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Integrative regulatory networks modulating arbuscular mycorrhizal symbiosis
Arbuscular mycorrhizal symbiosis plays a pivotal role in nutrient acquisition and stress tolerance, making its regulation crucial for sustainable crop productivity. This review synthesizes current advances in understanding the molecular and physiological factors governing AM symbiosis, with emphasis on transcriptional, hormonal, and nutrient-mediated regulation. From pre-symbiotic signaling to root colonization and arbuscule development, AM formation is orchestrated by a complex network of molecular interactions. Transcription factors, including those with GRAS domains (e.g., NSP1, NSP2, RAM1, and DELLA), and other regulators such as MYB, SPX, WRKY, and CYCLOPS/IPD3, serve as central modulators of symbiosis-related gene expression. Phytohormones, including strigolactones, salicylic acid, and abscisic acid, generally promote symbiosis, whereas gibberellins and ethylene act as inhibitors; cytokinin exerts context-dependent effects. Nutrient status also modulates AM formation—low phosphorus and nitrogen promote, while high nutrient availability suppresses colonization. Collectively, these insights reveal the integrative regulatory networks driving AM symbiosis and offer new avenues to optimize symbiotic efficiency for enhanced plant growth and agricultural sustainability.