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How plants influence their root microbiome during phosphate starvation

Primary Supervisor: Dr Alex Jones, School of Life Sciences

Secondary supervisor: Professor Gary Bending

PhD project title: How plants influence their root microbiome during phosphate starvation.

University of Registration: University of Warwick

Project outline:

Our food supply relies on plants, either directly through consumption of leaves, seeds and roots or as feedstock for animals. Food shortages may seem unimaginable to Europeans but the effects of drought, climate change and poor soils all contribute to the devastating effects of poverty. If you are unmoved by the plight of others, Europe might not be immune to global changes; for example, the UK imports roughly 60% of its food. One contributing factor to soil quality is the availability of the essential micronutrient phosphorus (P) which often limits plant growth, reduces crop yields and requires the application of fertilizer. Approximately, 15 million tonnes of phosphorus are mined annually to meet global needs for fertilizer, but this resource is limited and could be exhausted in as little as 30 years. Substantial amounts of phosphate are lost through inefficiencies in application, leaching from the soil and poor uptake by plants. Lost P fertilizer can cause environmental damage to freshwater systems through eutrophication. Therefore, if we can improve how plants take up P from the soil, we can contribute in a meaningful way to improving food security. The objective of this project is to understand, at the molecular level of proteins, how plants adapt root growth in response to low P conditions.

Plant root growth might seem simple, but roots adapt rapidly to changing environmental conditions such as the availability of water, nutrients, microbes and adverse conditions such as low phosphate (P). The roots of the model plant Arabidopsis thaliana display rapid and dramatic changes in response to low P; they become very hairy. Root hairs are simple tubular protrusions from epidermal cells, they grow quickly and provide an excellent method to very rapidly increase the surface area of a root. This increase in surface area is matched with a surge of transporters to the plasma membrane, and secretion of plants phosphatases to increase mobilisation and uptake of P. However, plants rely heavily on the activity of microbes to mobilise phosphate (as only the inorganic form of P can be taken up) so the plant also secretes sugars and carboxylic acids to enhance the microbiome in the rhizosphere.

Current research in the Jones group has focused on two varieties of the crop plant Brassica olereacea, that show dramatically different responses to phosphate starvation. We have identified novel secreted phosphatases and developed assays to quantify secreted organic compounds (sugars, and carboxylic acids) along with plant hormones. But we have not yet examined the interaction of these root adaptations with microbes.

This PhD project would seek to build upon our current research and established methods to further explore the interaction between plant roots and microbes during phosphate starvation. You would expand our existing research by exploring the functional interaction of plant roots with specific beneficial bacteria (such as Pseudomonas putida BIRD-1) that are well-known to promote plant growth. You would also characterise our novel phosphatase and, as P. puiditasecretes its own phosphatases, ask if the plant and bacterial enzymes have complimentary functions. There is scope for moving away from Brassica olereacea to other crop plants, such as rice or maize, and possibly collaboration with researchers in Kenya looking at forage grasses. This project will provide you with a wide range of skills from plant physiology, biochemistry to quantitative mass spectrometry.

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

Techniques that will be undertaken during the project:

  • Plant and microbe cultivation in hydroponic systems
  • protein and metabolite extraction from plant roots
  • Cloning and expression of modified proteins in plants and bacteria
  • Protein biochemistry; purification of protein complexes
  • Protein interaction analysis
  • Quantitative proteomics and metabolite analysis using mass spectrometry
  • Image and data analysis of protein and hormone reporters
  • Modeling of proteins and hormone dynamics across roots

Contact: Dr Alex Jones, University of Warwick