Adaptations and responses of the common dandelion to low atmospheric pressure in high‐altitude environments

Atmospheric pressure is an important, yet understudied factor that may shape plant ecology and evolution. By growing plants under controlled conditions at different experimental stations in the Swiss alps, we evaluated the impact of ecologically realistic atmospheric pressures between 660 and 950 hPa on the growth and defence of different dandelion populations. Low atmospheric pressure was associated with reduced root growth and defensive sesquiterpene lactone production. Defence suppression only occurred in populations originating from lower altitudes. Populations from higher altitudes constitutively produced less sesquiterpene lactones and did not suffer from suppression under low atmospheric pressure. Synthesis. We conclude that atmospheric pressure modulates root growth and defence traits, and that evolutionary history shapes plant phenotypic responses to atmospheric pressure. Our findings have important implications for our understanding of altitudinal gradients and the future use of plants as a source of food and bioactive metabolites in extraterrestrial habitats

Impact of Seasonal and Temperature-Dependent Variation in Root Defense Metabolites on Herbivore Preference in Taraxacum officinale

Plants experience seasonal fluctuations in abiotic and biotic factors such as herbivore attack rates. If and how root defense expression co-varies with seasonal fluctuations in abiotic factors and root herbivore attack rates is not well understood. Here, we evaluated seasonal changes in defensive root latex chemistry of Taraxacum officinale plants in the field and correlated the changes with seasonal fluctuations in abiotic factors and damage potential by Melolontha melolontha, a major natural enemy of T. officinale. We then explored the causality and consequences of these relationships under controlled conditions. The concentration of the defensive sesquiterpene lactone taraxinic acid β-D glucopyranosyl ester (TA-G) varied substantially over the year and was most strongly correlated to mean monthly temperature. Both temperature and TA-G levels were correlated with annual fluctuations in potential M. melolontha damage. Under controlled conditions, plants grown under high temperature produced more TA-G and were less attractive for M. melolontha. However, temperature-dependent M. melolontha feeding preferences were not significantly altered in TA-G deficient transgenic lines. Our results suggest that fluctuations in temperature leads to variation in the production of a root defensive metabolites that co-varies with expected attack of a major root herbivore. Temperature-dependent herbivore preference, however, is likely to be modulated by other phenotypic alterations

Adapted dandelions increase seed dispersal potential when they are attacked by root herbivores

Plants allow their offspring to escape unfavourable local conditions through seed dispersal. Whether plants use this strategy to escape herbivores is not well understood. Here, we explore how different Taraxacum officinale populations modify seed dispersal in response to root herbivore attack by Melolontha melolontha in the field. Root herbivore attack increases seed dispersal potential through a reduction in seed weight in populations that have evolved under high root herbivore pressure, but not in populations that have evolved under low pressure. This increase in dispersal potential is associated with reduced germination, suggesting that adapted plants trade dispersal for establishment. Analysis of vegetative growth parameters suggests that increased dispersal is not the result of stress flowering. These results suggest that root herbivory selects for genotypes that increase their dispersal ability in response to herbivore attack

A herbivore tag-and-trace system reveals contact- and density-dependent repellence of a root toxin

Foraging behavior of root feeding organisms strongly affects plant-environment-interactions and ecosystem processes. However, the impact of plant chemistry on root herbivore movement in the soil is poorly understood. Here, we apply a simple technique to trace the movement of soil-dwelling insects in their habitats without disturbing or restricting their interactions with host plants. We tagged the root feeding larvae of Melolontha melolontha with a copper ring and repeatedly located their position in relation to their preferred host plant, Taraxacum officinale, using a commercial metal detector. This method was validated and used to study the influence of the sesquiterpene lactone taraxinic acid β-D-glucopyranosyl ester (TA-G) on the foraging of M. melolontha. TA-G is stored in the latex of T. officinale and protects the roots from herbivory. Using behavioral arenas with TA-G deficient and control plants, we tested the impact of physical root access and plant distance on the effect of TA-G on M. melolontha. The larvae preferred TA-G deficient plants to control plants, but only when physical root contact was possible and the plants were separated by 5 cm. Melolontha melolontha showed no preference for TA-G deficient plants when the plants were grown 15 cm apart, which may indicate a trade-off between the cost of movement and the benefit of consuming less toxic food. We demonstrate that M. melolontha integrates host plant quality and distance into its foraging patterns and suggest that plant chemistry affects root herbivore behavior in a plant-density dependent manner. © 2017, Springer Science+Business Media New York

Genomic investigations of unexplained acute hepatitis in children

Since its first identification in Scotland, over 1,000 cases of unexplained paediatric hepatitis in children have been reported worldwide, including 278 cases in the UK1. Here we report an investigation of 38 cases, 66 age-matched immunocompetent controls and 21 immunocompromised comparator participants, using a combination of genomic, transcriptomic, proteomic and immunohistochemical methods. We detected high levels of adeno-associated virus 2 (AAV2) DNA in the liver, blood, plasma or stool from 27 of 28 cases. We found low levels of adenovirus (HAdV) and human herpesvirus 6B (HHV-6B) in 23 of 31 and 16 of 23, respectively, of the cases tested. By contrast, AAV2 was infrequently detected and at low titre in the blood or the liver from control children with HAdV, even when profoundly immunosuppressed. AAV2, HAdV and HHV-6 phylogeny excluded the emergence of novel strains in cases. Histological analyses of explanted livers showed enrichment for T cells and B lineage cells. Proteomic comparison of liver tissue from cases and healthy controls identified increased expression of HLA class 2, immunoglobulin variable regions and complement proteins. HAdV and AAV2 proteins were not detected in the livers. Instead, we identified AAV2 DNA complexes reflecting both HAdV-mediated and HHV-6B-mediated replication. We hypothesize that high levels of abnormal AAV2 replication products aided by HAdV and, in severe cases, HHV-6B may have triggered immune-mediated hepatic disease in genetically and immunologically predisposed children

Heritable variation in root secondary metabolites is associated with recent climate

Plants can adapt to changing environments by adjusting the production and maintenance of diverse sets of bioactive secondary metabolites. To date, the impact of climatic conditions relative to other factors such as soil abiotic factors and herbivore pressure on the evolution of plant secondary metabolites is poorly understood, especially for plant roots. We explored associations between root latex secondary metabolites in 63 Taraxacum officinale populations across Switzerland and climatic conditions, soil abiotic parameters, root herbivore pressure and cytotype distribution. To assess the contribution of environmental effects, root secondary metabolites were measured in F0 plants in nature and F2 plants under controlled greenhouse conditions. Concentrations of root latex secondary metabolites were most strongly associated with climatic conditions, while current soil abiotic factors or root herbivore pressure did not show a clear association with root latex chemistry. Results were similar for natural and controlled conditions, suggesting heritable variation rather than environmental plasticity as underlying factor. Synthesis . We conclude that climatic conditions likely play a major role in the evolution of root secondary metabolites. These results may hint at a novel role of root latex metabolites in tolerance of abiotic stress

Transcriptional Landscapes of Divergent Sporophyte Development in Two Mosses, Physcomitrium (Physcomitrella) patens and Funaria hygrometrica

Understanding the molecular basis of morphological shifts is a fundamental question of evolutionary biology. New morphologies may arise through the birth/death of genes (gene gain/loss) or by reutilizing existing gene sets. Yet, the relative contribution of these two processes to radical morphological shifts is still poorly understood. Here, we use the model system of two mosses, Funaria hygrometrica and Physcomitrium (Physcomitrella) patens, to investigate the molecular mechanisms underlying contrasting sporophyte architectures. We used comparative analysis of time-series expression data for four stages of sporophyte development in both species to address this question in detail. We found that large-scale differences in sporophytic architecture are mainly governed by orthologous (i.e., shared) genes frequently experiencing temporal gene expression shifts between the two species. While the absolute number of species-specific genes expressed during sporophyte development is somewhat smaller, we observed a significant increase of their proportion in preferentially sporophyte expressed genes, suggesting a fundamental role in the sporophyte phase. However, further functional studies are necessary to determine their contribution to diverging sporophyte morphologies. Our results add to the growing set of studies suggesting that radical changes in morphology may rely on the heterochronic expression of conserved regulators

MS-DATA

The data set includes insect performance, plant growth and plant physiology

Decay detection in Norway spruce (Picea abies) with the Rotfinder instrument

Wood decay limits the function of Norway spruce (Picea abies (L.) H.Karst.) for wood production and in protection forests (i.e. forests protecting against natural hazards). Therefore, more detailed knowledge about the presence and extent of decay in living trees is highly relevant for both the timber industry and risk management strategies. However, decay detection in living Norway spruce trees is not sufficiently possible by visual methods. One possibility to overcome this problem are indirect, non- or least-destructive measurement devices such as the decay detector Rotfinder. Yet, the influence of climatic variables on the reliability of decay detection determined with the Rotfinder is not sufficiently known. Therefore, we assessed the influences of several climatic variables on the Rotfinder values continuously over one year at the same measuring position. Additionally, we determined a threshold value for decay detection in single Norway spruce trees in Central Europe. Regardless of the temperature, Rotfinder values measured over one year were mainly influenced by internal decay status, i.e. damage degree, which explained about 85% of the variation based on a generalized linear mixed effects model in this temperature range (about 6–27 °C). Together with fluctuations in air temperature, about 87% of the variation in Rotfinder values could be accounted for. For decay detection in single Norway spruce trees, a maximum threshold value of about 11,000 Rotfinder units (RU) was identified, equivalent to about 36% of the Rotfinder values measured for intact trees. Our results indicate that the Rotfinder can be used successfully for decay detection in single Norway spruce trees under Central European conditions

Data from: Neighborhood effects determine plant-herbivore interactions below ground

1. Plant neighbors can strongly influence the interactions between herbivores and focal plants, for instance by providing food of different quality (consumptive effects) or by changing the behavior and metabolism of the herbivore and the focal plant without being consumed (non-consumptive effects). Determining the species-specific contributions of consumptive and non-consumptive effects is important to understand the ecophysiological mechanisms which underlie neighborhood effects. 2. We quantified the impact of nine different grassland plant species on the interaction between Taraxacum officinale and the root-feeding insect Melolontha melolontha. We investigated the contribution of consumptive and non-consumptive effects to the observed patterns, and evaluated the impact of neighboring plants on the growth and physiology of T. officinale upon M. melolontha attack. 3. Melolontha melolontha growth was strongly affected by the presence of different neighboring species. The three grass species increased larval growth when growing with T. officinale, with Poa pratensis having a synergistic effect in the mixture compared to both monocultures. The forb Centaurea stoebe reduced larval growth when growing with T. officinale or alone. The other five species had no measurable impact on larval performance. Based on these results, P. pratensis and C. stoebe were selected for further experiments. 4. Diet-mixing experiments showed that P. pratensis increased M. melolontha growth when offered together with T. officinale, while C. stoebe suppressed it. When feeding was restricted to artificial diet, larval growth was not changed by the presence of P. pratensis or C. stoebe. However, when feeding was restricted to T. officinale, larval growth was increased by both heterospecific neighbors. Biomass and primary metabolism of T. officinale under attack by M. melolontha was also altered by the presence of C. stoebe and P. pratensis. Together, these results show that consumptive and non-consumptive effects can explain the positive effect of P. pratensis. By contrast, the negative effect of C. stoebe is likely driven exclusively by intoxication. 5. Synthesis. The performed experiments suggest that different combinations of consumptive and non-consumptive effects are likely to contribute to the diversity of neighborhood effects in nature. Furthermore, they show that neighborhood effects are important factors in below ground plant-insect interactions