Phylogenetic evidence for the distinction of Saaremaa and Dobrava hantaviruses

Background

Simian virus 40 (SV40) enters cells via an atypical caveolae-mediated endocytic pathway, which delivers the virus to a new intermediary compartment, the caveosome. The virus then is believed to go directly from the caveosome to the endoplasmic reticulum. Cholera toxin likewise enters via caveolae and traffics to caveosomes. But, in contrast to SV40, cholera toxin is transported from caveosomes to the endoplasmic reticulum via the Golgi. For that reason, and because the caveosome and Golgi may have some common markers, we revisited the issue of whether SV40 might access the endoplasmic reticulum via the Golgi.

Results

We confirmed our earlier finding that SV40 co localizes with the Golgi marker β-COP. However, we show that the virus does not co localize with the more discriminating Golgi markers, golgin 97 and BODIPY-ceramide.

Conclusion

The caveolae-mediated SV40 entry pathway does not intersect the Golgi. SV40 is seen to co localize with β-COP because that protein is a marker for caveosomes as well as the Golgi. Moreover, these results are consistent with the likelihood that the caveosome is a sorting organelle. In addition, there are at least two distinct but related routes by which a ligand might traffic from the caveosome to the ER; one route involving transport through the Golgi, and another pathway that does not involve the Golgi.     

Genotype × Herbivore Effect on Leaf Litter Decomposition in Betula Pendula Saplings: Ecological and Evolutionary Consequences and the Role of Secondary Metabolites

Plant genetic variation and herbivores can both influence ecosystem functioning by affecting the quantity and quality of leaf litter. Few studies have, however, investigated the effects of herbivore load on litter decomposition at plant genotype level. We reduced insect herbivory using an insecticide on one half of field-grown Betula Pendula saplings of 17 genotypes, representing random intrapopulation genetic variation, and allowed insects to naturally colonize the other half. We hypothesized that due to induced herbivore defence, saplings under natural herbivory produce litter of higher concentrations of secondary metabolites (terpenes and soluble phenolics) and have slower litter decomposition rate than saplings under reduced herbivory. We found that leaf damage was 89 and 53% lower in the insecticide treated saplings in the summer and autumn surveys, respectively, which led to 73% higher litter production. Litter decomposition rate was also affected by herbivore load, but the effect varied from positive to negative among genotypes and added up to an insignificant net effect at the population level. In contrast to our hypothesis, concentrations of terpenes and soluble phenolics were higher under reduced than natural herbivory. Those genotypes, whose leaves were most injured by herbivores, produced litter of lowest mass loss, but unlike we expected, the concentrations of terpenes and soluble phenolics were not linked to either leaf damage or litter decomposition. Our results show that (1) the genetic and herbivore effects on B. pendula litter decomposition are not mediated through variation in terpene or soluble phenolic concentrations and suggest that (2) the presumably higher insect herbivore pressure in the future warmer climate will not, at the ecological time scale, affect the mean decomposition rate in genetically diverse B. pendula populations. However, (3) due to the significant genetic variation in the response of decomposition to herbivory, evolutionary changes in mean decomposition rate are possible.     

Coping with fast climate change in northern ecosystems: mechanisms underlying the population‐level response of a specialist avian predator

Northern ecosystems are facing unprecedented climate modifications, which pose a major threat for arctic species, especially the specialist predator guild. However, the mechanisms underlying responses of predators to climate change remain poorly understood. Climate can influence fitness parameters of predators either through reduced reproduction or survival following adverse weather conditions, or via changes in the population dynamics of their main prey. Here, we combined three overlapping long‐term datasets on the breeding density and parameters of a rodent‐specialist predator, the rough‐legged buzzard Buteo lagopus, its main prey population dynamics and climate variables, collected in subarctic areas of Finland and Norway, to assess the impact of changing climate on the predator reproductive response. Rough‐legged buzzards responded to ongoing climate change by advancing their laying date (0.1 d yr^?1 over the 21 yr of the study period), as a consequence of earlier snowmelt. However, we documented for the same period a decrease in breeding success, which principally resulted from an indirect effect of changes in the dynamics of their main prey, i.e. grey‐sided voles Microtus oeconomus, and not from the expected negative effect of unfavorable weather conditions during the brood‐rearing period on nestling survival. Additionally, we showed the striking impact of autumn and winter weather conditions on vole population growth rates in subarctic ecosystems, with a strong positive correlation between mean snow depth in autumn and winter and both winter and summer population growth rates. Our results highlighted that, in northern ecosystems, ongoing climate change has the potential to impact specialist predator species through two mechanistic linkages, which may in the long‐run, threaten the viability of their populations, and lead to potential severe cascading trophic effects at the ecosystem level.     

Genetic variants of TSLP and asthma in an admixed urban population

Background

Thymic stromal lymphopoietin (TSLP), an IL7-like cytokine produced by bronchial epithelial cells is upregulated in asthma and induces dendritic cell maturation supporting a Th2 response. Environmental pollutants, including tobacco smoke and diesel exhaust particles upregulate TSLP suggesting that TSLP may be an interface between environmental pollution and immune responses in asthma. Since asthma is prevalent in urban communities, variants in the TSLP gene may be important in asthma susceptibility in these populations.

Objectives

To determine whether genetic variants in TSLP are associated with asthma in an urban admixed population.

Methodology and Main Results

Ten tag-SNPs in the TSLP gene were analyzed for association with asthma using 387 clinically diagnosed asthmatic cases and 212 healthy controls from an urban admixed population. One SNP (rs1898671) showed nominally significant association with asthma (odds ratio (OR) = 1.50; 95% confidence interval (95% CI): 1.09–2.05, p = 0.01) after adjusting for age, BMI, income, education and population stratification. Association results were consistent using two different approaches to adjust for population stratification. When stratified by smoking status, the same SNP showed a significantly increased risk associated with asthma in ex-smokers (OR = 2.00, 95% CI: 1.04–3.83, p = 0.04) but not significant in never-smokers (OR = 1.34; 95% CI: 0.93–1.94, p = 0.11). Haplotype-specific score test indicated that an elevated risk for asthma was associated with a specific haplotype of TSLP involving SNP rs1898671 (OR = 1.58, 95% CI: 1.10–2.27, p = 0.01). Association of this SNP with asthma was confirmed in an independent large population-based cohort consortium study (OR = 1.15, 95% CI: 1.07–1.23, p = 0.0003) and the results stratified by smoking status were also validated (ex-smokers: OR = 1.21, 95% CI: 1.08–1.34, p = 0.003; never-smokers: OR = 1.06, 95% CI: 0.94–1.17, p = 0.33).

Conclusions

Genetic variants in TSLP may contribute to asthma susceptibility in admixed urban populations with a gene and environment interaction.     

Induced defenses of Veronica spicata: Variability in herbivore-induced volatile organic compounds

Plants release volatile organic compounds (VOCs) that have many eco-physiological functions. Induction of plant VOCs is known to occur upon herbivory. Herbivore-induced VOCs are involved in the attraction of predators and parasitoids, a phenomenon known as an indirect defense of plants. We measured the VOC profiles of the wild species Veronica spicata with and without larval feeding and oviposition by the specialist butterfly Melitaea cinxia. V. spicata showed great plasticity when deploying indirect defences. The induction of several ubiquitous terpenoids and green leaf volatiles (GLVs) was associated with larval feeding, whereas the increase of two ketones, 6-methyl-5-hepten-2-one and t-geranylacetone and the suppression of GLVs were associated with oviposition by the butterfly.     

Effects of NR1H3 Genetic Variation on the Expression of Liver X Receptor α and the Progression of Alzheimer's Disease

Alzheimer''s disease (AD) has been postulated to involve defects in the clearance of amyloid-β (Aβ). Activation of liver X receptor α (LXRα) increases the expression of apolipoprotein E (ApoE) as well as cholesterol transporters ABCA1 and ABCG1, leading to augmented clearance of Aβ. We have previously shown that the C allele of rs7120118 in the NR1H3 gene encoding LXRα reduces the risk of AD. Here, we wanted to assess whether the rs7120118 variation affects the progression of AD and modulates the expression of NR1H3 and its downstream targets APOE, ABCA1 and ABCG1.We utilized tissue samples from the inferior temporal cortex of 87 subjects, which were subdivided according to Braak staging into mild, moderate and severe AD groups on the basis of AD-related neurofibrillary pathology. APOE ε4 allele increased soluble Aβ42 levels in the tissue samples in a dose-dependent manner, but did not affect the expression status of APOE. In contrast, the CC genotype of rs7120118 was underrepresented in the severe group, although this result did not reach statistical significance. Also, patients with the CC genotype of rs7120118 showed significantly decreased soluble Aβ42 levels as compared to the patients with TT genotype. Although the severity of AD did not affect NR1H3 expression, the mRNA levels of NR1H3 among the patients with CT genotype of rs7120118 were significantly increased as compared to the patients with TT genotype. These results suggest that genetic variation in NR1H3 modulates the expression of LXRα and the levels of soluble Aβ42.     

The impact of thermal seasonality on terrestrial endotherm food web dynamics: a revision of the Exploitation Ecosystem Hypothesis

Many terrestrial endotherm food webs constitute three trophic level cascades. Others have two trophic level dynamics (food limited herbivores; plants adapted to tackle intense herbivory) or one trophic level dynamic (herbivorous endotherms absent, thus plants compete for the few places where they can survive and grow). According to the Exploitation Ecosystems Hypothesis (EEH), these contrasting dynamics are consequences of differences in primary productivity. The productivity thresholds for changing food web dynamics were assumed to be global constants. We challenged this assumption and found that several model parameters are sensitive to the contrast between persistently warm and seasonally cold climates. In persistently warm environments, three trophic level dynamics can be expected to prevail almost everywhere, save the most extreme deserts. We revised EEH accordingly and tested it by compiling direct evidence of three and two trophic level dynamics and by studying the global distribution of felids. In seasonally cold environments, we found evidence for three trophic level dynamics only in productive ecosystems, while evidence for two trophic level dynamics appeared in ecosystems with low primary productivity. In persistently warm environments, we found evidence for three trophic level dynamics in all types of ecosystems. The distribution of felids corroborated these results. The empirical evidence thus indicates that two trophic level dynamics, as defined by EEH, are restricted to seasonally cold biomes with low primary productivity, such as the artic–alpine tundra and the temperate steppe.     

Ectomycorrhizas and water relations of trees: a review

There is plenty of evidence for improved nutrient acquisition by ectomycorrhizas in trees; however, their role in water uptake is much less clear. In addition to experiments showing improved performance during drought by mycorrhizal plants, there are several studies showing reduced root hydraulic conductivity and reduced water uptake in mycorrhizal roots. The clearest direct mechanism for increased water uptake is the increased extension growth and absorbing surface area, particularly in fungal species with external mycelium of the long-distance exploration type. Some studies have found increased aquaporin function and, consequently, increased root hydraulic conductivity in ectomycorrhizal plants while other studies showed no effect of ectomycorrhizal associations on root water flow properties. The aquaporin function of the fungal hyphae is also likely to be important for the uptake of water by the ectomycorrhizal plant, but more work needs to be done in this area. The best-known indirect mechanism for mycorrhizal effects on water relations is improved nutrient status of the host. Others include altered carbohydrate assimilation via stomatal function, possibly mediated by changes in growth regulator balance; increased sink strength in mycorrhizal roots; antioxidant metabolism; and changes in osmotic adjustment. None of these possibilities has been sufficiently explored. The mycorrhizal structure may also reduce water movement because of different fine root architecture (thickness), cell wall hydrophobicity or the larger number of membranes that water has to cross on the way from the soil to the xylem. In future studies, pot experiments comparing mycorrhizal and nonmycorrhizal plants will still be useful in studying well-defined physiological details. However, the quantitative importance of ectomycorrhizas for tree water uptake and water relations can only be assessed by field studies using innovative approaches. Hydraulic redistribution can support nutrient uptake during prolonged dry periods. In large trees with deep root systems, it may turn out that the most important function of mycorrhizas during drought is to facilitate nutrient acquisition.     

Cold acclimation was partially impaired in boron deficient Norway spruce seedlings

Susceptibility of trees to freezing injury has been suggested to increase in boron (B) deficiency but there is no experimental evidence to support this proposition. In this study, Norway spruce (Picea abies L. Karst.) seedlings were cultivated for two growing seasons in deficient, intermediate and ‘optimal’ B levels. Cold hardening of the seedlings was measured after the second growing season. Freezing tolerance in tips of shoots, needles, stems and roots was determined by controlled freezing tests and electrolyte leakage method, and that of buds, in addition, by differential thermal analysis (DTA). Electrical impedance was used to monitor changes in the apoplastic space during cold acclimation. Root dry weight and shoot height growth were lower in B deficiency. Cold acclimation of buds and stems was reduced by B deficiency. When hardened seedlings were subjected to subzero temperatures for 3 weeks, extracellular electrical resistance of stems became the highest at the lowest B supply which was probably due to decreased desiccation tolerance. As a conclusion, susceptibility to freezing damage may be increased by B deficiency in Norway spruce trees.     

Phenolic compounds in Norway spruce as affected by boron nutrition at the end of the growing season

The increase in concentrations of phenolic compounds in boron (B) deficiency has been demonstrated in many herbaceous plant species, but information on woody plants is scarce. It has been suggested that accumulation of phenolic compounds plays a role in the development of cold hardiness in herbaceous plants but also that B deficiency decreases winter hardiness. Here we study the effects of B nutrition on phenolic compounds in Norway spruce (Picea abies L.) in the course of cold acclimation. Phenolic compounds were analysed in Norway spruce seedlings from three different B-fertilisation treatments in two harvests: non-acclimated and cold-acclimated seedlings. Norway spruce phenolic compounds consisted mainly of condensed tannins. During B deficiency, condensed tannins and monocoumaroyl–astragalin der. 1 increased in non-acclimated seedlings. The increase in tannins was 21%, which was nearly significant. However, the effect of B on phenolic compounds was almost absent in cold-acclimated seedlings. The condensed tannin concentration increased much more with time in the simulated autumn than due to B deficiency, and we conclude that the B effect was probably not large enough to be important for the hardening of the seedlings. The total phenolic concentrations more than doubled during the course of cold hardening suggesting that phenolics have a role in the winter hardiness in Norway spruce.