How do plants make Earth's most abundant organosulfur molecule?

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Dimethylsulfoniopropionate (DMSP) is an antistress compound with key roles in global nutrient and sulfur cycling, signaling and climate. DMSP functions as an osmoprotectant, cryoprotectant, protectant against oxidative stress and a grazing deterrent. Saltmarshes are global hotspots for DMSP production because Spartina grass growing there produce high intracellular concentrations of DMSP. Despite knowing the biochemical pathway for DMSP synthesis in these plants the key enzyme identities remain undiscovered. This PhD aims to identify the two key Spartina DMSP synthesis enzymes. These enzymes, known as S-methyl-methionine decarboxylase (SDC) and DMSP-amine oxidase (DOX), are the only enzymes missing from common plants. The PhD project will investigate how to use molecular and biochemical techniques (e.g., RNA-seq) to identify candidate SDC and DOX genes. The project will identify functional genes through cloning and enzymology and study their expression in the host plant in response to environmental conditions. Training will be given to transfer these genes into e.g. Arabidopsis, and thus the potential to make DMSP. Using analytical chemistry, the project will characterise the ability of the transgenic lines to produce DMSP and will study the growth and the physiology of the lines to determine if environmental factors, e.g., temperature, salinity, oxidative stress and drought, affect their productivity and growth. In the modern world, the ability to produce crops in sub-optimal saline/drought ridden environments, not currently suitable for agriculture, is of high importance.