Earth's coolest organosulfur molecule: understanding how agriculture can be more cooling to the climate

每年有数十亿吨的有机硫化合物二甲基磺基丙酸酯(DMSP)由海洋藻类、珊瑚和细菌产生，但植物也会制造这种重要的分子，包括玉米和西红柿等作物。DMSP是全球硫循环的关键，因为它是气候活性气体二甲基硫化物(DMS)的主要前体。在海洋环境中，DMS给海边带来了独特的气味，许多动物和鸟类将其用作与藻类食物相关的化学诱导剂。二甲基硫在大气中被氧化成硫酸盐，从而加速云的形成。这些云层影响到达地球表面的太阳光的数量，进而通过引起局部降温效应来影响气候。硫磺以雨水的形式返回陆地，完成循环。DMSP和DMS的生产传统上与海洋环境和海岸有关。例如，盐沼是DMSP/DMS合成的热点，占全球DMS排放量的10%。然而，新的数据(包括我们自己的数据)表明，农业系统中也存在大量的DMSP/DMS产量。我们最近发现了许多产生DMSP的不同作物。DMSP的生产可能会保护这些作物免受环境压力，如盐分和营养限制，但这一点尚未确定。我们还发现，作物根际含有比海水中通常发现的更多的DMSP，并排放DMS。此外，我们还分离出了能将DMSP转化为DMS并促进植物生长的作物相关细菌。在这个项目中，我们将评估DMSP/DMS生产在农业中的重要性，并评估利用或操纵这些过程是否可以提高农业生产力，提高作物产量和气候降温DMS产量。我们将研究不同作物在一个季节生长在田间的不同作物对DMSP和DMS的农业产量和周转率。通过构建和部署远程DMS田间传感器，我们将实时跟踪农作物DMS的生产，为我们提供关于DMS从农业释放到大气中的高分辨率数据，以便为模型提供信息。我们还将评估与作物相互作用的微生物的丰度、多样性和潜在重要性，这些微生物能降解植物制成的DMSP以释放DMS。总而言之，这将确定特定的发展触发因素和环境因素(例如农业实践、土壤化学或作物生理)是否直接导致农业产生更多DMSP和向大气中释放DMS。由于我们正在挑战DMSP/DMS合成只是一个海洋过程的教条，我们还将使用数学模型重新评估DMSP/DMS的全球预算，以便可以考虑农业生产的DMSP/DMS以及任何潜在的气候冷却影响。这项工作将使我们能够更好地理解和预测农业景观对这些有影响力的化合物生产的重要性。总体而言，这项工作将使我们能够理解农业如何以及为什么对全球DMSP和DMS产量做出贡献。这将使我们能够更好地预测DMSP和DMS对自然环境、农业粮食系统和气候的影响。利用DMSP在植物中产生的保护作用和促进生长的微生物的有益特性，还可能使我们能够在压力条件下(例如，与气候变化有关的干旱和盐分)改善作物生长和生产力，并增强未来的粮食安全和气候降温DMS生产。

Billions of tonnes of the organosulfur compound dimethylsulfoniopropionate (DMSP) are made each year by marine algae, corals and bacteria, but plants also make this important molecule, including crops such as maize and tomato. DMSP is key in global sulfur cycling, as it is the main precursor of the climate-active gas dimethylsulfide (DMS). In marine settings, DMS gives the seaside its distinctive smell and is used by many animals and birds as a chemoattractant associated with their algal food. DMS is oxidised in the atmosphere to sulfates that accelerate cloud formation. These clouds affect the amount of sunlight reaching the Earth's surface and this in turn affects the climate by causing a local cooling effect. Sulfur is returned to land in the form of rain, completing the cycle.Production of DMSP and DMS is traditionally associated with marine environments and the coast. For example, saltmarshes are hotspots of DMSP/DMS synthesis and contribute up to 10% of global DMS emissions. However, new data (including our own) suggest that significant DMSP/DMS production also occurs in agricultural systems. We have recently identified many different crops that produce DMSP. DMSP production likely protects these crop from environmental stresses, such as salinity and nutrient limitations, but this has not been established. We have also found that crop rhizospheres contain more DMSP than is typically found in seawater and that they emit DMS. Moreover, we have isolated crop-associated bacteria that convert DMSP into DMS and promote plant growth. In this project, we will evaluate the importance of DMSP/DMS production in agriculture and assess whether harnessing or manipulating these processes can improve agricultural productivity, boost crop and climate-cooling DMS yields.We will study the agricultural production and turnover rates of DMSP and DMS by different crops growing in field sites over a season. By building and deploying remote DMS field sensors, we will track DMS production in real-time from crops, giving us high-resolution data on DMS release into the atmosphere from agriculture to inform models. We will also assess the abundance, diversity and potential importance of crop-interacting microbes that degrade plant-made DMSP to release DMS. Together, this will establish whether specific developmental triggers and environmental factors (e.g. agricultural practices, soil chemistry or crop physiology) cause more DMSP production and DMS release into the atmosphere as a direct result of agriculture. Since we are challenging the dogma that DMSP/DMS synthesis is solely a marine process, we will additionally reassess the global budgets for DMSP/DMS using mathematical modelling, so that DMSP/DMS production from agriculture and any potential climate cooling effects can be considered. This work will allow us to better understand and predict the significance of agricultural landscapes for the production of these influential compounds.Overall, this work will allow us to understand how and why agriculture contributes to global DMSP and DMS production. This will allow us to predict better the impacts of DMSP and DMS on the natural environment, agri-food systems and climate. Harnessing the protective effects of DMSP production in plants and the beneficial traits of growth-promoting microbes may also allow us to improve crop growth and productivity under stressful conditions (e.g. drought and salinity linked to climate change), and enhance future food security and climate-cooling DMS production.