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Impact of increasing environmental CO2 on plant immunity

Primary Supervisor: Dr Estrella Luna-Diez, School of Biosciences

Secondary supervisor: Dr Graeme Kettles

PhD project title: Impact of increasing environmental CO2 on plant immunity

University of Registration: University of Birmingham

Project outline:

Global climate change, including anthropogenic activity, has raised atmospheric carbon dioxide (CO2) level significantly (~40%) from the pre-industrial era. This is predicted to rise further over the course of the 21st century, and will have significant impact on productivity of the world’s most important food crops. Whilst it has been speculated that this may increase crop productivity due to a “carbon fertiliser” effect, the impact this will have on the interactions between crop plants and their pathogens and pests is unknown1.

The world’s growing population challenges humanity to increase food production by 70% in the next 40 years. However, pathogens can claim up to 40% of crop yields. Filamentous pathogens (e.g. fungi and oomycetes) are exceptionally problematic to control as their evolutionary capacity makes them highly proficient at overcoming the resistance offered by genes or chemical pesticides. Current methods of control depend largely on the use of pesticides, but their use is under strict regulation due to their toxicity. Therefore, it is urgent to develop alternative strategies to control diseases.

Recently, several studies have reported on the detailed mechanisms by which elevated CO2 (eCO2) can impact plant resistance to disease2. For example, changes in CO2 concentration alter the capacity of some plants to express priming of defence, a phenomenon that can generally be understood as a plant vaccine and results on a faster and stronger defence response against pathogens3. However, these studies have largely focussed on the model plant Arabidopsis thaliana. In crop and tree species, only a handful of primarily descriptive studies have explored such interactions, and mechanistic insights are missing. Importantly, the effect of eCO2 on pathogen behaviour and virulence has not been reported.

The primary objective of this PhD project is to gain a mechanistic understanding of how plant immunity and pathogen infection strategies will be modified in a future eCO2 world.

Using knowledge gained from A. thaliana as a springboard, this project will explore the impact of eCO2 on disease resistance in two economically-relevant crops, wheat and tomato, and different tree species in a mature forest (including oak trees), against filamentous pathogens. Both crop species have fully sequenced genomes, significant genetic resources and available germplasm plus tractable model pathosystems which will facilitate a wide range of experimental approaches. Translational experiments in trees will offer opportunities for method development.

It is expected that the project will focus on the following key areas;

  • Pathogen bioassays to assess any change in resistance or susceptibility of both plants to a panel of necrotrophic and (hemi)biotrophic filamentous pathogens.
  • Virulence assays in order to assess the impact of eCO2 in pathogen infection strategies.
  • Investigation into the expression of priming at different mechanistic levels: gene expression, plant hormone levels and other signalling components.
  • Impact of eCO2 on the robustness of the PAMP-triggered immunity (PTI) and effector-triggered immunity (ETI) branches of the plant immune system.
  • Role of plant physical barriers and surface structures such as stomata and trichomes on relative susceptibility to pathogens under eCO2
  • In situ analysis of impacts of CO2 in a natural mature woodland on tree immunity through experiments performed at the Free Air CO2 Enrichment (FACE) facilities in Staffordshire.

This exciting project will use breakthrough methodology in reproducing future climate conditions to provide the perfect comparative platform for identification of the effect of rising CO2 concentration in the capacity of pathogens to infect, and plants to defend themselves. This work will provide a revolutionary steps-ahead strategy in the fight against biological threats that will contribute towards food security.

BBSRC Strategic Research Priority: Sustainable Agriculture and Food: Plant and Crop Science & Understanding the Rules of Life: Immunology & Microbiology & Plant Science

    Techniques that will be undertaken during the project:

    The strength of the team is based on the multidisciplinary research assets of the members, as they are highly skilled in fungal and plant genetics, phytopathology, molecular biology, cell biology, biochemistry and high-throughput patho-assays.

    During the project, the student will learn the following techniques:

    • Plant growth and cultivation of different plant species, including models, crops and trees.
    • Microbiological handling and manipulation of key pathogens with high environmental importance, including pathogen bioassays.
    • Work with breakthrough methodology in reproducibility of future CO2 This will be achieved in different settings, including growth cabinets, greenhouse cubicles and in a mature forest at the FACE experiment in in the Birmingham Institute of Forest Research (BIFoR) located in Staffordshire.
    • Forest experimental development, management and sampling at BIFoR-FACE
    • Different microscopy techniques, including confocal microscopy
    • Transcriptomic (RNA-seq) analysis
    • Metabolomics and plant hormone profiling
    • Computational techniques for the analysis and integration of omics data

    Contact: Dr Estrella Luna-Diez, University of Birmingham