Integrative Multi-Omics Analysis Reveals Transcriptomic and Metabolic Remodeling Associated with Enhanced Peanut Nodulation Under Arbuscular Mycorrhizal Fungal Inoculation and Calcium Application

Peanut (Arachis hypogaea L.) yield depends on biological nitrogen fixation, but the molecular mechanisms underlying the combined effects of arbuscular mycorrhizal fungi (AMF) and calcium fertilizer on nodulation remain unclear. Here, we used integrated transcriptomic and metabolomic analyses to investigate potential mechanisms in peanut roots. Compared with the non-inoculated control, AMF inoculation alone was associated with a 22.1% higher nodule number per plant. The combined application of AMF and CaO showed a 35.9% higher nodulation than AMF alone, and a 30.9% higher AMF colonization rate than AMF alone was also observed. Mechanistically, AMF colonization was associated with enhanced carbon-nitrogen metabolic profiles and up-regulation of phenylpropanoid metabolism-related pathways, suggesting a potential role in providing energy, carbon skeletons, and signaling molecules for nodule formation. Calcium fertilizer correlated with strengthening of the glyoxylate cycle and pentose phosphate pathway, possibly contributing to the energy supply for nodulation. It also affected genes related to protein secretion and lipid metabolism, with observed changes in membrane lipids and transport metabolites, which may enhance symbiotic interface function. This study reveals the multi-level mechanisms through which AMF and calcium fertilizer collectively promote peanut nodulation, providing a systems-level perspective on plant–microbe–nutrient relationships during symbiosis. Our findings offer new insights for sustainable agriculture by reducing chemical nitrogen inputs and promoting nodulation in legumes.