Function and metabolism of Dimethylsulfoniopropionate by higher plants and associated Rhizosphere bacteria

Allen, Mellieha Grace Evangeline (2023) Function and metabolism of Dimethylsulfoniopropionate by higher plants and associated Rhizosphere bacteria. Doctoral thesis, University of East Anglia.

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Dimethylsulfoniopropionate (DMSP) is one of the Earth’s most abundant organosulfur compounds, with more than 8 billion tonnes produced annually by marine microorganisms and some plants as an antistress compound. Comparatively few higher plants were known to be high producers, including Sugarcane, Sea Daisies and Cordgrasses. Thro ugh sampling a large variety of wild plants, we found that all plants produce DMSP, albeit at low levels, including the model organism Arabidopsis thaliana. Additionally, DMSP production is increased in response to salt stress, suggesting it functions as an osmolyte in higher plants. DMSP is known to be produced through the methylation pathway, confirmed when MMT- homozygous knockout A. thaliana produced significantly less DMSP compared to their wildtype counterparts, and were significantly more stressed in response to salt. Furthermore, when released into the environment, this DMSP is a major carbon and sulfur source for marine microbes through catabolism that yields the climate-active gases and signalling molecules dimethylsulfide (DMS) via DMSP lyase enzymes and methanethiol (MeSH) via DMSP demethylation. Spartina anglica, an invasive cordgrass, is one of Earth’s highest accumulators of DMSP and is responsible for the far higher DMSP levels per unit area in saltmarsh environments compared to surface seawaters. Spartina, which does not cleave DMSP itself, is proposed to feed this nutrient to its holobiome in return for vitamins, hormones and/or antibiotic activities. Here we conducted stable-isotope probing experiments with 13C-DMSP to study DMSP-mediated interactions between Spartina and its holobiome. This work identified the abundant and important group of marine bacteria, the Roseobacters, as major degraders of DMSP in the Spartina rhizosphere via their DMSP demethylation DmdA and DMSP lyase DddL enzymes. Cultivation-dependent work supported Roseobacters, well known to catabolise DMSP and interact with algae, as key bacteria assimilating DMSP in the Spartina rhizosphere, potentially interacting with the plant, and liberating significant amounts of DMS and MeSH.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Nicola Veasy
Date Deposited: 26 Jun 2024 09:54
Last Modified: 26 Jun 2024 09:54


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