Maize (Zea mays L.) interaction with the arbuscular mycorrhizal fungus Rhizophagus irregularis allows mitigation of nitrogen deficiency stress: physiological and molecular characterization

Maize is currently the most productive cereal crop in the world ([www.faostat.org][1]). Maize can form a symbiotic relationship with the Arbuscular Mycorrhizal Fungus MF, Rhizophagus irregularis . In this relationship, the fungus provides the plant with additional water and mineral nutrients, while the plant supplies carbon compounds to the fungus. Two maize lines were studied, and they exhibited contrasting responses to AMF inoculation based on their physiological and molecular characteristics. Interestingly, the beneficial effects of the AMF were observed mainly under conditions of limited N fertilization. Under such conditions, the AMF helped maintain plant biomass production even when there was a significant reduction in N supply. The availability of nitrogen was found to be a crucial factor influencing all the traits studied. This suggests that the level of N supply plays a pivotal role in determining how the maize plants interact with the AMF. Despite the two maize lines showing different transcriptomic and metabolomic responses to R. irregularis , their agro-physiological traits remained similar. This indicates that while there may be genetic differences in how the plants respond at the molecular level, the overall growth and productivity outcomes are comparable. Both the plant and fungal transcriptomes were more significantly influenced by the level of N nutrition rather than the specific maize genotype. This suggests that N availability has a more profound impact on gene expression in both organisms than the genetic makeup of the maize plant. To understand the metabolic implications of this symbiotic relationship, we integrated transcriptomic data into a multi-organ Genome-scale metabolic model (GSM) called iZMA6517 based on a stoichiometric approach. This modelling approach highlighted nucleotide and ureides metabolism as previously unrecognized factors contributing to the symbiotic N nutrition facilitated by R. irregularis , thereby enhancing maize growth. ### Competing Interest Statement The authors have declared no competing interest. [1]: http://www.faostat.org