Synthetic fertilizers composed of the macronutrient's nitrogen, phosphorous, and potassium are used to improve agricultural yield across the world. Converse to the benefits of fertilizer usage, the production and application of it can have a negative environmental impact. The components used to make fertilizer can be non-renewable resources, energy intensive to acquire, or both. The application and transport of fertilizers emits greenhouse gases, and once applied to the crop, fertilizers may leach into and contaminate water systems (Krein et al. 2023). The ‘negatives’ of synthetic fertilizer use have been amplified over time, as its production has increased globally (Brownlie et al. 2024).

The problem: To reach a ‘happy medium’ where agricultural productivity and the environmental impact of fertilizer use are balanced, fertilizer should only be used when it is needed and should only be applied specifically to supplement what is deficient. This ‘happy medium’ requires a detection system that can report in real-time when the plants themselves are experiencing scarcity.

The solution: In order to create sensors capable of monitoring the availability of macronutrients in soil, transgenic plants expressing promoter-reporter gene fusions will be created. Promoters that respond to low macronutrient availability will be fused to an ultraviolet light-excitable fluorescent reporter. As a result, when there is a macronutrient deficiency, the promoter will increase the expression of the fluorescent reporter, which can then be visualized in the plant. As an initial proof of concept, the sensors will be transiently transformed into Nicotiana benthamiana and stably transformed into Arabidopsis thaliana.

Future Outlook: Sensor plants can be used to study nutrient deficiency and may also be grown alongside crop plants to monitor macronutrient availability in the field.