Abstract

Phosphate (Pi) acquisition of crops via arbuscular mycorrhizal (AM) symbiosis gains increasing importance due to limited high-grade rock Pi reserves and demand for environmentally sustainable agriculture. Mutations in either of two symbiosis-specific rice Pi transporters, PT11 and PT13 , affected fungal colonization and arbuscule formation demonstrating that both genes are essential for AM symbiosis. However, for symbiotic Pi uptake, only PT11 is necessary and sufficient. The role of PT13 remained unclear. Further investigations showed that the expression of PT13 is up-regulated by an elevated Pi status of rice roots. The PT13 promoter activity in arbusculated or innermost cortex cells suggests a function of PT13 associated with the high Pi concentration of these cells. Moreover, PT13 is predominantly expressed and required for colonization of AM fungi in the shoot-derived crown roots. These data indicated that PT13 might be responsible for the Pi distribution under high Pi conditions. To further characterize PT13 function we are currently investigating the sub-cellular localization and physiological consequences of over-expression of PT13 in Arabidopsis.