TRP-2 specifically decreases WM35 cell sensitivity to oxidative stress

TRP-2 (dopachrome tautomerase) is a melanogenic enzyme whose expression was recently reported to modulate melanocyte response to different cytotoxic events. Here we studied a possible role of TRP-2 in the oxidative stress response in the amelanotic WM35 melanoma cell line. Cell viability assays showed that TRP-2 overexpression in WM35 cells reduced their sensitivity to oxidative stress. Comet assays linked TRP-2 expression to DNA damage protection, and high-performance liquid chromotography-tandem mass spectrometry experiments showed an increase in intracellular glutathione in TRP-2-overexpressing cells. These effects were specifically reversed when TRP-2 was silenced by RNA interference. Nevertheless, these properties appeared to depend on a particular cell environment because expression of TRP-2 failed to rescue HEK epithelial cells exposed to similar treatments.     

Mating system, sexual dimorphism, and the opportunity for sexual selection in a territorial ungulate

In mammals, species with high sexual size dimorphism tend tohave highly polygynous mating systems associated with high variancein male lifetime reproductive success (LRS), leading to a highopportunity for sexual selection. However, little informationis available for species with weak sexual size dimorphism. Ina long-term study population, we used parentage analysis basedon 21 microsatellite markers to describe, for the first time,variance in male lifetime breeding success (LBS) of roe deer,a territorial ungulate where males weigh less than 10% morethan females. LBS ranged from 0 to 14 (mean = 4.54, variance= 15.5), and its distribution was highly skewed, with only afew males obtaining high LBS and many males failing to breedor siring only one fawn. As predicted for polygynous specieswith low sexual size dimorphism, the standardized variance inmale LBS was low (I_m = 0.75) and was only slightly higher thanthe standardized variance in female LRS (I_f = 0.53), suggestinga low opportunity for sexual selection. The I_m value reportedhere for roe deer is much lower than values reported for highlydimorphic ungulates such as red deer (I_m > 3). We suggestthat, along a continuum of opportunity for sexual selection,roe deer occupy a position closer to monogamous and monomorphicterritorial ungulates than to highly polygynous, sexually dimorphicungulates with dominance rank–based mating systems suchas harems or roving mating systems.     

Assessment of local predation risk: the role of subthreshold concentrations of chemical alarm cues

The ability to accurately assess local predation risk is criticalto prey individuals, as it allows them to maximize threat-sensitivetrade-offs between predator avoidance and other fitness relatedactivities. A wide range of taxonomically diverse prey (includingmany freshwater fishes) relies on chemical alarm cues (alarmpheromones) as their primary information source for local riskassessment. However, the value of chemical alarm cues has beenquestioned due to the availability of additional sensory inputs(i.e., visual cues) and the lack of an overt antipredator responseunder conditions of low perceived risk. In this paper, we testthe hypothesis that chemical alarm cues at concentrations belowthe point at which they elicit an overt behavioral responsefunction to increase vigilance towards other sensory modalities(i.e., visual alarm cues). Shoals of glowlight tetras (Hemigrammuserythrozonus) exposed to the subthreshold concentration of hypoxanthine-3-N-oxide(the putative Ostariophysan alarm pheromone) did not exhibitan overt antipredator response in the absence of secondary visualcues (not different than the distilled water control). However,when exposed to the sight of a visually alarmed conspecific,they significantly increased the intensity of their antipredatorresponse (not different from shoals exposed to the suprathresholdalarm cue). This study demonstrates that prey may benefit fromresponding to low concentration alarm cues by increasing vigilancetowards secondary cues during local risk assessment, even inthe absence of an overt behavioral response. By increasing vigilancetowards secondary risk assessment cues in the presence of alow risk chemical cue, individuals are likely able to maximizethe threat-sensitive trade-offs between predator avoidance andother fitness related activities.     

Molecular cross talk between Toxoplasma gondii and the host immune system

Toxoplasma gondii is an intracellular parasite that frequently infects a large spectrum of warm-blooded animals. This parasite induces abortion and establishes both chronic and silent infections, particularly in the brain. The chronic infection is therefore a permanent threat for the host in cases of immunosuppression. Parasite penetration into the host activates a strong anti-parasite immune response, but is also used by the parasite to chronically persist. In the present paper, we discuss the data obtained in the laboratory of John Boothroyd that reports the molecular cross talk between the parasite rhoptry proteins and the host cell. During host cell invasion, rhoptries participate to the constitution of the mobile junction that drives the parasite into the host cell, while building the parasitophorus vacuole in which the parasite grows. Some soluble rhoptries, such as ROP16, are shed into the cytoplasm, and then reach the nucleus where they can eventually impact different signaling pathways such as STAT3/6, key molecules in the immune response establishment.     

Does the Structure–Function Model GREENLAB Deal with Crop Phenotypic Plasticity Induced by Plant Spacing? A Case Study on Tomato

BACKGROUND AND AIMS: Plant growth models able to simulate phenotypic plasticity are increasingly required because (1) they should enable better predictions of the observed variations in crop production, yield and quality, and (2) their parameters are expected to have a more robust genetic basis, with possible implications for selection of quantitative traits such as growth- and allocation-related processes. The structure-function plant model, GREENLAB, simulates resource-dependent plasticity of plant architecture. Evidence for its generality has been previously reported, but always for plants grown in a limited range of environments. This paper aims to test the model concept to its limits by using plant spacing as a means to generate a gradient of competition for light, and by using a new crop species, tomato, known to exhibit a strong photomorphogenetic response. METHODS: A greenhouse experiment was carried out with three homogeneous planting densities (plant spacing = 0.3, 0.6 and 1 m). Detailed records of plant development, plant architecture and organ growth were made throughout the growing period. Model calibration was performed for each situation using a statistical optimization procedure (multi-fitting). KEY RESULTS AND CONCLUSIONS: Obvious limitations of the present version of the model appeared to account fully for the plant plasticity induced by inter-plant competition for light. A lack of stability was identified for some model parameters at very high planting density. In particular, those parameters characterizing organ sink strengths and governing light interception proved to be environment-dependent. Remarkably, however, responses of the parameter values concerned were consistent with actual growth measurements and with previously reported results. Furthermore, modifications of total biomass production and of allocation patterns induced by the planting-density treatments were accurately simulated using the sets of optimized parameters. These results demonstrate that the overall model structure is potentially able to reproduce the observed plant plasticity and suggest that sound biologically based adaptations could overcome the present model limitations. Potential options for model improvement are proposed, and the possibility of using the kernel algorithm currently available as a fitting tool to build up more sophisticated model versions is advocated.     

Stress and demographic decline: a potential effect mediated by impairment of reproduction and immune function in cyclic vole populations

The stress response is initially adaptive, operating to maintain homeostasis. However, chronic long-term exposure to stressors may have detrimental effects. We proposed that chronic stress may be a major factor in demographic vole cycles, inducing decline in high-density populations. We monitored four populations of the fossorial water vole Arvicola scherman, which undergo pluriannual demographic cycles in the Jura Mountains (France). Sampling was conducted during the high densities and the decline. We measured fecal corticosterone metabolites (FCMs) to assess stress levels and injected phytohemagglutinin to estimate the cell-mediated immune response. We demonstrated that stress levels increase between the high densities and the decline in most of the vole populations. At the individual level, FCM concentrations varied with reproductive status and body condition. During the outbreak, we observed significantly higher levels of FCM concentrations in nulliparous females than in females that had previously reproduced. Moreover, a significant negative correlation was observed between concentrations of FCMs and both immunocompetence and body condition during population decline. These results might reflect an impairment of the female reproductive capability in high densities and accelerated senescence affecting immune function during decline, both arising from chronic stress.     

Next generation of elevated [CO2] experiments with crops: a critical investment for feeding the future world

A rising global population and demand for protein-rich diets are increasing pressure to maximize agricultural productivity. Rising atmospheric [CO₂] is altering global temperature and precipitation patterns, which challenges agricultural productivity. While rising [CO₂] provides a unique opportunity to increase the productivity of C₃ crops, average yield stimulation observed to date is well below potential gains. Thus, there is room for improving productivity. However, only a fraction of available germplasm of crops has been tested for CO₂ responsiveness. Yield is a complex phenotypic trait determined by the interactions of a genotype with the environment. Selection of promising genotypes and characterization of response mechanisms will only be effective if crop improvement and systems biology approaches are closely linked to production environments, that is, on the farm within major growing regions. Free air CO₂ enrichment (FACE) experiments can provide the platform upon which to conduct genetic screening and elucidate the inheritance and mechanisms that underlie genotypic differences in productivity under elevated [CO₂]. We propose a new generation of large-scale, low-cost per unit area FACE experiments to identify the most CO₂-responsive genotypes and provide starting lines for future breeding programmes. This is necessary if we are to realize the potential for yield gains in the future.     

Optimization of Surface Plasmon Resonance Biosensor with Ag/Au Multilayer Structure and Fiber-Optic Miniaturization

In this paper, we report a novel wavelength interrogation-based surface plasmon resonance (SPR) system, in which a film of three Ag layers and three Au layers are alternately deposited on a Kretschmann configuration as sensing element. This multilayer film shows higher sensitivity for refractive index (RI) measurement by comparing with single Au layer structure, which is consistent with its theoretical calculation. A sensitivity range of 2056–5893 nm/RIU can be achieved, which is comparable to RI sensitivities of other wavelength-modulated SPR sensors. Compared with Ag film, this Ag/Au multilayer arrangement offers anti-oxidant protection. This SPR biosensor based on a cost-effective Ag/Au multilayer structure is applicable to the real-time detection of specific interactions and dissociation of low protein concentrations. To extend the application of this highly-sensitive metal film device, we integrated this concept on an optical fiber. The range of RI sensitivities with Ag/Au multilayer was 1847–3309 nm/RIU. This miniaturized Ag/Au multilayer-based fiber optic sensor has a broad application in chemical and biological sensing.     

PSTPIP is a substrate of PTP-PEST and serves as a scaffold guiding PTP-PEST toward a specific dephosphorylation of WASP.

PSTPIP is a tyrosine-phosphorylated protein involved in the organization of the cytoskeleton. Its ectopic expression induces filipodial-like membrane extensions in NIH 3T3 cells. We previously observed a defect in cytokinesis and an increase in the tyrosine phosphorylation of PSTPIP in PTP-PEST-deficient fibroblasts. In this article, we demonstrate that PTP-PEST and PSTPIP are found in the same complexes in vivo and that they interact directly through the CTH domain of PTP-PEST and the coiled-coil domain of PSTPIP. We tested pathways that could regulate the tyrosine phosphorylation of PSTPIP. We found that the activation of the epidermal growth factor and platelet-derived growth factor receptors can induce PSTPIP phosphorylation. With the use of the PP2 inhibitor, we demonstrate that Src kinases are not involved in the epidermal growth factor-mediated phosphorylation of PSTPIP. Together with previous results, this suggests that c-Abl is the critical tyrosine kinase downstream of growth factor receptors responsible for PSTPIP phosphorylation. We also demonstrate that PTP-PEST dephosphorylates PSTPIP at tyrosine 344. Importantly, we identified tyrosine 344 as the main phosphorylation site of PSTPIP by performing tryptic phosphopeptide maps. This is an important finding since tyrosine 367 of PSTPIP was also proposed as a candidate phosphorylation site involved in the negative regulation of the association between PSTPIP and WASP. In this respect, we observed that the PSTPIP.WASP complex is stable in vivo and is not affected by the phosphorylation of PSTPIP. Furthermore, we demonstrate that PSTPIP serves as a scaffold protein between PTP-PEST and WASP and allows PTP-PEST to dephosphorylate WASP. This finding suggests a possible mechanism for PTP-PEST to directly modulate actin remodeling through the PSTPIP-WASP interaction.     

Nitrogen uptake by size-fractionated plankton in permanently well-mixed temperate coastal waters

Nitrogen uptake by net- (15–200 µm), nano- (1–15µm) and picoplankton (<1 µm) was measured overseasonal cycles at two stations with different patterns of biologicaland chemical cycles in the Morlaix Bay (western English Channel).Though assimilable dissolved N nutrient pool at both stationswas nitrate-dominated, characteristics of biomass and N uptakeby netplankton differed from conventional patterns in two respects.In the first, biomass (26–30%) and N uptake (36–43%)were less important than those of nanoplankton. In the second,the netplankton did not show any marked preference for nitrateover ammonium (nitrate to ammonium uptake ratios of 0.98 and1.08). In contrast, nanoplankton had a preference for ammoniumover nitrate (ammonium to nitrate uptake ratios of 2 and 1.2).N uptake by picoplankton was only 8% of total N uptake at bothstations and was supported mainly by regenerated N (66% ammoniumand 17% urea), with nitrate uptake detectable in only one instanceand nitrite uptake in none. Substrate-dependent uptake of ammoniumin all fractions and a higher ammonium uptake in the nanoplanktonfraction in summer at both stations when ambient ammonium concentrationswere high indicated that while nitrate may satisfy a part ofN requirements, availability of ammonium and its flux throughnanoplankton determine the magnitude of total N uptake in thesewaters. Most of the N uptake in picoplankton appears to be autotrophic,suggesting that a substantial part of heterotrophic uptake,if any, could be localized in the fractions >1 µm,and mediated by free-living and particle-bound bacteria.