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

二甲基磺酸丙酯(DMSP)是一种抗应激化合物，在全球营养和硫循环、信号传递和气候变化中起着关键作用。DMSP具有渗透保护剂、低温保护剂、氧化应激保护剂和放牧威慑作用。盐沼是全球DMSP生产的热点，因为那里生长的大米草产生高浓度的DMSP。尽管已经知道了这些植物中DMSP合成的生化途径，但关键的酶的特性仍然没有被发现。本博士学位论文旨在鉴定大米草DMSP合成的两个关键酶。这些酶被称为S甲硫氨酸脱羧酶(SDC)和DMSP胺氧化酶(DOX)，是普通植物中唯一缺失的酶。博士项目将研究如何使用分子和生化技术(例如，RNA-seq)来识别候选的SDC和DOX基因。该项目将通过克隆和酶学来鉴定功能基因，并研究它们在宿主植物中对环境条件的反应。将进行培训，以便将这些基因转移到例如拟南芥中，从而有可能产生DMSP。利用分析化学，该项目将表征转基因品系产生DMSP的能力，并将研究品系的生长和生理，以确定环境因素，如温度、盐度、氧化应激和干旱，是否影响它们的生产力和生长。在现代世界，在目前不适合农业的次优盐碱/干旱环境中种植作物的能力非常重要。

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.