Plastoglobules compartmentalize nitrogen assimilation in maize

Efficient nitrogen assimilation is important for sustainable agriculture1, yet its subcellular organization remains unknown. Here we show that plastoglobules (PGs) in the chloroplasts of mesophyll cells function as a metabolic hub that orchestrates nitrogen utilization in maize. Nitrogen-responsive dynamics of PGs represent a conserved feature across plant species. We identify two key enzymes, nitrite reductase 2 (ZmNIR2) and glutamine synthetase 1 (ZmGLN1), specifically targeted to PGs by a chloroplast transit peptide and hydrophobic region. Cryogenic electron microscopy analysis of recombinant ZmGLN1 shows a decameric complex, enabling a metabolon with ZmNIR2 for enhanced efficiency. Among two NIR and six GLN enzymes, ZmNIR2 and ZmGLN1 are the primary PG-localized components that orchestrate sub-organellar nitrogen assimilation and dictate nitrogen use efficiency. Genetic variation in ZmNIR2 splicing in cultivated germplasm generates a PG-targeted isoform (ZmNIR2T1) that boosts NUE. Our work establishes PGs as a central compartment for primary nitrogen assimilation, providing a promising strategy to develop high-NUE crops for global food security.