Research advances in the plant-ectomycorrhizal fungus-bacteria tripartite system in relation to phosphorus cycling

In natural soils, phosphorus predominantly exists in stable forms such as chelated inorganic phosphorus, resulting in low levels of available phosphorus. To cope with phosphorus limitation, woody plants typically form symbiotic associations with ectomycorrhizal fungi (ECMF) to enhance phosphorus acquisition. Studies have indicated that ECMF exhibit limited capacity to directly solubilize chelated inorganic phosphorus. However, they can recruit phosphate-solubilizing bacteria in the hyphosphere by releasing specific compounds, thereby facilitating the desorption of chelated inorganic phosphorus. Nevertheless, comprehensive reviews analyzing the role of plant-ECMF-bacteria tripartite systems in phosphorus cycling remain scarce. This article introduces the conceptual framework of plant-ECMF-bacteria tripartite systems, elucidates the physiological, biochemical, and molecular mechanisms underlying phosphorus cycling among ECMF, mycorrhiza helper bacteria, and host plants, and discusses future research directions for optimizing plant phosphorus acquisition through the tripartite systems.