Rapid and dynamic subcellular reorganization following mechanical stimulation of Arabidopsis epidermal cells mimics responses to fungal and oomycete attack

<p>Abstract</p> <p>Background</p> <p>Plant cells respond to the presence of potential fungal or oomycete pathogens by mounting a basal defence response that involves aggregation of cytoplasm, reorganization of cytoskeletal, endomembrane and other cell components and development of cell wall appositions beneath the infection site. This response is induced by non-adapted, avirulent and virulent pathogens alike, and in the majority of cases achieves penetration resistance against the microorganism on the plant surface. To explore the nature of signals that trigger this subcellular response and to determine the timing of its induction, we have monitored the reorganization of GFP-tagged actin, microtubules, endoplasmic reticulum (ER) and peroxisomes in <it>Arabidopsis </it>plants – after touching the epidermal surface with a microneedle.</p> <p>Results</p> <p>Within 3 to 5 minutes of touching the surface of <it>Arabidopsis </it>cotyledon epidermal cells with fine glass or tungsten needles, actin microfilaments, ER and peroxisomes began to accumulate beneath the point of contact with the needle. Formation of a dense patch of actin was followed by focusing of actin cables on the site of contact. Touching the cell surface induced localized depolymerization of microtubules to form a microtubule-depleted zone surrounding a dense patch of GFP-tubulin beneath the needle tip. The concentration of actin, GFP-tubulin, ER and peroxisomes remained focused on the contact site as the needle moved across the cell surface and quickly dispersed when the needle was removed.</p> <p>Conclusion</p> <p>Our results show that plant cells can detect the gentle pressure of a microneedle on the epidermal cell surface and respond by reorganizing subcellular components in a manner similar to that induced during attack by potential fungal or oomycete pathogens. The results of our study indicate that during plant-pathogen interactions, the basal defence response may be induced by the plant's perception of the physical force exerted by the pathogen as it attempts to invade the epidermal cell surface.</p

MicroR159 regulation of most conserved targets in Arabidopsis has negligible phenotypic effects

BACKGROUND A current challenge of microRNA (miRNA) research is the identification of biologically relevant miRNA:target gene relationships. In plants, high miRNA:target gene complementarity has enabled accurate target predictions, and slicing of target mRNAs has facilitated target validation through rapid amplification of 5' cDNA ends (5'-RACE) analysis. Together, these approaches have identified more than 20 targets potentially regulated by the deeply conserved miR159 family in Arabidopsis, including eight MYB genes with highly conserved miR159 target sites. However, genetic analysis has revealed the functional specificity of the major family members, miR159a and miR159b is limited to only two targets, MYB33 and MYB65. Here, we examine the functional role of miR159 regulation for the other potential MYB target genes. RESULTS For these target genes, functional analysis failed to identify miR159 regulation that resulted in any major phenotypic impact, either at the morphological or molecular level. This appears to be mainly due to the quiescent nature of the remaining family member, MIR159c. Although its expression overlaps in a temporal and spatial cell-specific manner with a subset of these targets in anthers, the abundance of miR159c is extremely low and concomitantly a mir159c mutant displays no anther defects. Examination of potential miR159c targets with conserved miR159 binding sites found neither their spatial or temporal expression domains appeared miR159 regulated, despite the detection of miR159-guided cleavage products by 5'-RACE. Moreover, expression of a miR159-resistant target (mMYB101) resulted predominantly in plants that are indistinguishable from wild type. Plants that displayed altered morphological phenotypes were found to be ectopically expressing the mMYB101 transgene, and hence were misrepresentative of the in vivo functional role of miR159. CONCLUSIONS This study presents a novel explanation for a paradox common to plant and animal miRNA systems, where among many potential miRNA-target relationships usually only a few appear physiologically relevant. The identification of a quiescent miR159c:target gene regulatory module in anthers provides a likely rationale for the presence of conserved miR159 binding sites in many targets for which miR159 regulation has no obvious functional role. Remnants from the demise of such modules may lead to an overestimation of miRNA regulatory complexity when investigated using bioinformatic, 5'-RACE or transgenic approaches.RSA was funded by an ANU postgraduate scholarship and by a CSIRO Emerging Science Initiative. JL is the recipient of an ANU international student postgraduate scholarship. This research was supported by an Australian Research Council grant DP0773270

An Online Educational Program Improves Pediatric Oncology Nurses’ Knowledge, Attitudes, and Spiritual Care Competence

This study evaluated the potential impact of an online spiritual care educational program on pediatric nurses’ attitudes toward and knowledge of spiritual care and their competence to provide spiritual care to children with cancer at the end of life. It was hypothesized that the intervention would increase nurses’ positive attitudes toward and knowledge of spiritual care and increase nurses’ level of perceived spiritual care competence. A positive correlation was expected between change in nurses’ perceived attitudes toward and knowledge of spiritual care and change in nurses’ perceived spiritual care competence. A prospective, longitudinal design was employed, and analyses included one-way repeated-measures analysis of variance, linear regression, and partial correlation. Statistically significant differences were found in nurses’ attitudes toward and knowledge of spiritual care and nurses’ perceived spiritual care competence. There was a positive relationship between change scores in nurses’ attitudes toward and knowledge of spiritual care and nurses’ spiritual care competence. Online spiritual care educational programs may exert a lasting impact on nurses’ attitudes toward and knowledge of spiritual care and their competence to provide spiritual care to children with cancer at the end of life. Additional studies are required to evaluate the direct effects of educational interventions patient outcomes

Nodulating Legumes Are Distinguished by a Sensitivity to Cytokinin in the Root Cortex Leading to Pseudonodule Development

Root nodule symbiosis (RNS) is a feature confined to a single clade of plants, the Fabids. Among Fabids capable of RNS, legumes form root cortex-based nodules in symbioses with rhizobia, while actinorhizal species form lateral root-based nodules with actinomycetes. Cytokinin has previously been shown to be sufficient for “pseudonodule” initiation in model legumes. Here, we tested whether this response correlates with the ability to nodulate across a range of plant species. We analyzed the formation of pseudonodules in 17 nodulating and non-nodulating legume species, and 11 non-legumes, including nodulating actinorhizal species, using light and fluorescence microscopy. Cytokinin-induced pseudonodules arising from cortical cell divisions occurred in all nodulating legume species, but not in any of the other species, including non-nodulating legumes. Pseudonodule formation was dependent on the CRE1 cytokinin receptor in Medicago truncatula. Inhibition of root growth by cytokinin occurred across plant groups, indicating that pseudonodule development is the result of a specific cortical cytokinin response unique to nodulating legumes. Lack of a cortical cytokinin response from the Arabidopsis thaliana cytokinin reporter TCSn::GFP supported this hypothesis. Our results suggest that the ability to form cortical cell-derived nodules was gained in nodulating legumes, and likely lost in non-nodulating legumes, due to a specific root cortical response to cytokinin

The Extreme Outer Regions of Disk Galaxies: I. Chemical Abundances of HII Regions

We present the first results of an ongoing project to investigate the present-day chemical abundances of the extreme outer parts of galactic disks, as probed by the emission line spectra of a new sample of HII regions. The galaxies studied here, NGC628, NGC1058 and NGC6946, are all late-type spiral galaxies, characterized by larger than average HI-to-optical sizes. Our deep Halpha images have revealed the existence of recent massive star formation, traced by HII regions, out to, and beyond, two optical radii in these galaxies (defined by the B-band 25th magnitude isophote). Optical spectra of these newly-discovered HII regions are used to investigate their densities, ionization parameters, extinctions and in particular their oxygen and nitrogen abundances. Our measurements reveal gas-phase abundances of O/H~10-15% of the solar value, and N/O~20-25% of the solar value, at radii of 1.5-2 R25. Clear evidence also exists for diminished dust extinction (Av~0-0.2) at large radii. The combination of our measurements of outer disk HII region abundances with those for inner disk HII regions published in the literature is a powerful probe of the shape of abundance gradients over unprecedented radial baselines. Within the limits of the current dataset, the radial abundance variations are consistent with single log-linear relationships, although the derived slopes can often differ considerably from those found if only inner disk HII regions are used to define the fit. Interestingly, both the mean level of enrichment and the ratio of N/O measured in extreme outer galactic disks are similar to those values measured in some high redshift damped Lyman-alpha absorbers, suggesting that outer disks at the present epoch are relatively unevolved. (abridged)Comment: 36 pages, 10 embedded postscript files, 3 jpeg files, 7 postscript tables; accepted for publication in the Astronomical Journal (August issue

Late-acting dominant lethal genetic systems and mosquito control

BACKGROUND: Reduction or elimination of vector populations will tend to reduce or eliminate transmission of vector-borne diseases. One potential method for environmentally-friendly, species-specific population control is the Sterile Insect Technique (SIT). SIT has not been widely used against insect disease vectors such as mosquitoes, in part because of various practical difficulties in rearing, sterilization and distribution. Additionally, vector populations with strong density-dependent effects will tend to be resistant to SIT-based control as the population-reducing effect of induced sterility will tend to be offset by reduced density-dependent mortality. RESULTS: We investigated by mathematical modeling the effect of manipulating the stage of development at which death occurs (lethal phase) in an SIT program against a density-dependence-limited insect population. We found late-acting lethality to be considerably more effective than early-acting lethality. No such strains of a vector insect have been described, so as a proof-of-principle we constructed a strain of the principal vector of the dengue and yellow fever viruses, Aedes (Stegomyia) aegypti, with the necessary properties of dominant, repressible, highly penetrant, late-acting lethality. CONCLUSION: Conventional SIT induces early-acting (embryonic) lethality, but genetic methods potentially allow the lethal phase to be tailored to the program. For insects with strong density-dependence, we show that lethality after the density-dependent phase would be a considerable improvement over conventional methods. For density-dependent parameters estimated from field data for Aedes aegypti, the critical release ratio for population elimination is modeled to be 27% to 540% greater for early-acting rather than late-acting lethality. Our success in developing a mosquito strain with the key features that the modeling indicated were desirable demonstrates the feasibility of this approach for improved SIT for disease control

Galaxy Populations and Evolution in Clusters III. The Origin of Low-Mass Galaxies in Clusters: Constraints from Stellar Populations

Low-mass galaxies in nearby clusters are the most numerous galaxy type in the universe, yet their origin and properties remain largely unknown. To study basic questions concerning these galaxies we present the results of a survey designed to constrain the characteristics and properties of the stellar populations in a magnitude complete sample of low-mass cluster galaxies (LMCGs) in the center of the Perseus cluster. Using deep, high-quality WIYN UBR images, we demonstrate that the 53 LMCGs in our sample have a significant scatter about the color-magnitude relationship at M_B > -15. By comparing single-burst stellar population models to our photometry, we argue that stellar populations in LMCGs all have ages > 1 Gyrs, with redder LMCGs having stellar metallicities [Fe/H] > -0.5. By assuming that the colors of LMCGs reflect metallicity, and have co-evolved with the giant ellipticals, we find a wide range of values, from solar to [Fe/H] ~ -3. We argue from this that LMCGs have multiple origins, and fundamentally differ from Local Group dwarf spheroidals/ellipticals. The inferred lower metallicities of the bluer LMCGs implies that these are possibly primordial galaxies formed through self enrichment and stellar feedback provided by winds from supernova. We also investigate several other formation scenarios for these LMCGS, including: self enrichment induced by the confinement of metals in halos by the intracluster medium, in situ formation out of intracluster gas, systems with extreme dark halos, and as remnants of higher mass systems. We conclude that roughly half of all low-mass cluster galaxies have stellar populations and kinematic properties, discussed in previous papers in this series, consistent with being the remnants of stripped galaxies accreted into clusters a few Gyrs ago.Comment: Accepted to the Astronomical Journal, 35 pages. For full resolution images of the cluster LMCGs and other figures, please download the version at http://www.astro.caltech.edu/~cc/gpec3.p

Aspergillus polymerase chain reaction: systematic review of evidence for clinical use in comparison with antigen testing

Background. Aspergillus polymerase chain reaction (PCR) was excluded from the European Organisation for the Research and Treatment of Cancer/Mycoses Study Group (EORTC/MSG) definitions of invasive fungal disease because of limited standardization and validation. The definitions are being revised. Methods. A systematic literature review was performed to identify analytical and clinical information available on inclusion of galactomannan enzyme immunoassay (GM-EIA) (2002) and β-D-glucan (2008), providing a minimal threshold when considering PCR. Categorical parameters and statistical performance were compared. Results. When incorporated, GM-EIA and β-D-glucan sensitivities and specificities for diagnosing invasive aspergillosis were 81.6% and 91.6%, and 76.9% and 89.4%, respectively. Aspergillus PCR has similar sensitivity and specificity (76.8%–88.0% and 75.0%–94.5%, respectively) and comparable utility. Methodological recommendations and commercial PCR assays assist standardization. Although all tests have limitations, currently, PCR is the only test with independent quality control. Conclusions. We propose that there is sufficient evidence that is at least equivalent to that used to include GM-EIA and β-D-glucan testing, and that PCR is now mature enough for inclusion in the EORTC/MSG definitions

Multi-centre parallel arm randomised controlled trial to assess the effectiveness and cost-effectiveness of a group-based cognitive behavioural approach to managing fatigue in people with multiple sclerosis

Abstract (provisional) Background Fatigue is one of the most commonly reported and debilitating symptoms of multiple sclerosis (MS); approximately two-thirds of people with MS consider it to be one of their three most troubling symptoms. It may limit or prevent participation in everyday activities, work, leisure, and social pursuits, reduce psychological well-being and is one of the key precipitants of early retirement. Energy effectiveness approaches have been shown to be effective in reducing MS-fatigue, increasing self-efficacy and improving quality of life. Cognitive behavioural approaches have been found to be effective for managing fatigue in other conditions, such as chronic fatigue syndrome, and more recently, in MS. The aim of this pragmatic trial is to evaluate the clinical and cost-effectiveness of a recently developed group-based fatigue management intervention (that blends cognitive behavioural and energy effectiveness approaches) compared with current local practice. Methods This is a multi-centre parallel arm block-randomised controlled trial (RCT) of a six session group-based fatigue management intervention, delivered by health professionals, compared with current local practice. 180 consenting adults with a confirmed diagnosis of MS and significant fatigue levels, recruited via secondary/primary care or newsletters/websites, will be randomised to receive the fatigue management intervention or current local practice. An economic evaluation will be undertaken alongside the trial. Primary outcomes are fatigue severity, self-efficacy and disease-specific quality of life. Secondary outcomes include fatigue impact, general quality of life, mood, activity patterns, and cost-effectiveness. Outcomes in those receiving the fatigue management intervention will be measured 1 week prior to, and 1, 4, and 12 months after the intervention (and at equivalent times in those receiving current local practice). A qualitative component will examine what aspects of the fatigue management intervention participants found helpful/unhelpful and barriers to change. Discussion This trial is the fourth stage of a research programme that has followed the Medical Research Council guidance for developing and evaluating complex interventions. What makes the intervention unique is that it blends cognitive behavioural and energy effectiveness approaches. A potential strength of the intervention is that it could be integrated into existing service delivery models as it has been designed to be delivered by staff already working with people with MS. Service users will be involved throughout this research. Trial registration: Current Controlled Trials ISRCTN7651747