Intracellular Inorganic Orthophosphate Distribution in Arbuscular Mycorrhizal Root

Phosphate is an essential macronutrient for plants and plays a key role in the establishment and regulation of arbuscular mycorrhizal (AM) symbiosis. However, conventional methods for studying phosphate levels in plant tissues often lack cellular resolution or require technically demanding procedures such as genetic transformation. Here, we present an adaptation of the recently developed inorganic orthophosphate staining assay (IOSA), for Lotus japonicus roots colonized by the AM fungus Rhizophagus irregularis. IOSA is a rapid, colorimetric method that enables high-resolution, semi-quantitative visualization of intracellular inorganic phosphate. This protocol provides an efficient, accessible, and genetic transformation-free approach for investigating phosphate homeostasis and its involvement in AM symbiosis, offering a valuable tool for research in plant nutrition and symbiotic interactions.