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Search Results: 1 - 10 of 1613 matches for " Brad Day "
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Arabidopsis Actin-Depolymerizing Factor-4 Links Pathogen Perception, Defense Activation and Transcription to Cytoskeletal Dynamics
Katie Porter,Masaki Shimono,Miaoying Tian,Brad Day
PLOS Pathogens , 2012, DOI: 10.1371/journal.ppat.1003006
Abstract: The primary role of Actin-Depolymerizing Factors (ADFs) is to sever filamentous actin, generating pointed ends, which in turn are incorporated into newly formed filaments, thus supporting stochastic actin dynamics. Arabidopsis ADF4 was recently shown to be required for the activation of resistance in Arabidopsis following infection with the phytopathogenic bacterium Pseudomonas syringae pv. tomato DC3000 (Pst) expressing the effector protein AvrPphB. Herein, we demonstrate that the expression of RPS5, the cognate resistance protein of AvrPphB, was dramatically reduced in the adf4 mutant, suggesting a link between actin cytoskeletal dynamics and the transcriptional regulation of R-protein activation. By examining the PTI (PAMP Triggered Immunity) response in the adf4 mutant when challenged with Pst expressing AvrPphB, we observed a significant reduction in the expression of the PTI-specific target gene FRK1 (Flg22-Induced Receptor Kinase 1). These data are in agreement with recent observations demonstrating a requirement for RPS5 in PTI-signaling in the presence of AvrPphB. Furthermore, MAPK (Mitogen-Activated Protein Kinase)-signaling was significantly reduced in the adf4 mutant, while no such reduction was observed in the rps5-1 point mutation under similar conditions. Isoelectric focusing confirmed phosphorylation of ADF4 at serine-6, and additional in planta analyses of ADF4's role in immune signaling demonstrates that nuclear localization is phosphorylation independent, while localization to the actin cytoskeleton is linked to ADF4 phosphorylation. Taken together, these data suggest a novel role for ADF4 in controlling gene-for-gene resistance activation, as well as MAPK-signaling, via the coordinated regulation of actin cytoskeletal dynamics and R-gene transcription.
Speciation and fate of trace metals in estuarine sediments under reduced and oxidized conditions, Seaplane Lagoon, Alameda Naval Air Station (USA)
Susan Carroll, Peggy A O'Day, Brad Esser, Simon Randall
Geochemical Transactions , 2002, DOI: 10.1186/1467-4866-3-81
Abstract: The fate of these metals during dredging was evaluated by comparing in situ geochemistry with that of sediments oxidized by seawater in laboratory experiments. Cadmium and zinc pose the greatest hazard from dredging because their sulfides were highly reactive in seawater. However, their dissolved concentrations under oxic conditions were limited eventually by sorption to or co-precipitation with an iron (oxy)hydroxide. About 50% of the reacted CdS and 80% of the reacted ZnS were bonded to an oxide-substrate at the end of the 90-day oxidation experiment. Lead and chromium pose a minimal hazard from dredging because they are bonded to relatively insoluble carbonate, phosphate, phyllosilicate, or oxide minerals that are stable in seawater. These results point out the specific chemical behavior of individual metals in estuarine sediments, and the need for direct confirmation of metal speciation in order to constrain predictive models that realistically assess the fate of metals in urban harbors and coastal sediments.A recent evaluation of sediment contamination of surface waters in the United States by the US Environmental Protection Agency identified 96 watersheds, mostly urban harbors, containing metal and/or organic chemical contents that are potentially hazardous to aquatic biota.[1] These harbors and coastal sediments are contaminated from past and present industrial and military waste disposal practices. One such example is the estuary sediments of the East Outfall Site of the Seaplane Lagoon, at the former Naval Air Station (NAS) Alameda located on an island in San Francisco Bay, USA (Fig. 1). The most abundant metals in the sediments are cadmium, lead, chromium, zinc, copper, and nickel. Concentrations of these metal contaminants above background levels in San Francisco Bay result from a 57 year history of military and industrial activity at this site. From 1940 to 1975, the Seaplane Lagoon received about 300 million gallons of waste-water from industrial and st
mRNA-Seq Analysis of the Pseudoperonospora cubensis Transcriptome During Cucumber (Cucumis sativus L.) Infection
Elizabeth A. Savory, Bishwo N. Adhikari, John P. Hamilton, Brieanne Vaillancourt, C. Robin Buell, Brad Day
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0035796
Abstract: Pseudoperonospora cubensis, an oomycete, is the causal agent of cucurbit downy mildew, and is responsible for significant losses on cucurbit crops worldwide. While other oomycete plant pathogens have been extensively studied at the molecular level, Ps. cubensis and the molecular basis of its interaction with cucurbit hosts has not been well examined. Here, we present the first large-scale global gene expression analysis of Ps. cubensis infection of a susceptible Cucumis sativus cultivar, ‘Vlaspik’, and identification of genes with putative roles in infection, growth, and pathogenicity. Using high throughput whole transcriptome sequencing, we captured differential expression of 2383 Ps. cubensis genes in sporangia and at 1, 2, 3, 4, 6, and 8 days post-inoculation (dpi). Additionally, comparison of Ps. cubensis expression profiles with expression profiles from an infection time course of the oomycete pathogen Phytophthora infestans on Solanum tuberosum revealed similarities in expression patterns of 1,576–6,806 orthologous genes suggesting a substantial degree of overlap in molecular events in virulence between the biotrophic Ps. cubensis and the hemi-biotrophic P. infestans. Co-expression analyses identified distinct modules of Ps. cubensis genes that were representative of early, intermediate, and late infection stages. Collectively, these expression data have advanced our understanding of key molecular and genetic events in the virulence of Ps. cubensis and thus, provides a foundation for identifying mechanism(s) by which to engineer or effect resistance in the host.
Consciousness & Time: A Time-Based Model of the Evolution of Consciousness  [PDF]
Brad Bowins
Journal of Behavioral and Brain Science (JBBS) , 2017, DOI: 10.4236/jbbs.2017.71002
Abstract: A novel theoretical model is presented maintaining that consciousness evolved on the basis of time distinctions. Various models of time pertain to the existence of future, present and past. It is proposed that the future represents potentialities, the present the actualization of certain potentialities, and the past a record of actualized potentialities. Actualization of potentialities derives from micro quantum wave function collapses with specific constellations corresponding to macro level form. Consciousness provides for an awareness of potentialities being actualized in the present, the time frame of consciousness closely aligning with the time frame of potentialities being actualized in the moment. Evolution of such awareness is highly probable, given the ensuing motivation enabling behavior to be altered in the moment to minimize the actualization of maladaptive potentialities, and maximize the actualization of adaptive potentialities. The model also provides a logical proof for the occurrence of time distinctions.
Alternative Splicing of a Multi-Drug Transporter from Pseudoperonospora cubensis Generates an RXLR Effector Protein That Elicits a Rapid Cell Death
Elizabeth A. Savory, Cheng Zou, Bishwo N. Adhikari, John P. Hamilton, C. Robin Buell, Shin-Han Shiu, Brad Day
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0034701
Abstract: Pseudoperonospora cubensis, an obligate oomycete pathogen, is the causal agent of cucurbit downy mildew, a foliar disease of global economic importance. Similar to other oomycete plant pathogens, Ps. cubensis has a suite of RXLR and RXLR-like effector proteins, which likely function as virulence or avirulence determinants during the course of host infection. Using in silico analyses, we identified 271 candidate effector proteins within the Ps. cubensis genome with variable RXLR motifs. In extending this analysis, we present the functional characterization of one Ps. cubensis effector protein, RXLR protein 1 (PscRXLR1), and its closest Phytophthora infestans ortholog, PITG_17484, a member of the Drug/Metabolite Transporter (DMT) superfamily. To assess if such effector-non-effector pairs are common among oomycete plant pathogens, we examined the relationship(s) among putative ortholog pairs in Ps. cubensis and P. infestans. Of 271 predicted Ps. cubensis effector proteins, only 109 (41%) had a putative ortholog in P. infestans and evolutionary rate analysis of these orthologs shows that they are evolving significantly faster than most other genes. We found that PscRXLR1 was up-regulated during the early stages of infection of plants, and, moreover, that heterologous expression of PscRXLR1 in Nicotiana benthamiana elicits a rapid necrosis. More interestingly, we also demonstrate that PscRXLR1 arises as a product of alternative splicing, making this the first example of an alternative splicing event in plant pathogenic oomycetes transforming a non-effector gene to a functional effector protein. Taken together, these data suggest a role for PscRXLR1 in pathogenicity, and, in total, our data provide a basis for comparative analysis of candidate effector proteins and their non-effector orthologs as a means of understanding function and evolutionary history of pathogen effectors.
Expression Profiling of Cucumis sativus in Response to Infection by Pseudoperonospora cubensis
Bishwo N. Adhikari, Elizabeth A. Savory, Brieanne Vaillancourt, Kevin L. Childs, John P. Hamilton, Brad Day, C. Robin Buell
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0034954
Abstract: The oomycete pathogen, Pseudoperonospora cubensis, is the causal agent of downy mildew on cucurbits, and at present, no effective resistance to this pathogen is available in cultivated cucumber (Cucumis sativus). To better understand the host response to a virulent pathogen, we performed expression profiling throughout a time course of a compatible interaction using whole transcriptome sequencing. As described herein, we were able to detect the expression of 15,286 cucumber genes, of which 14,476 were expressed throughout the infection process from 1 day post-inoculation (dpi) to 8 dpi. A large number of genes, 1,612 to 3,286, were differentially expressed in pair-wise comparisons between time points. We observed the rapid induction of key defense related genes, including catalases, chitinases, lipoxygenases, peroxidases, and protease inhibitors within 1 dpi, suggesting detection of the pathogen by the host. Co-expression network analyses revealed transcriptional networks with distinct patterns of expression including down-regulation at 2 dpi of known defense response genes suggesting coordinated suppression of host responses by the pathogen. Comparative analyses of cucumber gene expression patterns with that of orthologous Arabidopsis thaliana genes following challenge with Hyaloperonospora arabidopsidis revealed correlated expression patterns of single copy orthologs suggesting that these two dicot hosts have similar transcriptional responses to related pathogens. In total, the work described herein presents an in-depth analysis of the interplay between host susceptibility and pathogen virulence in an agriculturally important pathosystem.
The Plant Actin Cytoskeleton Responds to Signals from Microbe-Associated Molecular Patterns
Jessica L. Henty-Ridilla,Masaki Shimono,Jiejie Li,Jeff H. Chang,Brad Day ,Christopher J. Staiger
PLOS Pathogens , 2013, DOI: 10.1371/journal.ppat.1003290
Abstract: Plants are constantly exposed to a large and diverse array of microbes; however, most plants are immune to the majority of potential invaders and susceptible to only a small subset of pathogens. The cytoskeleton comprises a dynamic intracellular framework that responds rapidly to biotic stresses and supports numerous fundamental cellular processes including vesicle trafficking, endocytosis and the spatial distribution of organelles and protein complexes. For years, the actin cytoskeleton has been assumed to play a role in plant innate immunity against fungi and oomycetes, based largely on static images and pharmacological studies. To date, however, there is little evidence that the host-cell actin cytoskeleton participates in responses to phytopathogenic bacteria. Here, we quantified the spatiotemporal changes in host-cell cytoskeletal architecture during the immune response to pathogenic and non-pathogenic strains of Pseudomonas syringae pv. tomato DC3000. Two distinct changes to host cytoskeletal arrays were observed that correspond to distinct phases of plant-bacterial interactions i.e. the perception of microbe-associated molecular patterns (MAMPs) during pattern-triggered immunity (PTI) and perturbations by effector proteins during effector-triggered susceptibility (ETS). We demonstrate that an immediate increase in actin filament abundance is a conserved and novel component of PTI. Notably, treatment of leaves with a MAMP peptide mimic was sufficient to elicit a rapid change in actin organization in epidermal cells, and this actin response required the host-cell MAMP receptor kinase complex, including FLS2, BAK1 and BIK1. Finally, we found that actin polymerization is necessary for the increase in actin filament density and that blocking this increase with the actin-disrupting drug latrunculin B leads to enhanced susceptibility of host plants to pathogenic and non-pathogenic bacteria.
Influence of deficit irrigation on nutrient indices in wine grape (Vitis vinifera L.)  [PDF]
Krista Shellie, Brad Brown
Agricultural Sciences (AS) , 2012, DOI: 10.4236/as.2012.32031
Abstract: Deficit irrigation is widely used in wine grape production (Vitis vinifera L.) to meet wine quality goals yet its influence on tissue nutrient indices has not been well studied. The objective of this research was to determine whether response to water deficit compromised the prescriptive usefulness of tissue nutrient analyses. Tissue macro and micronutrient composition at bloom and veraison were evaluated over multiple seasons in nine wine grape cultivars grown under well-watered or deficit-irrigated conditions. Deficit-irrigated vines sampled at veraison had 2 to 12-fold higher petiole nitrate-nitrogen concentration, 6% lower blade nitrogen concentration and 13% lower blade copper concentration compared to well-watered vines. Water deficit influenced blade potassium concentration at veraison differently according to cultivar and was lower (cv. Malbec, Petite syrah, Viognier, Lemberger and Sangiovese), higher (cv. Merlot, Cabernet franc and Cabernet Sauvignon) or similar (cv. Grenache) to well-watered vines. Results from this study indicate that nutrient analysis of petiole or blade tissue sampled at veraison has limited diagnostic and prescriptive usefulness when vines are grown under a water deficit.
Folk-Linguistic Attitudes in Eastern Massachusetts  [PDF]
Rebecca Day Babcock
Open Journal of Modern Linguistics (OJML) , 2014, DOI: 10.4236/ojml.2014.43035

Folk linguistics attempts to study people’s beliefs and attitudes about language through their metalinguistic statements, usually collected in a naturalistic setting. Data was collected in a semistructured focus group setting with 11 white, middle- and working-class participants from Eastern Massachusetts. Participants spoke freely about linguistic topics. The results showed that the group focused their discussion on the speech of politicians (former Boston Mayor Tom Menino to be exact), linguistic status markers, specific features (r- and g-dropping, broad /a/), regions (local Massachusetts regions and Tennessee), and ethnicity (Black and Hispanic). All topics were introduced by the participants, rather than by the researcher.

Novel Insights into Disseminated Candidiasis: Pathogenesis Research and Clinical Experience Converge
Brad Spellberg
PLOS Pathogens , 2008, DOI: 10.1371/journal.ppat.0040038
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