1,696 research outputs found
Carbonic anhydrases CA1 and CA4 function in atmospheric CO2-modulated disease resistance
Main conclusion Carbonic anhydrases CA1 and CA4 attenuate plant immunity and can contribute to altered disease resistance levels in response to changing atmospheric CO2 conditions. Abstract β-Carbonic anhydrases (CAs) play an important role in CO2 metabolism and plant development, but have also been implicated in plant immunity. Here we show that the bacterial pathogen Pseudomonas syringae and application of the microbe-associated molecular pattern (MAMP) flg22 repress CA1 and CA4 gene expression in Arabidopsis thaliana. Using the CA double-mutant ca1ca4, we provide evidence that CA1 and CA4 play an attenuating role in pathogen- and flg22-triggered immune responses. In line with this, ca1ca4 plants exhibited enhanced resistance against P. syringae, which was accompanied by an increased expression of the defense-related genes FRK1 and ICS1. Under low atmospheric CO2 conditions (150 ppm), when CA activity is typically low, the levels of CA1 transcription and resistance to P. syringae in wild-type Col-0 were similar to those observed in ca1ca4. However, under ambient (400 ppm) and elevated (800 ppm) atmospheric CO2 conditions, CA1 transcription was enhanced and resistance to P. syringae reduced. Together, these results suggest that CA1 and CA4 attenuate plant immunity and that differential CA gene expression in response to changing atmospheric CO2 conditions contribute to altered disease resistance levels
Priming of plant innate immunity by rhizobacteria and beta-aminobutyric acid: differences and similarities in regulation
P>Pseudomonas fluorescens WCS417r bacteria and beta-aminobutyric acid can induce disease resistance in Arabidopsis, which is based on priming of defence. In this study, we examined the differences and similarities of WCS417r- and beta-aminobutyric acid-induced priming. Both WCS417r and beta-aminobutyric acid prime for enhanced deposition of callose-rich papillae after infection by the oomycete Hyaloperonospora arabidopsis. This priming is regulated by convergent pathways, which depend on phosphoinositide- and ABA-dependent signalling components. Conversely, induced resistance by WCS417r and beta-aminobutyric acid against the bacterial pathogen Pseudomonas syringae are controlled by distinct NPR1-dependent signalling pathways. As WCS417r and beta-aminobutyric acid prime jasmonate- and salicylate-inducible genes, respectively, we subsequently investigated the role of transcription factors. A quantitative PCR-based genome-wide screen for putative WCS417r- and beta-aminobutyric acid-responsive transcription factor genes revealed distinct sets of priming-responsive genes. Transcriptional analysis of a selection of these genes showed that they can serve as specific markers for priming. Promoter analysis of WRKY genes identified a putative cis-element that is strongly over-represented in promoters of 21 NPR1-dependent, beta-aminobutyric acid-inducible WRKY genes. Our study shows that priming of defence is regulated by different pathways, depending on the inducing agent and the challenging pathogen. Furthermore, we demon-strated that priming is associated with the enhanced expression of transcription factors. New Phytologist (2009) 183: 419-431doi: 10.1111/j.1469-8137.2009.02851.x
Predicting arene rate coefficients with respect to hydroxyl and other free radicals in the gas-phase: a simple and effective method using a single topological descriptor
International audienceThe reactivity of aromatic compounds is of great relevance to pure and applied chemical disciplines, yet existing methods for estimating gas-phase rate coefficients for their reactions with free radicals lack accuracy and universality. Here a novel approach is taken, whereby strong relationships between rate coefficients of aromatic hydrocarbons and a Randi?-type topological index are investigated, optimized and developed into a method which requires no specialist software or computing power. Measured gas-phase rate coefficients for the reaction of aromatic hydrocarbons with OH radicals were correlated with a calculated Randi?-type index, and optimized by including a term for side chain length. Although this method is exclusively for use with hydrocarbons, it is more diverse than any single existing methodology since it incorporates alkenylbenzenes into correlations, and can be extended towards other radical species such as O(3P) (and tentatively NO3, H and Cl). A comparison (with species common to both techniques) is made between the topological approach advocated here and a popular approach based on electrophilic subsituent constants, where it compares favourably. A modelling study was carried out to assess the impact of using estimated rate coefficients as opposed to measured data in an atmospheric model. The difference in model output was negligible for a range of NOx concentrations, which implies that this method has utility in complex chemical models. Strong relationships (e.g. for OH, R2=0.96) between seemingly diverse compounds including benzene, multisubstituted benzenes with saturated, unsaturated, aliphatic and cyclic substitutions and the nonbenzenoid aromatic, azulene suggests that the Randi?-type index presented here represents a new and effective way of describing aromatic reactivity, based on a quantitative structure-activity relationship (QSAR)
COMET: a Lagrangian transport model for greenhouse gas emission estimation ? forward model technique and performance for methane
International audienceThe Lagrangian transport model COMET has been developed to evaluate emission estimates based on atmospheric concentration observations. This paper describes the model and its application in modelling the methane concentrations at the European stations Cabauw and Macehead. The COMET model captures in most cases both synoptic and diurnal variations of the concentrations as a function of time and in absolute size quite well. The explained variability by COMET of the mixed layer concentration for Cabauw varies from 50% to 84%; for all hourly observations in 2002 the explained variability is 71% with a RMSE of 112 ppb. The explained variability for Macehead is 48%. The most important model parameters were tested for their influence on model performance, but in general the model is not very sensitive to variations within acceptable limits. For a regionally and locally polluted continental site the COMET model shows only a small bias and a moderate random error, and therefore is considered to capture the influence of the sources on the concentration variations quite well. It is therefore concluded that inverse methods and more specifically the COMET model is suitable to be applied in deriving independent estimates of greenhouse gas emissions using Source-Receptor relationships
Католицька концепція міжрелігійного діалогу: зміна акцентів
In Arabidopsis roots, the transcription factor MYB72 plays a dual role in the onset of rhizobacteria-induced systemic resistance (ISR) and plant survival under conditions of limited iron availability. Previously, it was shown that MYB72 coordinates the expression of a gene module that promotes synthesis and excretion of iron-mobilizing phenolic compounds in the rhizosphere, a process involved in both iron acquisition and ISR signaling. Here, we show that volatile compounds (VOCs) from ISR-inducing Pseudomonas bacteria are important elicitors of MYB72. VOCs-induced MYB72 is co-expressed with the iron uptake-related genes FERRIC REDUCTION OXIDASE 2 (FRO2) and IRON-REGULATED TRANSPORTER 1 (IRT1) in a FER-LIKE IRON DEFICIENCY INDUCED TRANSCRIPTION FACTOR (FIT)-dependent manner, indicating that MYB72 is an intrinsic part of the plants’ iron acquisition response that is typically activated upon iron starvation. However, VOCs-induced MYB72 is activated independently of the iron availability in the root vicinity. Moreover, rhizobacterial VOCs-mediated induction of MYB72 requires photosynthesis-related signals, while iron deficiency in the rhizosphere can activate MYB72 in the absence of shoot-derived signals. Together, these results show that the ISR- and iron acquisition-related transcription factor MYB72 in Arabidopsis roots is activated by rhizobacterial volatiles and photosynthesis-related signals, and can enhance the iron acquisition capacity of roots independently of the iron availability in the rhizosphere. This work highlights the role of MYB72 in plant processes by which root microbiota simultaneously stimulate systemic immunity and activate the iron uptake machinery in their host plants
Characterization of Arabidopsis enhanced disease susceptibility mutants that are affected in systemically induced resistance
In Arabidopsis, the rhizobacterial strain Pseudomonas fluorescens WCS417r triggers jasmonate (JA)- and
ethylene (ET)-dependent induced systemic resistance (ISR) that is effective against different pathogens.
Arabidopsis genotypes unable to express rhizobacteria-mediated ISR against the bacterial pathogen
Pseudomonas syringae pv. tomato DC3000 (Pst DC3000) exhibit enhanced disease susceptibility towards
this pathogen. To identify novel components controlling induced resistance, we tested 11 Arabidopsis
mutants with enhanced disease susceptibility (eds) to pathogenic P. syringae bacteria for WCS417rmediated
ISR and pathogen-induced systemic acquired resistance (SAR). Mutants eds4-1, eds8-1 and
eds10-1 failed to develop WCS417r-mediated ISR, while mutants eds5-1 and eds12-1 failed to express
pathogen-induced SAR. Whereas eds5-1 is known to be blocked in salicylic acid (SA) biosynthesis,
analysis of eds12-1 revealed that its impaired SAR response is caused by reduced sensitivity to this
molecule. Analysis of the ISR-impaired eds mutants revealed that they are non-responsive to induction
of resistance by methyl jasmonate (MeJA) (eds4-1, eds8-1 and eds10-1), or the ET precursor 1-
aminocyclopropane-1-carboxylate (ACC) (eds4-1 and eds10-1). Moreover, eds4-1 and eds8-1 showed
reduced expression of the plant defensin gene PDF1.2 after MeJA and ACC treatment, which was
associated with reduced sensitivity to either ET (eds4-1) or MeJA (eds8-1). Although blocked in
WCS417r-, MeJA- and ACC-induced ISR, eds10-1 behaved normally for several other responses to MeJA
or ACC. The results indicate that EDS12 is required for SAR and acts downstream of SA, whereas EDS4,
EDS8 and EDS10 are required for ISR acting either in JA signalling (EDS8), ET signalling (EDS4), or
downstream JA and ET signalling (EDS10) in the ISR pathway
Powering sub-Saharan Africa’s urban revolution: An energy transitions approach
This paper develops a geographic understanding of urban energy transitions in subSaharan
African towns and cities. In doing so this paper seeks to critically reflect on the
value and limits of urban transitions analysis as a framework for understanding energy
networks beyond the largely integrated systems across the Global North. We explore how
these potentials and deficits can be addressed by examining promising developments
across a series of debates in urban studies that can help sensitise this approach to
energyscapes in the African context. By reviewing urban transi- tions analysis through
these debates the paper offers four important contributions to expand existing ways of
understanding energy transition. These include the particular urbanisation dynamics of
African towns ands cities, the need to locate the urban across energy regimes, the
agencies of various intermediaries and urban actors and the contested politics inherent in
the governing of energy networks. In the conclusion we reflect on the specific directions
that have emerged from the paper in relation to our contributions, offering a
geographically informed framework that allows us to better examine the challenges and
specificities of transition across these rapidly growing urban regions
Attenuation of pattern recognition receptor signaling is mediated by a MAP kinase kinase kinase
Pattern recognition receptors (PRRs) play a key role in plant and animal innate immunity. PRR binding of their cognate ligand triggers a signaling network and activates an immune response. Activation of PRR signaling must be controlled prior to ligand binding to prevent spurious signaling and immune activation. Flagellin perception in Arabidopsis through FLAGELLIN‐SENSITIVE 2 (FLS2) induces the activation of mitogen‐activated protein kinases (MAPKs) and immunity. However, the precise molecular mechanism that connects activated FLS2 to downstream MAPK cascades remains unknown. Here, we report the identification of a differentially phosphorylated MAP kinase kinase kinase that also interacts with FLS2. Using targeted proteomics and functional analysis, we show that MKKK7 negatively regulates flagellin‐triggered signaling and basal immunity and this requires phosphorylation of MKKK7 on specific serine residues. MKKK7 attenuates MPK6 activity and defense gene expression. Moreover, MKKK7 suppresses the reactive oxygen species burst downstream of FLS2, suggesting that MKKK7‐mediated attenuation of FLS2 signaling occurs through direct modulation of the FLS2 complex
Reclaiming the political : emancipation and critique in security studies
The critical security studies literature has been marked by a shared commitment towards the politicization of security – that is, the analysis of its assumptions, implications and the practices through which it is (re)produced. In recent years, however, politicization has been accompanied by a tendency to conceive security as connected with a logic of exclusion, totalization and even violence. This has resulted in an imbalanced politicization that weakens critique. Seeking to tackle this situation, the present article engages with contributions that have advanced emancipatory versions of security. Starting with, but going beyond, the so-called Aberystwyth School of security studies, the argument reconsiders the meaning of security as emancipation by making the case for a systematic engagement with the notions of reality and power. This revised version of security as emancipation strengthens critique by addressing political dimensions that have been underplayed in the critical security literature
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