Understanding the interaction between an organism and its environment is crucial, and is particularly relevant in relation to plants since they are unable to move around yet must also cope with environmental extremes. Perhaps as a consequence of their sessile nature plants exhibit a large degree of developmental plasticity: they are capable of responding to even small changes in the environment by modifying their body plan in order to better cope with new conditions.
The response of the plant root to the nutrient nitrogen is an ideal model to study how an organ reacts to environmental change because nitrogen is a limiting resource for plants and one of the root's critical functions is the uptake of nitrogen from the soil.Billions are spent each year to provide nitrogen fertiliser to sustain crop species in nitrogen-poor soils. Much of this nitrogen is lost due to inefficient uptake by plants, with negative consequences on the surrounding rivers due to contamination of water runoff with nitrates and ammonia from fertilised agricultural land.
In order to understand the response to nitrogen we are looking in more detail than the organ level (roots or shoots) - we are probing individual cells. This is important since the organs of multicellular species like plants are comprised of specialised cell types that must function together to perform specific tasks.It follows then that specific cells are likely to respond differently to the same environmental change. Discovering how each different cell type responds individually to nitrogen enables us to understand both how genetic pathways controlling development change in single cells, and how cells coordinate responses to influx of a new resource amongst themselves. Using highly sensitive novel techniques we have uncovered a vast and predominantly cell-specific response that has largely been hidden from previous whole organ analyses. We also discovered a genetic circuit that controls a dramatic shift in root architecture according to nitrogen influx in a single cell type. Our findings will help to improve nitrogen use by plants, thus this work has broad potential applications for agriculture and human health.