An N-fix in time: circadian control of nodulation

植物、动物和微生物的生长发育都受到一个24小时的生物钟的控制，这个生物钟使它们能够根据环境条件的昼夜变化来协调它们的活动。昼夜节律钟设定了细胞和生物体在任何时候产生、使用和移动的重要分子的数量。当植物和微生物在共生关系中一起工作时，生物之间分子运动的时机至关重要，因为在错误的时间接受它们意味着这些重要的资源将无法有效利用。随着世界人口的持续增长，到2050年，我们需要多生产60%的粮食。作物产量必须在不增加昂贵且环境代价高昂的化肥施用的情况下增加，以向枯竭的土壤提供氮等养分，因此研究如何在植物中最大限度地利用资源是至关重要的。一个例子是豆类（例如豌豆、黄豆和小扁豆）和根瘤菌（一种固氮细菌）之间的共生关系。根瘤菌固定大气中的氮，并以硝酸盐的形式将其传递给植物宿主，从而减少对氮肥的需求。由于大多数土壤缺乏氮肥，而生产氮肥在能源和环境上都非常昂贵，因此这种共生关系在农业中至关重要。豆类也是人类和动物膳食蛋白质的重要来源。任何我们可以增强或改善结瘤影响的方法都将有助于使豆类成为更有用的作物，帮助我们实现可持续的粮食生产方式。我们已经发现，植物生物钟中被称为CCA1的部分影响了这种共生关系的建立。在这个项目中，我们将确定受时钟影响的共生的具体阶段。我们将测试CCA1的作用是否与其在时钟计时机制中的功能有关，以及可能受其影响的分子的作用。我们还将测试CCA1和植物昼夜节律在根瘤菌共生体和植物寄主之间的相容性中的作用。这项研究将使我们能够设计出生物技术治疗方法，通过与植物的生物钟合作，在未来改善结瘤。

Growth and development of plants, animals and microbes are under the control of a 24-hour biological clock known as the circadian clock, which enables them to coordinate their activities with diurnal changes in environmental conditions. The circadian clock sets in train how many important molecules are made, used and moved around cells and organisms at any time. When plants and microbes work together in symbiosis the timing of this movement of molecules between organisms is of key importance, because receiving them at the wrong time means that these important resources will not be utilised efficiently. As the world's population continues to grow we will need to produce 60% more food by 2050. Crop yields must increase without increasing expensive and environmentally costly fertiliser application to supply depleted soils with nutrients such as nitrogen and therefore research to understand how resource use can be maximized in plants is crucial.One example is the symbiosis between legumes (peas, beans and lentils for example) and rhizobium, a nitrogen-fixing bacterium. Rhizobium fixes nitrogen from the atmosphere and passes it on to its plant host in the form of nitrate, thus reducing the need for nitrogen fertiliser. Since most soils are nitrogen-poor and the production of nitrogen fertiliser is incredibly energy- and environmentally-expensive, this symbiosis is crucial in agriculture. Legumes are also an important source of dietary protein for both humans and animals. Any way that we can enhance or improve the impact of nodulation would help to make legumes an even more useful crop to help us achieve sustainable ways of producing food.We have discovered that part of the plant circadian clock called CCA1 affects the setting up of this symbiosis. In this project we will identify the specific stages of symbiosis that are affected by the clock. We will test whether the effects of CCA1 are linked to its function in the timing mechanism of the clock, and the role of molecules that might be affected by this. We will also test the role of CCA1 and of plant circadian rhythms in compatibility between the rhizobia symbiont and plant host. Together this research will enable us to design biotechnological treatments to improve nodulation in the future by working with the biological clock of the plant.