Increasing nitrogen (N) fertilizer and the selection of high-yield crops have sustained our growing world population. However, the associated environmental damage is high and N application needs to be restricted while maintaining yield. Despite significant progress in our understanding of nitrogen use efficiency, a strong yield penalty remains when N supply is limiting. To address this challenge, it is essential to obtain deeper molecular insight on how N is sensed and how low N restricts growth. Multiple studies have shown that N-signaling is tightly coupled with carbon (C) levels, but how the interplay between C/N metabolism and growth is regulated remains an enigma. Nevertheless, there is a growing appreciation for the involvement of the TOR and SnRK1 kinases, two ancient master regulators that link nutrient sensing with growth. By integrating kinase activity read-outs with phosphoproteomics and interactomics, we will map N signaling in relation to C with a focus on the involvement of TOR and SnRK1. As such, we will reveal inhibitory proteins and repressive PTM sites that negatively regulate growth when the C/N balance is disturbed. Through combinatorial CRISPR screens targeted towards the mapped network, we will map genetic interactions that enhance growth under low-N supply. Finally, successful events will be selected for an in-depth molecular analysis exploring the function of the individual genes and their relation with plant growth, C/N assimilation and TOR/SnRK1.