description
- The quaternary nitrogen compound betaine is the most abundant osmolyte on Earth. Betaine production in organisms protects against osmotic, temperature and drought stresses and its release into the environment provides dissolved organic nitrogen. Also, it is desirable for crops to have high betaine levels due to its wide-ranging health benefits. Betaine synthesis is well understood in many organisms but there are no detailed studies on betaine synthesis in any marine eukaryotic phytoplankton - not a single synthesis gene is reported. Using diatoms as model phytoplankton we have identified a betaine synthase gene that when cloned in Escherichia coli confers enhanced salt tolerance and the ability to produce betaine from glycine. With the need to maximize nutritional value and crop production in the modern world, science has successfully explored transgenic introduction of betaine synthesis genes into crop plants to enhance their stress tolerance and betaine production. Given that the diatom synthase has no significant identity to any characterised betaine synthesis enzyme, it is a good candidate for transgenic stress tolerance studies in higher plants. This PhD aims to demonstrate the role of this betaine synthase in Thalassiosira pseudonana via overexpression and knocking down of the corresponding gene in this model diatom. We will study gene regulation and the physiology of transgenic diatoms under varied environmental conditions and monitor their osmolyte production by liquid chromatography/mass spectroscopy. To explore the potential of producing stress tolerant higher plants, the diatom betaine synthase will be introduced and expressed in Arabidopsis and wheat. Comprehensive training will be provided at UEA by Mock and Todd, and at JIC by Balk and Uauy.