21ENGBIO - High-Throughput Design of Novel Sensors to Help Address the Impending Phosphate Crisis

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It has been predicted that over the next generation, if current trends are maintained, there will be a global shortage of phosphate, a nutrient that is critical for modern agricultural practices. This will have a severe impact on food security worldwide and has been dubbed the impending "Phosphate Crisis". Phosphate is a nutrient that is required for plant growth. It is naturally found in soil and absorbed through the roots of plants, but over time it is depleted. In agricultural settings, phosphate is added back to the soil using fertilizers. However, the phosphorus used in most fertilizers originates from finite mineral sources. To further compound this, phosphorus sources are not evenly distributed geographically, which is likely to lead to an increase in geopolitical tension as the global supply decreases. Beyond the risks posed by the limited availability of phosphate, the application of phosphate fertilizers can also lead to the pollution of water, which results in eutrophication and thus excessive algal or plant growth. This "nutrient pollution" can have a devastating impact on biodiversity and lead to significant economic costs.In order to avert the "Phosphate Crisis" and reduce the impacts of nutrient pollution, we must change our agricultural practices to optimise the use of phosphate fertilizers. The first step to doing this is to gain a better understanding of how plants utilise phosphate. The processes involved in managing phosphate usage are poorly understood due in part to a lack of sensors that can be used for real-time monitoring of phosphate levels in living plants. These sensors would illuminate how plants manage their phosphate stores and distribute it throughout the plant. Developing sensors for use in whole plants is a challenging due to the diversity of conditions in which the sensor must operate. Current sensors have limited sensitivity and are non-functional in the vacuole, which is a key subcellular phosphate reservoir.We are taking a novel approach to developing phosphate sensors, using cutting-edge protein-design methods to create and test our sensors in computer simulations before constructing the most promising candidates in the lab. We will combine known phosphate-binding proteins with sensing regions known as circularly-permuted fluorescent proteins, which will create sensors that produce light and change brightness when phosphate is present. We will construct these sensor proteins at scale, using the Edinburgh Genome Foundry, a state-of-the-art facility that can automate the construction and testing of complex biological molecules.To test our sensors and determine how they would function in plants, we will create a screen that accurately captures the cellular environments where the sensors will be applied. To do this, we will analyse the cellular composition of crop plants supplemented with various levels of phosphate and use this information to recreate these conditions in a simple screen that can be scaled up to test our sensors. We will thoroughly characterise our designed sensors and profile how they behave in a range of conditions in order to create a toolkit of sensors.All methods and data generated while designing the sensors will be made publicly available. While the sensors will have clear and important utility for studying fundamental phosphate biochemistry, they could also have important biotechnological applications. For example, they could be used to create novel plant strains that can be used to monitor phosphate in the field. This would enable farmers to apply phosphate fertilizers more efficiently, reducing phosphate usage and making sustainable sources of phosphate more viable.