Understanding how the natural environment influences DMSP production by plants

Dimethylsulfoniopropionate (DMSP) is an abundant and important compound in biology and the environment, where it has key roles in nutrient cycling, stress tolerance and as the major precursor to the climate-active gas dimethyl sulfide (DMS). Some plants produce DMSP, e.g. Spartina, which is likely the major DMSP producer in saltmarsh environments - global hotspots for DMSP/DMS production. Indeed, DMSP production is thought to allow plants to tolerate conditions associated with growing at the coast. Currently, few plants are known to make DMSP and the precise role of DMSP is unknown - a consequence of no plant DMSP synthesis genes having hitherto been described. Building on our identification and ratification of plant DMSP synthesis genes, the student will study how and why plants produce DMSP. Our work will have important consequences for better evaluating plant contributions to global DMS and DMSP production in the natural environment.

Objectives:
1. Evaluate plant production of DMSP/DMS in the natural environment
It is currently unclear when and where plants produce DMSP/DMS. The student will therefore assess DMSP levels in Spartina anglica sampled from Norfolk saltmarshes, measuring DMSP in different tissues (roots, leaves, stems, inflorescence) over an annual season using established GC and LCMS techniques. The student will also compare different sites to assess production and DMSP/DMS flux in plants from high- and low-marsh environments.

2. Assess DMSP production in plants grown under controlled environments
To test our hypothesis that plants produce DMSP to tolerate environmental stress, the student will grow model species under controlled lab conditions in the presence/absence of different stresses and assess plant growth (e.g. fresh/dry weight, root length) and measure DMSP levels using GC. The student will initially focus on salt and osmotic stress, as we believe these are the most important stresses governing DMSP production in S. anglica. The effects of nitrogen and sulfur will also be explored, as these are important for regulating microbial DMSP production and thus likely important in plants too.

3. Determine environmental factors that govern DMSP production
We have identified candidate DMSP synthesis genes in S. anglica and the student will measure expression of these in the samples collected in Objective 1 using qRT-PCR. Gene expression will also be measured in samples from Objective 2 to determine how abiotic stress regulates DMSP production. Enzyme function will additionally be studied using established in vitro assays to measure DMSP synthesis rates.

4. Establish how widespread DMSP production is in plants
The student will perform bioinformatics analyses using existing genomic/transcriptomic datasets to assess distribution of DMSP synthesis genes. Based on these predictions, diverse plants will be sampled from their natural environments and assessed for DMSP production. This work will include other saltmarsh plants, model species and crops, and will determine the scale and diversity of plant DMSP production.

The student will be involved in all aspects of the project including experimental design, data collection, analysis and management. This project will give them excellent opportunities for independence and to receive a broad training in diverse aspects of cutting-edge research on environmental processes.