Nitrogen-responsive transcription factor kinetics meter plant growth.

The wealth of data provided by large-scale -omics studies empowers the discovery of gene regulatory networks and molecular mechanisms that underlie specific phenotypes. Most transcriptomic studies provide a snapshot of how organisms interact with their environment, recording change after a given time or in response to a single environmental variable. Organisms have not evolved in binary states of treatment vs. control and instead experience a continuum of environmental states, from optimal growth conditions to mild and ultimately severe stress. Organismal phenotypes vary along this continuum, but how molecular responses are metered to influence these phenotypes is poorly understood. In PNAS, Swift et al. (1) provide a deeper understanding of plant adaptations to nitrogen (N) availability by investigating how plant root transcriptomes change in response to varying N concentration over time. Their work on Arabidopsis thaliana not only provides a more nuanced understanding of how plants sense and appropriately adjust their metabolism to different N levels, it establishes a predictive framework for identifying critical components of N responses that can be targets for crop improvement. N is an essential nutrient found in many macromolecules. Plant roots acquire bioavailable N as nitrate or ammonium and assimilate N from these inorganic molecules into amino acids for use in protein synthesis, as well as the synthesis of nucleic acids, chlorophyll, and other secondary metabolites throughout the plant (2). N, however, is a commonly limiting nutrient in crop production, leading to the widespread amendment of soil with mineral N fertilizers. Nearly 120 Tg of N as ammonium fertilizers is produced annually (3), and their application has greatly improved crop yield and food security (4). N fertilizers, however, are both costly and significant environmental pollutants as their application generates greenhouse gas emissions, promotes acid rain, contaminates groundwater reservoirs, and causes eutrophication of freshwater and estuarine ecosystems … [↵][1]1To whom correspondence may be addressed. Email: serres{at}ucr.edu. [1]: #xref-corresp-1-1