A nitric oxide reductase is a key enzyme target for eliminating fungal emissions of nitrous oxide

Nitrous oxide (N₂O) derived from agricultural activity is a major contributor to Earth's greenhouse effect. Synthetic nitrogen fertilizer applied at high levels, particularly combined with heavy rainfall events, generates hot spots of N₂O emissions in agricultural fields due to the process of microbial denitrification. Here, a key conserved fungal denitrification enzyme necessary for N₂O emissions was identified. Phylogenetic analysis revealed that fungal NOR1-like genes, with rare exceptions, are highly conserved and confined to the phylum Ascomycota. Plant pathogenic Fusarium species that possess NOR1 exhibited drastic differences in N₂O production based on denitrification potential. Functional characterization of the p450nor nitric oxide reductase encoding gene, NOR1, in the soil-borne denitrifying maize pathogen, Fusarium verticillioides, showed that this enzyme is critical for fungal N₂O production. Deletion of the single copy NOR1 gene in F. verticillioides eliminated N₂O emissions. Complementation of deletion mutants via the NOR1 gene add-back restored wild type N₂O emission levels and segregation analysis further corroborated the pivotal role of NOR1 for N₂O emissions. We suggest targeting of the NOR1 enzyme as an effective strategy to reduce fungal-based N₂O emissions.