Terrestrial ecosystems are important in providing key services to humankind, but under global warming the provisioning of such ecosystem services is at risk. However, there is little consensus on how the functioning of terrestrial ecosystems will change under projected scenarios of global warming, or when we will reach or surpass thresholds and tipping points. This is largely because most studies have failed to unravel ecosystem responses to increasing temperatures in terms of the underlying non-linear responses of plants, soil organisms, and their communities. Since plants and their associated soil organisms (i.e., pathogens, mutualists, and decomposers) can vary in their responses to temperature change, global warming may disrupt or decouple interactions among coexisting and co-evolved species. This may have unforeseen consequences for key ecosystem functions, such as carbon and nutrient cycling. THRESHOLD will use a novel cross-disciplinary approach to advance our fundamental knowledge of how non-linear temperature responses transcend different levels of ecological organization. Specifically, this project aims to: 1) Establish a global network of forest-tundra and forest-alpine ecotone sites, to assess how responses of ecosystem carbon and nutrient cycling to global warming will be pushed across thresholds and tipping points. 2) Perform mesocosm experiments under different temperatures, to estimate how ecosystem process responses to global warming can be predicted from the reordering of plant and soil communities, as well as from the functional traits that they possess and express. 3) Reveal how community responses to warming and extreme temperatures can be predicted from the physiological responses of their component species. To achieve these aims, this work will utilize a powerful approach that harnesses an array of cutting-edge tools, and it will advance our conceptual understanding in an area of urgent importance for ecology and society.

Ash trees (Fraxinus spp.) in Europe are threatened by two alien invasive organisms; a deadly fungal pathogen Hymenoscyphus fraxineus that has been causing a slow, steady decline in Europe’s ash population, and emerald ash borer (EAB; Agrilus planipennis), a buprestid beetle that is quickly killing trees in eastern Europe, and moving west. There are fears that EAB will follow the same path as it did recently in USA – killing millions of ash trees, unless active research is undertaken to prevent the spread of EAB and protect the ash resource. EMERALD is a multidisciplinary and innovative project that approaches this invasion through the combination of molecular biology, analytical chemistry, sensor technology, insect ecology, and tree physiology to understand host-pest interactions and improve the options for integrated pest management in European forests. In this project, naïve and a co-evolved ash species will be investigated to understand their attractive volatile chemistry and influence on EAB’s behaviour and host preference (antixenosis), differences in host chemical defenses that either promote or deter EAB performance (antibiosis), and the confounding effect of H. fraxineus in relation to both interactions. Novel early detection tools will be developed including new lure traps and molecular assays based on optimized environmental DNA protocols of samples filtered from stem flow and canopy foliage, and portable loop mediated isothermal amplification (LAMP) to achieve point-of-use and real-time detection of EAB. The training-through-research will diversify and expand the skillset of the applicant, while also providing reciprocal teaching and new insights for the host unit. The results of this project will have tremendous value for European stakeholders and the general public for those concerned with saving the economically and ecological valuable ash in urban and rural forested environments by developing an arsenal of tools to manage the impending EAB invasion.

This proposal aims to explore the precise mechanism, overall impact and complete population of the small RNAs derived of transfer RNAs (tsRNAs) in plants. The proposed research would be carried out in a laboratory that specializes in RNA regulation and that made substantial contributions to the plant tRNA-derived sRNA field (Dr. German Martinez). Although it has been described that these molecules are highly expressed in stress conditions, we still lack a clear understanding of the biogenesis pathways that lead to tsRNA accumulation, as well as of the array of biological processes they influence and their mechanism of action. Additionally, because of the widespread presence of RNA modifications in these molecules, the unbiased genome-wide quantification is not possible with the conventional sequencing technologies. Therefore, these molecules represent a largely uncharacterized stress-responsive regulatory network in plants, and thus an exciting source of potential applications for agriculture. The experimental approach of this project will use a model plant (Arabidopsis thaliana) in order to characterize the tsRNA population and evaluate the importance of this regulatory layer under viral stress. First, a method to compare the accumulation profiles of tsRNAs based on the enzymatic removal of RNA modifications will be implemented. Second, the biogenesis pathway of tRNA-derived sRNAs will be studied using mutant plants, and how this affects viral infection will be evaluated with these mutant plants. Third, the genes targeted by tRNA-derived sRNAs will be identified using a combined approach based on the immunoprecipitation of crosslinked AGO proteins and ribosome profiling that determines the translation rate. Overall, the data that this project would obtain has the potential to shift our understanding of tsRNAs and provide cutting-edge applications for agriculture. Thus, the completion of this project would provide me a considerable professional maturity.

Phosphorus (P) is a macronutrient whose availability strongly affects many processes in terrestrial ecosystems. P is recycled through organic P (OP) decomposition, resulting in the generation of inorganic P available for plant uptake. Despite the importance of this process for P cycling and other related biogeochemical cycles, our understanding of OP decomposition is to date very poor, largely due to the lack of methods to determine the decomposition and turnover of OP in soils. In PHOSCYCLE, I will develop a novel approach to study the decomposition and turnover of OP in soils. I will lead my team to develop compound-specific isotope methods to analyze the isotope signature of carbon (C) in OP compounds, enabling us to determine for the first time the isotope signature of all important phosphomono- and diesters present in soils. We will utilize these new methods that make use of different C isotopes to quantify the decomposition rate and turnover time of OP compounds in comparison to the soil total organic C pool and non-phosphorylated organic compounds in soils on three continents under various forms of land use. In addition, we will establish how OP quality and soil minerals affect the sorption and persistence of OP in soils. Finally, we will model the turnover of the soil total OP pool as well as the cycling of P between soil and plants in a large range of ecosystems, revealing how soil OP turnover affects P cycling in these ecosystems. Besides leading to a step-change in the way we study and understand the P cycle in terrestrial ecosystems, PHOSCYCLE will also provide a new starting point for our understanding of soil organic matter dynamics and interactions between element cycles in terrestrial ecosystems.

Plant-parasitic nematodes are microscopic organisms with exceptionally broad host range that pose major challenge to global agriculture, generate a predicted loss of 12.3 percent, equivalent to $157 billion each year. The losses caused by nematodes are further enhanced when they form disease-complexes with other microbes. Endoparasitic cyst nematodes are one of two most devastating groups, infecting the roots of economically important plants. The nematodes are a persistent problem because they have evolved an ability to secrete specific proteins to exploit the host plant’s development and suppress defense responses triggered by the plant. They begin feeding only after developing a specialized feeding structure (syncytium) inside the host root, by selecting a single cell near the innermost nutrient-rich vascular tissues, causing cellular injury by passing through multiple layers of different cell files. The majority of previous research has been on syncytium formation as infection proceeds. However, it is unknown how plants respond at the cellular level to the mechanical damage caused by nematodes, which prevents the creation of resistant plants to minimize crop losses. In the proposed study, cells from two internal consecutive cell layers surrounding the vascular tissues will be studied for their molecular responses to mechanical injury. The control of lignin and suberin production, which function as physical barriers against invading pathogens, will be studied in particular. Advanced microscopic technology will be utilized to accurately produce mechanical damage in selected internal root cells using a cutting-edge method called laser ablation. It will offer a strong platform for the creation of resistance agricultural plants against plant parasitic nematodes in the long run. The project will use a variety of high-tech multidisciplinary approaches to provide a framework for researching plant physical barrier measures against invasive plant diseases.