Soil to Cytoplasm: The Mycorrhizal Phosphorus Express and Its Regulatory Steps

Mycorrhizal symbiosis shows the most widespread evolutionarily ancient strategy by which higher plants overcome phosphorus limitations in soil. The acquisition of phosphorus by terrestrial plants is fundamentally constrained by low soil mobility and strong chemical fixation. Arbuscular mycorrhizal symbiosis overcomes these limitations through a regulated transport system that regulates phosphate movement across distinct control points such as soil extraction, internal hyphal translocation, and the host-fungal exchange interface. This review provides a mechanistic synthesis of each checkpoint, and evaluates how up- and downregulatory genes, specific phosphate transporter families, and environmental conditions collectively determine symbiotic efficiency. We integrate recent advances in molecular genetics, computational modelling, and artificial intelligence to resolve the spatial and temporal dynamics of phosphate movement from soil to plant cell. The analysis reveals that the phosphorus journey from soil to cell represents a chain of tightly regulated transport events through the multiple checkpoints. Each checkpoint dictates the regulation of phosphorus, and helps in nutrient exchange judiciously. By mapping these regulatory stops, the review establishes a comprehensive framework for the optimization of biological phosphorus acquisition. The review also determines when and why proper symbiosis fails and ways to overcome such critical feature. The synthesis identifies critical regulatory nodes and outlines targeted strategies to enhance biological phosphorus acquisition, optimize crop nutrient-use efficiency, and reduce reliance on mineral fertilizers in sustainable agricultural systems.

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