Research progress on crop GS-GOGAT cycle under low nitrogen stress

Nitrogen is necessary for crop growth. Following the uptake of nitrogen from the external environment, crops convert it as organic nitrogen using internal transport and metabolic processes, thereby promoting growth and development. Understanding the process of nitrogen assimilation in crops is crucial for studying the mechanisms of nitrogen metabolism and enhancing the efficient use of nitrogen in crops. This study examined the research progress, hotspots, and development trends of nitrogen assimilation under low nitrogen stress in domestic and foreign crops based on CiteSpace software, presenting a visualized analysis. The results revealed that nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), glutamate synthetase (GOGAT), and glutamate dehydrogenase (GDH) exhibit different responses under low nitrogen stress conditions. However, these enzymes are coupled and regulated at multiple levels, leading to functional differentiation among different organs. The NR activity is regulated by the dual-affinity nitrate transporter system (NRTs) and Dof1/miRNA. NiR interacts synergistically with NR to receive light-nitrogen signals and enhances stress resistance by genetically engineered targeted nitrite regulation. GDH facilitates carbon-nitrogen integration and nitrogen mobilization during senescence through isoenzyme mediation. GOGAT isoforms play a dominant role in nitrogen allocation, and their expression is regulated by the nitrogen source type and the genetic background of the species. Finally, we look forward to future research directions for crops in the field of nitrogen metabolism to provide a reference for rational nitrogen application, promote assimilate accumulation, and improve crop yield and quality.