Synthesis and transport of DMSP and glycine betaine in model diatoms

Bermejo Martinez, Ana (2019) Synthesis and transport of DMSP and glycine betaine in model diatoms. Doctoral thesis, University of East Anglia.

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Dimethylsulfoniopropionate (DMSP) and glycine betaine (GBT) are very abundant sulfurous and nitrogenous compatible solutes, respectively. Their catabolites play a key role in the environment being climate active compounds, dimethylsulfide (DMS) and trimethylamine (TMA) or methane. DMSP has many suggested roles in the cell including cryoprotection, oxidative stress relief, osmoprotection amongst others in the marine environments. GBT has been proven to be an effective osmolyte in all kingdoms of life. The methylthiohydroxybutyrate (MTHB) methyltransferase enzyme catalysing the key step in DMSP biosynthesis has recently been identified in bacteria (DsyB) and many phytoplankton (DSYB). However, the majority of diatoms with sequenced genomes lack this DSYB, despite using the same pathway for DMSP biosynthesis. Likewise, very little is known about how diatoms and phytoplankton synthesise GBT despite the biosynthetic pathways being well understood. Nor it is known the mechanism diatoms use to transport these molecules. A novel methyltransferase involved in DMSP synthesis was found in the model diatoms T. pseudonana and P. tricornutum named DSYD (DMSHB synthase in diatoms). DSYD was present in other diatoms, brown and green algae and a gamma-proteobacterium. This is the first gene identified for DMSP synthesis in alga. Furthermore, a functional methyltransferase able to methylate glycine to glycine betaine named GSDMT (glycine sarcosine dimethylglycine methyltransferase) was found in these two diatoms and many bacteria, highlighting the prevalence of this pathway previously thought to be less common than the choline pathway. In addition, a novel enzyme present in bacteria was able of synthesising both DMSP and GBT. These results stress the close relationship between these two abundant osmolytes and show that the contribution of bacterial DMSP production has been underestimated.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Chris White
Date Deposited: 14 Apr 2021 08:13
Last Modified: 30 Sep 2022 01:38


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