Arbuscular mycorrhizal fungi potentially regulate N2O emissions from agricultural soils via altered expression of denitrification genes

Highlights: • AMF showed potentials to reduce N₂O emissions from agricultural soils. • AMF can alter relative abundances of nirK and nosZ in agricultural soils. • SEM suggested effects of AMF on genes involved in denitrification and N₂O emission. Agricultural soils are an important source of nitrous oxide (N₂O), a potent greenhouse gas involved in the destruction of the protective ozone layer that contributes to global warming. During N₂O production, soil microorganisms play important driving and regulating roles. A few recent studies have revealed the potential effects of arbuscular mycorrhizal fungi (AMF), a widely distributed soil fungi, on controlling N₂O emissions. However, how AMF regulate N₂O production from soils remains poorly understood. To address the knowledge gap, we manipulated two independent soil environments, which were either allowed (AM) or prevented (NM) access by AMF hyphae in a microcosm experiment (n = 5). Soil physicochemical properties, N₂O flux, the diversity of bacterial communities, and the abundance of key genes responsible for N₂O production were assessed in both treatments over three months. Results showed that the presence of AMF significantly decreased N₂O emissions from agricultural soils in the 1st month, and the abundance of key genes responsible for denitrification (nirK and nosZ) significantly decreased in AM treatments, indicating that the regulation of N₂O emissions is transmitted by AMF-induced changes in the denitrification process. A structural equation model further revealed that AMF indirectly influenced N₂O emissions by altering the abundance of N metabolism-related genes, rather than by altering soil chemical properties or the diversity of bacterial communities. Thus, we proposed a possible mechanism by which AMF can regulate denitrification activities and therefore N₂O emissions from agricultural soils.