Functional analysis of NLP7 for optimising nitrate responsive growth

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Plants use nutrients from the soil, energy from sunlight, and air and water to produce all the metabolites they need for growth. In turn plants provide, directly and indirectly, essentially all of the nutrients that sustain humans. Nutrient acquisition from the soil requires special proteins called transporters that can take up trace levels of nutrients from the soil. Because soil composition varies, plants adapt their growth requirements to nutrient availability by altering the levels and activities of nutrient transporters so that plant growth is optimised even though nutrient levels change. Much has been learnt about the mechanisms involved in controlling nitrate uptake and utilisation for growth because it has a key bearing on the application of fertilisers. The high yields of crops are critically dependent on the application of high levels of fertilisers such as NPK to supply the main nutrients. About 1/3 of applied nitrogenous fertiliser is actually taken up and used by the plant, with the rest remaining bound in the soil or washed away into watercourses, where it is a major pollutant. Consequently the application of nitrate-containing fertilisers is limited by legislation, and may need to be reduced further. However, many modern crop varieties have been bred to produce high yields in response to high nitrate applications. Therefore we need to breed new crop varieties that can maintain high levels of productivity in relatively low nitrate levels. One way of approaching this challenge is to understand precisely how plants respond to nitrate levels in the soil and programme their metabolism and growth to take up and metabolise nitrate for growth. We have recently identified a genetic switch that coordinates this response. We have shown that this switch requires both nitrate and sugars to work, and that it may provide a way for plants to coordinate the supply of nitrate from the soil and energy and carbohydrates from photosynthesis to make nutrients for growth. In this research project we aim to understand this switch in a precise quantitative way, and then to subtly alter components to see if we can make a switch that has different quantitative responses to nitrate and sugar levels. We will then test if this alters plant growth responses to nitrate and illumination levels. In this way the proposed research will provide new knowledge and understanding that can be used to create new crop varieties that can grow and produce good yields from reduced inputs of fertilisers. This will help achieve more environmentally sustainable agricultural production systems for major crops.