Nitrogen‐Centric Molecular Mechanisms in Crop Plants Under Elevated CO2: Interactions, Responses, and Implications

Abstract

Increasing atmospheric carbon dioxide (CO2) is transforming the climate space in which plants grow, severely affecting crop physiology and crop productivity. Elevated CO2 enhances photosynthesis and biomass; however, it can nitrogen (N) metabolism, inhibiting the nutritional value and the yield capacity of crops. The most important central N‐regulated protein machineries are: transporters, nitrate reductase, nitrite reductase, glutamine synthetase, glutamate synthase, glutamate dehydrogenase, and urease which control N assimilation, distribution and remobilization in crop plants. With high CO2, these molecular components exhibit altered expression and activities mostly due to the reduction in N concentration. Complex systemic plant responses under N control like adaptation of photosynthetic capacity, flowering time, reproductive development and seed nutrient profiles further support the complexity of the interactions between C and N signaling. The high CO2 environment requires a more holistic analysis of the regulatory networks of N metabolism and anticipative crop improvement strategies. Future breeding and crop improvement strategies should focus on enhancing the resilience of N assimilation by optimizing the N transporter function and maintaining C–N stoichiometry, thereby sustaining crop performance and nutritive quality under changing climatic conditions. The present review identifies the molecular processes that regulate N responses in crops grown under elevated CO2, highlighting the differences between legume versus non‐legume and C3 versus C4 plant responses and providing details that can ensure mitigation against negative impacts and outline future perspectives on crop improvement.