations in bZIPC-A1 and bZIPC-B1 (bzipc1) in tetraploid wheat resulted in drastic reduction in SNS with a limited effect on heading date. Expression studies revealed that genes previously known to affect SNS were not significantly affected by the bzipc1 mutations, suggesting that bZIPC1 may affect SNS through a different pathway. Investigating the natural variation in the bZIPC-B1 region, revealed three major haplotypes (H1-H3), with the H1 haplotype showing significantly higher SNS, GNS, and spike yield than both the H2 and H3 haplotypes, as well as an increased frequency from the ancestral tetraploids to the modern durum and common wheat varieties. We developed markers of the two non-synonymous SNPs that differentiate the H1 haplotype from H2 and H3 so the H1 haplotype can be identified, introgressed, and deployed in wheat breeding programs
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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