An N-fix in time: circadian control of nodulation

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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.