Abstract
Dimethylsulphide (DMS) is a semivolatile organic sulphur compound that accounts for 50-60% of the total natural reduced sulphur flux to the atmosphere. In the atmosphere, DMS is oxidised to acidic sulphur aerosols which can act as condensation nuclei for water vapour, leading to formation of clouds over the ocean. DMS is produced mostly through biogenic processes, mainly through enzymatic cleavage of dimethylsulfoniopropionate (DMSP), a compound that is produced in several groups of marine phytoplankton. DMSP appears to act both as an osmolyte and a cryoprotectant as well as an antioxidant. However, the molecular mechanisms behind biosynthesis, processing, sensing and uptake of DMSP in phytoplankton are unknown. Here, we propose to use functional genomics tools in combination with biochemical and molecular biology analyses to identify the molecular components and pathways involved in the cycling of DMSP and DMS in the oceans. We utilise the available genome sequences of three ecologically important phytoplankton species: the diatom T. pseudonana, the haptophyte E. huxleyi and the prasinophyte M. pusilla. Whole-genome microarrays will be designed for each species. Microarray experiments will be performed based on unique properties for each species with regard to different aspects of DMSP synthesis, processing and sensing. These experiments will be combined with chromatographic measurements of DMS and DMSP and other physiological data. The resulting datasets will be mined for candidate genes. Selected genes will be subjected to functional analyses using molecular methods. Purified recombinant protein will be used for biochemical analyses. Results from this project will provide novel knowledge on key processes in the cycling of DMSP and DMS in three important classes of phytoplankton. Implementation of this knowledge into suitable models will improve prediction of DMS production and its effect on the global sulphur cycle and cloud formation in future scenarios.
Norway