Dark matter elastic scattering off nuclei can result in the excitation and ionization of the recoiling atom through the so-called Migdal effect. The energy deposition from the ionization electron ...adds to the energy deposited by the recoiling nuclear system and allows for the detection of interactions of sub-GeV/c^{2} mass dark matter. We present new constraints for sub-GeV/c^{2} dark matter using the dual-phase liquid argon time projection chamber of the DarkSide-50 experiment with an exposure of (12 306±184) kg d. The analysis is based on the ionization signal alone and significantly enhances the sensitivity of DarkSide-50, enabling sensitivity to dark matter with masses down to 40 MeV/c^{2}. Furthermore, it sets the most stringent upper limit on the spin independent dark matter nucleon cross section for masses below 3.6 GeV/c^{2}.
We present a search for dark matter particles with sub-GeV/c^{2} masses whose interactions have final state electrons using the DarkSide-50 experiment's (12 306±184) kg d low-radioactivity liquid ...argon exposure. By analyzing the ionization signals, we exclude new parameter space for the dark matter-electron cross section σover ¯_{e}, the axioelectric coupling constant g_{Ae}, and the dark photon kinetic mixing parameter κ. We also set the first dark matter direct-detection constraints on the mixing angle |U_{e4}|^{2} for keV/c^{2} sterile neutrinos.
Plants respond to biotic and abiotic factors in the external environment. These include wounding, pathogen and pest attack, and changes in light and temperature. They also respond to internal signals ...produced during development, such as during the formation of flowers. These responses generally involve the re‐programming of gene expression. Biotic and abiotic stress signal perception responses have commonly been represented as three pathways, which can be distinguished by the production of jasmonates, ethylene or salicylic acid. Each of these pathways therefore involves the perception of the stress, the synthesis of the signal molecule, the perception of the signal molecule and the ensuing response. An added complication is that these signalling pathways act both locally, at the point of the stress, and systemically. Much of what we know about these signalling pathways has come from studies of responses to the signal molecules, and of mutants altered in the production of, or sensitivity to, these signal molecules. This has provided clear indications that the pathways interact significantly. Because biotic and abiotic stresses induce the production of all three of these signal molecules, albeit in differing amounts, it is more appropriate to view the response output as the integration of a signalling network that involves the production of jasmonates, salicylic acid and ethylene.
In this review, we provide an update on the regulation of jasmonic acid biosynthesis and the suggested roles for different biologically active intermediates in this pathway in Arabidopsis, and describe the jasmonate signalling mutants identified so far. We also examine how outputs from the jasmonate, salicylic acid and ethylene signalling pathways are integrated in the regulation of stress response and plant development. We use Boolean gates as a tool to represent the molecular networks and provide a qualitative description of the transmission of the signals. Finally, we illustrate how protein degradation, a common mechanism regulating many plant processes, may act as the ultimate level of integration between signalling pathways.
Introduction: The Epworth sleepiness scale (ESS) is widely used as a way of measuring subjective sleep propensity in research and clinical practice. Psychometric studies do not rule out the presence ...of more than one latent dimension underlying the items.
Objective: Aims of the present study were to: (a) evaluate psychometric proprieties of the ESS by means of classic psychometric techniques; (b) compare them with those from a newly developed resistance to sleepiness scale (RSS); (c) evaluate, following the latent trait theory, whether the items of both ESS and RSS could be conceptualized as different levels of an interval variable representative of a single latent trait related to sleep propensity.
Methods: One hundred and forty-six inpatients suffering from different sleep disorders filled in both the RSS and ESS in a sleep disorder centre.
Results: Indexes of fit derived by the application of the extended logistic model are consistent with the idea that each ESS item can be conceptualized as different levels of an interval variable representative of a single latent trait. However, most of the ESS items are found to be located at the opposite extremes of this continuum.
Conclusions: The under representation of situations characterized by an intermediate soporific nature in the ESS could limit ESS sensitivity to detect intermediate variations of sleep propensity.
The Arabidopsis gene COI1 is required for jasmonic acid (JA)-induced growth inhibition, resistance to insect herbivory, and resistance to pathogens. In addition, COI1 is also required for ...transcription of several genes induced by wounding or by JA. Here, we use microarray gene transcription profiling of wild type and coi1 mutant plants to examine the extent of the requirement of COI1 for JA-induced and wound-induced gene transcription. We show that COI1 is required for expression of approximately 84% of 212 genes induced by JA, and for expression of approximately 44% of 153 genes induced by wounding. Surprisingly, COI1 was also required for repression of 53% of 104 genes whose expression was suppressed by JA, and for repression of approximately 46% of 83 genes whose expression was suppressed by wounding. These results indicate that COI1 plays a pivotal role in wound- and JA signalling.
The polymorphic barley (Hordeum vulgare) Mla locus harbors allelic race-specific resistance (R) genes to the powdery mildew fungus Blumeria graminis f sp hordei. The highly sequence-related MLA ...proteins contain an N-terminal coiled-coil structure, a central nucleotide binding (NB) site, a Leu-rich repeat (LRR) region, and a C-terminal non-LRR region. Using transgenic barley lines expressing epitope-tagged MLA1 and MLA6 derivatives driven by native regulatory sequences, we show a reversible and salt concentration-dependent distribution of the intracellular MLA proteins in soluble and membrane-associated pools. A posttranscriptional process directs fourfold greater accumulation of MLA1 over MLA6. Unexpectedly, in rar1 mutant plants that are compromised for MLA6 but not MLA1 resistance, the steady state level of both MLA isoforms is reduced. Furthermore, differential steady state levels of MLA1/MLA6 hybrid proteins correlate with their requirement for RAR1; the RAR1-independent hybrid protein accumulates to higher levels and the RAR1-dependent one to lower levels. Interestingly, yeast two-hybrid studies reveal that the LRR domains of RAR1-independent but not RAR1-dependent MLA isoforms interact with SGT1, a RAR1 interacting protein required for the function of many NB-LRR type R proteins. Our findings implicate the existence of a conserved mechanism to reach minimal NB-LRR R protein thresholds that are needed to trigger effective resistance responses.
Ubiquitination is emerging as a common regulatory mechanism that controls a range of cellular processes in plants. Recent exciting discoveries from several laboratories suggest that ubiquitination ...may also play an important role in plant disease resistance. Several putative ubiquitin ligases have been identified as defence regulators. In addition, a combination of genetic screens and gene-silencing technologies has identified subunits and proposed regulators of SCF ubiquitin ligases as essential components of resistance (
R)-gene-mediated resistance. Although no ubiquitin ligase targets that are associated with disease resistance have yet been identified in plants, there is evidence that this well-known protein-modification system may regulate plant defences against pathogens.
Summary
Jasmonates (JAs) regulate Arabidopsis thaliana wound and defence responses, pollen development, and stress‐related growth inhibition. Significantly, each of these responses requires COI1, an ...F‐box protein. Other F‐box proteins interact with SKP1 and cullin proteins to form SCF complexes that selectively recruit regulatory proteins targeted for ubiquitination. To determine whether COI1 also functions in an SCF complex, we have characterized Arabidopsis proteins that bind to COI1. An Arabidopsis cDNA expression library was screened in yeast for clones that produce proteins which can bind to COI1. We recovered two SKP1 homologues and a histone deacetylase. The Arabidopsis F‐box protein TIR1 interacted with SKP1 proteins, but not with the histone deacetylase. Mutant COI1 proteins revealed that the F‐box is required for interaction with SKP1s, but that sequences in leucine‐rich repeat domains are required for interaction with the histone deacetylase. Epitope‐tagged COI1 was introduced into Arabidopsis plants and cell cultures. Co‐immunoprecipitation experiments confirmed the interaction in planta of COI1 with SKP1‐like proteins and histone deacetylase, and also indicated that COI1 interacted with cullin. These results suggest that COI1 forms an SCFCOI1 complex in vivo. COI1 is therefore expected to form a functional E3‐type ubiquitin ligase in plants and to regulate expression of jasmonate responsive genes, possibly by targeted ubiquitination of a histone deacetylase.
The powdery mildew resistance genes RPW8.1 and RPW8.2 from Arabidopsis differ from the other isolated plant resistance (R) genes in their predicted protein domains and their resistance spectrum. The ...two homologous RPW8 genes encode small proteins featuring a predicted amino-terminal transmembrane anchor domain and a coiled-coil domain and confer resistance to a broad spectrum of powdery mildews. Here, we show that Arabidopsis plants expressing the RPW8 genes have enhanced resistance to another biotrophic pathogen, Hyaloperonospora parasitica, raising the possibility that the RPW8 genes may function to enhance salicylic-acid-dependent basal defenses, rather than as powdery-mildew-specific R genes. When overexpressed from their native promoters, the RPW8 genes confer enhanced resistance to the Cauliflower mosaic virus, but render plants more susceptible to the necrotrophic fungal pathogens Alternaria and Botrytis spp. Furthermore, we show that the RPW8 proteins appear to be localized to the endomembrane system, overlapping with the endoplasmic reticulum-associated small GTPase SAR1, and accumulate to higher levels in response to application of exogenous salicylic acid, one of the signaling molecules of plant defense.
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