Phosphate transporters in arbuscular mycorrhizal symbiosis

In the arbuscular mycorrhizal (AM) symbiosis the reciprocal exchange of nutrients results in a nutritional benefit for both symbionts. The fungus acquires carbon from plant and the plant obtains mineral nutrients from the fungus. While there is evidence for the transfer of phosphorus (P), nitrogen, zinc and copper, current data suggest that P is transferred in the highest quantities and that symbiotic P transfer occurs in the vast majority of AM symbioses. Symbiotic phosphate Pi transfer requires transport proteins to move Pi across the membranes of the AM fungus and plant. In recent years, there has been tremendous progress in the identification of plant and fungal Pi transporter proteins involved in symbiotic Pi transport. Coupled with the physiological data a greater understanding of symbiotic Pi transfer has emerged. Here we summarize the current data about Pi transporters and their expression patterns and roles in AM symbiosis.