682 research outputs found
Molecular interaction of the gamma-clade homeodomain-leucine zipper class I transcription factors during the wheat response to water deficit
The ᵧ-clade of class I homeodomain-leucine zipper (HD-Zip I) transcription factors (TFs) constitute members which play a role in adapting plant growth to conditions of water deficit. Given the importance of wheat (Triticum aestivum L.) as a global food crop and the impact of water deficit upon grain yield, we focused on functional aspects of wheat drought responsive HD-Zip I TFs. While the wheat ᵧ-clade HD-Zip I TFs share significant sequence similarities with homologous genes from other plants, the clade-specific features in transcriptional response to abiotic stress were detected. We demonstrate that wheat TaHDZipI- 3, TaHDZipI-4, and TaHDZipI-5 genes respond differentially to a variety of abiotic stresses, and that proteins encoded by these genes exhibit pronounced differences in oligomerisation, strength of DNA binding, and trans-activation of an artificial promoter. Three-dimensional molecular modelling of the protein-DNA interface was conducted to address the ambiguity at the central nucleotide in the pseudo-palindromic cis-element CAATNATTG that is recognised by all three HD-Zip I proteins. The coexpression of these genes in the same plant tissues together with the ability of HD-Zip I TFs of the ᵧ -clade to heterodimerise suggests a role in the regulatory mechanisms of HD-Zip I dependent transcription. Our findings highlight the complexity of TF networks involved in plant responses to water deficit. A better understanding of the molecular complexity at the protein level during crop responses to drought will enable adoption of efficient strategies for production of cereal plants with enhanced drought tolerance.John C. Harris, Pradeep Sornaraj, Mathew Taylor, Natalia Bazanova, Ute Baumann, Ben Lovell, Peter Langridge, Sergiy Lopato, Maria Hrmov
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The stealth episome: suppression of gene expression on the excised genomic island PPHGI-1 from Pseudomonas syringae pv. phaseolicola
Pseudomonas syringae pv. phaseolicola is the causative agent of halo blight in the common bean, Phaseolus vulgaris. P. syringae pv. phaseolicola race 4 strain 1302A contains the avirulence gene avrPphB (syn. hopAR1), which resides on PPHGI-1, a 106 kb genomic island. Loss of PPHGI-1 from P. syringae pv. phaseolicola 1302A following exposure to the hypersensitive resistance response (HR) leads to the evolution of strains with altered virulence. Here we have used fluorescent protein reporter systems to gain insight into the mobility of PPHGI-1. Confocal imaging of dual-labelled P. syringae pv. phaseolicola 1302A strain, F532 (dsRFP in chromosome and eGFP in PPHGI-1), revealed loss of PPHGI-1::eGFP encoded fluorescence during plant infection and when grown in vitro on extracted leaf apoplastic fluids. Fluorescence-activated cell sorting (FACS) of fluorescent and non-fluorescent PPHGI-1::eGFP F532 populations showed that cells lost fluorescence not only when the GI was deleted, but also when it had excised and was present as a circular episome. In addition to reduced expression of eGFP, quantitative PCR on sub-populations separated by FACS showed that transcription of other genes on PPHGI-1 (avrPphB and xerC) was also greatly reduced in F532 cells harbouring the excised PPHGI-1::eGFP episome. Our results show how virulence determinants located on mobile pathogenicity islands may be hidden from detection by host surveillance systems through the suppression of gene expression in the episomal state
The TANAMI Program
TANAMI (Tracking Active Galactic Nuclei with Austral Milliarcsecond
Interferometry) is a monitoring program to study the parsec-scale structures
and dynamics of relativistic jets in active galactic nuclei (AGN) of the
Southern Hemisphere with the Long Baseline Array and associated telescopes.
Extragalactic jets south of -30 degrees declination are observed at 8.4 GHz and
22 GHz every two months at milliarcsecond resolution. The initial TANAMI sample
is a hybrid radio and gamma-ray selected sample since the combination of VLBI
and gamma-ray observations is crucial to understand the broadband emission
characteristics of AGN.Comment: Confernce Proceedings for "X-ray Astronomy 2009" (Bologna), 3 pages,
3 figures, needs cls-fil
Two alternative methods for the retrieval of somatic cell populations from the mouse ovary
Many modern techniques employed to uncover the molecular fundamentals underlying biological processes require dissociated cells as their starting point/substrate. Investigations into ovarian endocrinology or folliculogenesis therefore necessitate robust protocols for dissociating the ovary into its constituent cell populations. While in the mouse, methods to obtain individual, mature follicles are well-established, the separation and isolation of single cells of all types from early mouse follicles, including somatic cells, has been more challenging. Herein we present two methods for the isolation of somatic cells in the ovary. These methods are suitable for a range of applications relating to the study of folliculogenesis and mouse ovarian development. First, an enzymatic dissociation utilising collagenase and a temporary, primary cell culture step using neonatal mouse ovaries which yields large quantities of granulosa cells from primordial, activating, and primary follicles. Second, a rapid papain dissociation resulting in a high viability single cell suspension of ovarian somatic cells in less than an hour, which can be applied from embryonic to adult ovarian samples. Collectively these protocols can be applied to a broad array of investigations with unique advantages and benefits pertaining to both
Dual-frequency VLBI study of Centaurus A on sub-parsec scales
Centaurus A is the closest active galactic nucleus. High resolution imaging
using Very Long Baseline Interferometry (VLBI) enables us to study the spectral
and kinematic behavior of the radio jet-counterjet system on sub-parsec scales,
providing essential information for jet emission and formation models. Our aim
is to study the structure and spectral shape of the emission from the
central-parsec region of Cen A. As a target of the Southern Hemisphere VLBI
monitoring program TANAMI (Tracking Active Galactic Nuclei with Milliarcsecond
Interferometry), VLBI observations of Cen A are made regularly at 8.4 and 22.3
GHz with the Australian Long Baseline Array (LBA) and associated telescopes in
Antarctica, Chile, and South Africa. The first dual-frequency images of this
source are presented along with the resulting spectral index map. An angular
resolution of 0.4 mas x 0.7 mas is achieved at 8.4 GHz, corresponding to a
linear scale of less than 0.013 pc. Hence, we obtain the highest resolution
VLBI image of Cen A, comparable to previous space-VLBI observations. By
combining with the 22.3 GHz image, which has been taken without contributing
transoceanic baselines at somewhat lower resolution, we present the
corresponding dual-frequency spectral index distribution along the sub-parsec
scale jet revealing the putative emission regions for recently detected
gamma-rays from the core region by Fermi/LAT. We resolve the innermost
structure of the milliarcsecond scale jet and counterjet system of Cen A into
discrete components. The simultaneous observations at two frequencies provide
the highest resolved spectral index map of an AGN jet allowing us to identify
multiple possible sites as the origin of the high energy emission.Comment: 5 pages, 3 figures (1 color); A&A, accepte
TANAMI - Tracking Active Galactic Nuclei with Austral Milliarcsecond Interferometry
We present a summary of the observation strategy of TANAMI (Tracking Active
Galactic Nuclei with Austral Milliarcsecond Interferometry), a monitoring
program to study the parsec-scale structure and dynamics of relativistic jets
in active galactic nuclei (AGN) of the Southern Hemisphere with the Australian
Long Baseline Array (LBA) and the trans-oceanic antennas Hartebeesthoek, TIGO,
and O'Higgins. TANAMI is focusing on extragalactic sources south of -30 degrees
declination with observations at 8.4 GHz and 22 GHz every ~2 months at
milliarcsecond resolution. The initial TANAMI sample of 43 sources has been
defined before the launch of the Fermi Gamma Ray Space Telescope to include the
most promising candidates for bright gamma-ray emission to be detected with its
Large Area Telescope (LAT). Since November 2008, we have been adding new
sources to the sample, which now includes all known radio- and gamma-ray bright
AGN of the Southern Hemisphere. The combination of VLBI and gamma-ray
observations is crucial to understand the broadband emission characteristics of
AGN and the nature of relativistic jets.Comment: Conference proceedings "2009 Fermi Symposium" eConf Proceedings
C09112
Spending time in the garden is positively associated with health and wellbeing: Results from a national survey in England
This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordResearch has found that natural environments within urban areas are associated with benefits for human health and wellbeing. However, most studies have primarily focused on publically accessible green space. Less is known about domestic gardens, which in the UK comprise a high proportion of land cover in urban areas and could form a resource for health promotion. This study analysed secondary data from the Monitor of Engagement with the Natural Environment (MENE) survey, a representative survey of the English population (n = 7,814). We investigated the relationships between garden access and use and: general health; evaluative and eudaimonic wellbeing; meeting physical activity guidelines; and visiting nature in the last week. Statistical models included a range of individual and area-level socio-demographic variables. Compared to no garden access, access to a private garden was associated with better evaluative wellbeing, and people with access to a private space such as a balcony, yard or patio were more likely to meet physical activity guidelines. Respondents who reported both gardening and using a garden to relax also reported better health and wellbeing, more physical activity, and more nature visits than those who did not. These findings indicate that domestic gardens are a potential health resource and are not necessarily substituted for by other natural environments, highlighting the importance of their provision alongside green space in urban policy and planning.Innovate UKNational Institute for Health Research (NIHR
Blazars in the Fermi Era: The OVRO 40-m Telescope Monitoring Program
The Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space Telescope
provides an unprecedented opportunity to study gamma-ray blazars. To capitalize
on this opportunity, beginning in late 2007, about a year before the start of
LAT science operations, we began a large-scale, fast-cadence 15 GHz radio
monitoring program with the 40-m telescope at the Owens Valley Radio
Observatory (OVRO). This program began with the 1158 northern (declination>-20
deg) sources from the Candidate Gamma-ray Blazar Survey (CGRaBS) and now
encompasses over 1500 sources, each observed twice per week with a ~4 mJy
(minimum) and 3% (typical) uncertainty. Here, we describe this monitoring
program and our methods, and present radio light curves from the first two
years (2008 and 2009). As a first application, we combine these data with a
novel measure of light curve variability amplitude, the intrinsic modulation
index, through a likelihood analysis to examine the variability properties of
subpopulations of our sample. We demonstrate that, with high significance
(7-sigma), gamma-ray-loud blazars detected by the LAT during its first 11
months of operation vary with about a factor of two greater amplitude than do
the gamma-ray-quiet blazars in our sample. We also find a significant (3-sigma)
difference between variability amplitude in BL Lacertae objects and
flat-spectrum radio quasars (FSRQs), with the former exhibiting larger
variability amplitudes. Finally, low-redshift (z<1) FSRQs are found to vary
more strongly than high-redshift FSRQs, with 3-sigma significance. These
findings represent an important step toward understanding why some blazars emit
gamma-rays while others, with apparently similar properties, remain silent.Comment: 23 pages, 24 figures. Submitted to ApJ
Promises and challenges of eco-physiological genomics in the field: Tests of drought responses in switchgrass
© 2016 American Society of Plant Biologists. All rights reserved.Identifying the physiological and genetic basis of stress tolerance in plants has proven to be critical to understanding adaptation in both agricultural and natural systems. However, many discoveries were initially made in the controlled conditions of greenhouses or laboratories, not in the field. To test the comparability of drought responses across field and greenhouse environments, we undertook three independent experiments using the switchgrass reference genotype Alamo AP13. We analyzed physiological and gene expression variation across four locations, two sampling times, and three years. Relatively similar physiological responses and expression coefficients of variation across experiments masked highly dissimilar gene expression responses to drought. Critically, a drought experiment utilizing small pots in the greenhouse elicited nearly identical physiological changes as an experiment conducted in the field, but an order of magnitude more differentially expressed genes. However, we were able to define a suite of several hundred genes that were differentially expressed across all experiments. This list was strongly enriched in photosynthesis, water status, and reactive oxygen species responsive genes. The strong acrossexperiment correlations between physiological plasticity-but not differential gene expression-highlight the complex and diverse genetic mechanisms that can produce phenotypically similar responses to various soil water deficits
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