Neighbourhood Characteristics and Long-Term Air Pollution Levels Modify the Association between the Short-Term Nitrogen Dioxide Concentrations and All-Cause Mortality in Paris

BackgroundWhile a great number of papers have been published on the short-term effects of air pollution on mortality, few have tried to assess whether this association varies according to the neighbourhood socioeconomic level and long-term ambient air concentrations measured at the place of residence. We explored the effect modification of 1) socioeconomic status, 2) long-term NO₂ ambient air concentrations, and 3) both combined, on the association between short-term exposure to NO₂ and all-cause mortality in Paris (France).MethodsA time-stratified case-crossover analysis was performed to evaluate the effect of short-term NO₂ variations on mortality, based on 79,107 deaths having occurred among subjects aged over 35 years, from 2004 to 2009, in the city of Paris. Simple and double interactions were statistically tested in order to analyse effect modification by neighbourhood characteristics on the association between mortality and short-term NO₂ exposure. The data was estimated at the census block scale (n=866).ResultsThe mean of the NO₂ concentrations during the five days prior to deaths were associated with an increased risk of all-cause mortality: overall Excess Risk (ER) was 0.94% (95%CI=[0.08;1.80]. A higher risk was revealed for subjects living in the most deprived census blocks in comparison with higher socioeconomic level areas (ER=3.14% (95%CI=[1.41-4.90], p<0.001). Among these deprived census blocks, excess risk was even higher where long-term average NO₂ concentrations were above 55.8 μg/m³ (the top tercile of distribution): ER=4.84% (95%CI=[1.56;8.24], p for interaction=0.02).ConclusionOur results show that people living in census blocks characterized by low socioeconomic status are more vulnerable to air pollution episodes. There is also an indication that people living in these disadvantaged census blocks might experience even higher risk following short-term air pollution episodes, when they are also chronically exposed to higher NO₂ levels.     

CLASP2-dependent microtubule capture at the neuromuscular junction membrane requires LL5β and actin for focal delivery of acetylcholine receptor vesicles

A hallmark of the neuromuscular junction (NMJ) is the high density of acetylcholine receptors (AChRs) in the postsynaptic muscle membrane. The postsynaptic apparatus of the NMJ is organized by agrin secreted from motor neurons. The mechanisms that underlie the focal delivery of AChRs to the adult NMJ are not yet understood in detail. We previously showed that microtubule (MT) capture by the plus end–tracking protein CLASP2 regulates AChR density at agrin-induced AChR clusters in cultured myotubes via PI3 kinase acting through GSK3β. Here we show that knockdown of the CLASP2-interaction partner LL5β by RNAi and forced expression of a CLASP2 fragment blocking the CLASP2/LL5β interaction inhibit microtubule capture. The same treatments impair focal vesicle delivery to the clusters. Consistent with these findings, knockdown of LL5β at the NMJ in vivo reduces the density and insertion of AChRs into the postsynaptic membrane. MT capture and focal vesicle delivery to agrin-induced AChR clusters are also inhibited by microtubule- and actin-depolymerizing drugs, invoking both cytoskeletal systems in MT capture and in the fusion of AChR vesicles with the cluster membrane. Combined our data identify a transport system, organized by agrin through PI3 kinase, GSK3β, CLASP2, and LL5β, for precise delivery of AChR vesicles from the subsynaptic nuclei to the overlying synaptic membrane.     

Structure Analysis Uncovers a Highly Diverse but Structurally Conserved Effector Family in Phytopathogenic Fungi

Phytopathogenic ascomycete fungi possess huge effector repertoires that are dominated by hundreds of sequence-unrelated small secreted proteins. The molecular function of these effectors and the evolutionary mechanisms that generate this tremendous number of singleton genes are largely unknown. To get a deeper understanding of fungal effectors, we determined by NMR spectroscopy the 3-dimensional structures of the Magnaporthe oryzae effectors AVR1-CO39 and AVR-Pia. Despite a lack of sequence similarity, both proteins have very similar 6 β-sandwich structures that are stabilized in both cases by a disulfide bridge between 2 conserved cysteins located in similar positions of the proteins. Structural similarity searches revealed that AvrPiz-t, another effector from M. oryzae, and ToxB, an effector of the wheat tan spot pathogen Pyrenophora tritici-repentis have the same structures suggesting the existence of a family of sequence-unrelated but structurally conserved fungal effectors that we named MAX-effectors (M agnaporthe Avrs and ToxB like). Structure-informed pattern searches strengthened this hypothesis by identifying MAX-effector candidates in a broad range of ascomycete phytopathogens. Strong expansion of the MAX-effector family was detected in M. oryzae and M. grisea where they seem to be particularly important since they account for 5–10% of the effector repertoire and 50% of the cloned avirulence effectors. Expression analysis indicated that the majority of M. oryzae MAX-effectors are expressed specifically during early infection suggesting important functions during biotrophic host colonization. We hypothesize that the scenario observed for MAX-effectors can serve as a paradigm for ascomycete effector diversity and that the enormous number of sequence-unrelated ascomycete effectors may in fact belong to a restricted set of structurally conserved effector families.     

早产儿高胆红素血症与肠道菌群的相关性

目的探讨高胆红素血症早产儿与非高胆红素血症早产儿肠道菌群的差异,为该病的治疗提供思路和依据。方法选择2017年1月至6月出生后即在本院新生儿科治疗的早产儿(胎龄35+1～36+6周)为研究对象,其中高胆红素血症早产儿(黄疸组)124例,非高胆红素血症早产儿(对照组)118例。采集两组对象出生后24 h内的首次胎便,采用高通量测序技术对粪便样本中细菌16S rRNA基因进行检测,分析肠道菌群组成情况。结果黄疸组早产儿肠道微生物群落组成与对照组在门水平上相似度较高。在属水平上,两组对象肠道菌群均以Ralstonia、Rhodococcus、Enterococcus为主。对照组患儿肠道Lactobacillus的相对丰度显著高于黄疸组(t=-2.073 0,P=0.039 1)。黄疸组患儿肠道Ralstonia的相对丰度与总胆红素水平呈负相关(r=-0.314 8,P=0.000 3)。结论高胆红素血症早产儿与非高胆红素血症早产儿肠道菌群的种类和丰度存在差异。Lactobacillus可能是高胆红素血症的潜在生物标记物。     

Redox responses of Arabidopsis thaliana to the green peach aphid,Myzus persicae

The green peach aphid (Myzus persicae) is a phloem-feeding insect that causes economic damage on a wide array of crops. Using a luminol-based assay, a superoxide-responsive reporter gene (Zat12::luciferase), and a probe specific to hydrogen peroxide (HyPer), we demonstrated that this aphid induces accumulation of reactive oxygen species (ROS) in Arabidopsis thaliana. Similar to the apoplastic oxidative burst induced by pathogens, this response to aphids was rapid and transient, with two peaks occurring within 1 and 4 hr after infestation. Aphid infestation also induced an oxidative response in the cytosol and peroxisomes, as measured using a redox-sensitive variant of green fluorescent protein (roGFP2). This intracellular response began within minutes of infestation but persisted 20 hr or more after inoculation, and the response of the peroxisomes appeared stronger than the response in the cytosol. Our results suggest that the oxidative response to aphids involves both apoplastic and intracellular sources of ROS, including ROS generation in the peroxisomes, and these different sources of ROS may potentially differ in their impacts on host suitability for aphids.     

Kinetics of Interaction between ADP-ribosylation Factor-1 (Arf1) and the Sec7 Domain of Arno Guanine Nucleotide Exchange Factor,Modulation by Allosteric Factors,and the Uncompetitive Inhibitor Brefeldin A

The GDP/GTP nucleotide exchange of Arf1 is catalyzed by nucleotide exchange factors (GEF), such as Arno, which act through their catalytic Sec7 domain. This exchange is a complex mechanism that undergoes conformational changes and intermediate complex species involving several allosteric partners such as nucleotides, Mg²⁺, and Sec7 domains. Using a surface plasmon resonance approach, we characterized the kinetic binding parameters for various intermediate complexes. We first confirmed that both GDP and GTP counteract equivalently to the free-nucleotide binary Arf1-Arno complex stability and revealed that Mg²⁺ potentiates by a factor of 2 the allosteric effect of GDP. Then we explored the uncompetitive inhibitory mechanism of brefeldin A (BFA) that conducts to an abortive pentameric Arf1-Mg²⁺-GDP-BFA-Sec7 complex. With BFA, the association rate of the abortive complex is drastically reduced by a factor of 42, and by contrast, the 15-fold decrease of the dissociation rate concurs to stabilize the pentameric complex. These specific kinetic signatures have allowed distinguishing the level and nature as well as the fate in real time of formed complexes according to experimental conditions. Thus, we showed that in the presence of GDP, the BFA-resistant Sec7 domain of Arno can also associate to form a pentameric complex, which suggests that the uncompetitive inhibition by BFA and the nucleotide allosteric effect combine to stabilize such abortive complex.     

Genetic variation of horse chestnut and red horse chestnut and trees susceptibility to Erysiphe flexuosa and Cameraria ohridella

Trees of Aesculus sp. are often present in European landscapes. Common horse chestnut and red horse chestnut are seriously damaged by the fungus Erysiphe flexuosa as well as the pest Cameraria ohridella. Both pathogen and pest have spread throughout Europe. A genetic background of trees resistance still remains unknown. The present study was undertaken to estimate genetic variation of A. hippocastanum and A.×carnea grown in urban greens and their susceptibility to powdery mildew and horse chestnut leafminer. According to obtained results both species were infected by E. flexuosa in a similar degree but there were significant differences in susceptibility of particular trees (ANOVA). C. ohridella damaged only A. hippocastanum. The correlation between age of trees and degree of infestation by pathogen and pest was not observed. The significant genetic variability between two Aesculus species was revealed by the analysis of molecular variance (AMOVA) where both the intra- and the inter-species variation were found to be significant. It was shown that 73.0% of the genetic variance was contributed by the differentiation between A. hippocastanum and A.×carnea, whereas 27.0% was partitioned within species. The medium level of genetic diversity of Aesculus spp. was determined using SRAP and RAPD analyses. The mean value of genetic similarity was equal to 0.55 for common horse chestnut and 0.98 for red horse chestnut. Among 40 polymorphic SRAP and RAPD markers 17 were associated with degree of leaf damage caused by C. ohridella.     

Xanthan degragation by biofilm in porous media

Biological activity in oil reservoirs can cause significant problems such as souring and plugging. This study focuses on the problem of polymer degradation and permeability reduction due to biofilm formation during polymer injection for improved oil recovery. Polymers are included in injection fluids to increase their viscosity. Results relating biological processes and polymer degradation to fluid‐dynamic conditions in a laboratory model porous medium are presented.

A transparent flow cell with an etched two‐dimensional network of pores served as a model porous medium. A sterile xanthan polymer and natural sea water solution were continuously injected into the porous medium. A bacterial culture capable of xanthan degradation was introduced into the cell by a single injection. Some of the cells from this culture attached to the pore walls forming an immobile bacterial culture, termed biofilm. The development of this biofilm, its xanthan degradation and its effect on permeability were measured.

The effects of injection rate and rate transitions were analyzed. Injection fluid viscosity was reduced by 30% after 5 min flow through the porous medium at the maximum steady state degradation rate observed. Permeability was significantly reduced by the xanthan degrading biofilm, causing an increase in pressure drop through the porous medium of up to 80%. Polymer injection in oil reservoirs may, therefore, have negative effects on oil recovery, unless efficient biofouling control is applied. The methodology presented may serve as a tool in the development of biofouling control measures in porous media.     

Photosystem II antenna complexes CP26 and CP29 are essential for nonphotochemical quenching in Chlamydomonas reinhardtii

Photosystems must balance between light harvesting to fuel the photosynthetic process for CO₂ fixation and mitigating the risk of photodamage due to absorption of light energy in excess. Eukaryotic photosynthetic organisms evolved an array of pigment-binding proteins called light harvesting complexes constituting the external antenna system in the photosystems, where both light harvesting and activation of photoprotective mechanisms occur. In this work, the balancing role of CP29 and CP26 photosystem II antenna subunits was investigated in Chlamydomonas reinhardtii using CRISPR-Cas9 technology to obtain single and double mutants depleted of monomeric antennas. Absence of CP26 and CP29 impaired both photosynthetic efficiency and photoprotection: Excitation energy transfer from external antenna to reaction centre was reduced, and state transitions were completely impaired. Moreover, differently from higher plants, photosystem II monomeric antenna proteins resulted to be essential for photoprotective thermal dissipation of excitation energy by nonphotochemical quenching.     

Root plasticity maintains growth of temperate grassland species under pulsed water supply

Background and aims

The frequency of rain is predicted to change in high latitude areas with more precipitation in heavy, intense events interspersed by longer dry periods. These changes will modify soil drying cycles with unknown consequences for plant performance of temperate species.

Methods

We studied plant growth and root traits of juveniles of four grasses and four dicots growing in a greenhouse, when supplying the same total amount of water given either regular every other day or pulsed once a week.

Results

Pulsed water supply replenished soil moisture immediately after watering, but caused substantial drought stress at the end of the watering cycle, whereas regular watering caused more moderate but consistent drought. Grasses had lower water use efficiency in the pulsed watering compared to regular watering, whereas dicots showed no difference. Both grasses and dicots developed thinner roots, thus higher specific root length, and greater root length in the pulsed watering. Growth of dicots was slightly increased under pulsed watering.

Conclusions

Temperate species coped with pulsed water supply by eliciting two responses: i) persistent shoot growth, most likely by maximizing growth at peaks of soil moisture, thus compensating for slower growth during drought periods; ii) plasticity of root traits related to increased resource uptake. Both responses likely account for subtle improvement of growth under changed water supply conditions.