Differential modulation of rhizosphere dissimilatory nitrate reduction to ammonium (DNRA) by wheat cultivars under nitrogen deficiency

Nitrogen (N) deficiency constrains crop growth, which could potentially be mitigated by the plant-microbe interaction. However, the interaction between wheat and bacterial N metabolism in response to N deficiency remains poorly understood. A glasshouse experiment was conducted to investigate the rhizosphere bacterial N metabolism gene profile in the wheat rhizosphere with (+ N ) and without (-N) N application. Two wheat cultivars, Mace and Gladius, with contrasting reported N use efficiencies (NUE), were grown in an agriculture soil previously cropped with wheat. Metagenomic analysis, was used to examine the N metabolism gene profile of rhizobacteria under different N treatments. The result highlighted a significant difference in the rhizosphere bacterial N metabolism gene composition between Mace and Gladius. Differential abundance analysis revealed a significantly higher gene abundance involved in dissimilatory nitrate reduction to ammonium (DNRA) ( nrfA, nrfD , and nrfH ), in Mace under N deficiency. In contrast, no significant changes were found in Gladius. Correlation analysis highlighted a significant negative correlation between the abundance of nrfA and nrfH genes and plant total N content. We found that under N deficiency, Mace demonstrated a higher capacity for DNRA, consistent with its reported NUE. Our findings provide important information that the rhizosphere bacterial DNRA pathway response to N deficiency is different between wheat cultivars.