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

海洋藻类、珊瑚和细菌每年产生数十亿吨有机硫化合物二甲基磺丙酸酯（DMSP），但植物也会产生这种重要的分子，包括玉米和番茄等作物。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赋予海边独特的气味，被许多动物和鸟类用作与其藻类食物相关的化学引诱剂。DMS在大气中被氧化成硫酸盐，加速云的形成。这些云影响到达地球表面的阳光的数量，这反过来又通过引起局部冷却效应来影响气候。硫以雨的形式返回陆地，完成这个循环。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，大量的DMSP/DMS生产也发生在农业系统中。我们最近发现了许多不同的能产生DMSP的作物。DMSP的生产可能会保护这些作物免受环境胁迫，如盐度和营养限制，但这一点尚未得到证实。我们还发现，作物根际比海水中通常发现的DMSP含量更多，而且它们会释放DMS。此外，我们已经分离出将DMSP转化为DMS并促进植物生长的作物相关细菌。在本项目中，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，提高作物和气候冷却DMS产量。我们将研究不同作物在一个季节内田间种植的DMSP和DMS的农业产量和周转率。通过建立和部署远程DMS田间传感器，我们将实时跟踪作物的DMS生产，为我们提供农业向大气中释放DMS的高分辨率数据，以告知模型。我们还将评估作物相互作用微生物的丰度、多样性和潜在重要性，这些微生物可以降解植物制造的DMSP以释放DMS。总之，这将确定特定的发育触发因素和环境因素（如农业实践、土壤化学或作物生理）是否会导致DMSP的生产和DMS释放到大气中，这是农业的直接结果。由于我们正在挑战DMSP/DMS合成仅仅是一个海洋过程的教条，我们将使用数学模型重新评估DMSP/DMS的全球预算，因此可以考虑农业DMSP/DMS生产和任何潜在的气候冷却效应。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的化合物生产的意义。总的来说，这项工作将使我们能够了解农业如何以及为什么对全球DMSP和DMS生产做出贡献。这将使我们能够更好地预测DMSP和DMS对自然环境、农业食品系统和气候的影响。利用植物DMSP生产的保护作用和促进生长的微生物的有益特性，还可以使我们在逆境条件下（例如与气候变化有关的干旱和盐度）改善作物生长和生产力，并加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.