Xu, G.-H., State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China
Chague, V., Plant Science Department, Weizmann Institute of Science, Rehovot 76100, Israel
Melamed-Bessudo, C., Plant Science Department, Weizmann Institute of Science, Rehovot 76100, Israel
Kapulnik, Y., Plant Department, ARO, Volcani Center, Bet Dagan 50250, Israel
Jain, A., Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN 47907, United States
Raghothama, K.G., Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN 47907, United States
Levy, A.A., Plant Science Department, Weizmann Institute of Science, Rehovot 76100, Israel
Silber, A., Institute of Soil, Water and Environmental Science, Volcani Center, Bet Dagan 50250, Israel

Many plant roots acquire inorganic phosphate (Pi) from soils directly through the root-soil interface via high-affinity Pi transporters and/or through symbiotic associations between the cortical cells and arbuscular mycorrhizal fungi. In tomato, three phosphate transporters (LePT3, LePT4, and LePT5) are up-regulated upon colonization by arbuscular mycorrhizal fungi. In this study, the role of LePT4 in tomato is elucidated by molecular and physiological characterizations of a loss-of-function mutant lept4. In the absence of mycorrhizal infection and under solution-Pi concentrations (Cp) of 0.05 mM and 0.5 mM, the mutant exhibited severe Pi-deficiency symptoms which were associated with significantly lower Pi uptake as compared with that of the wild type. However, at a Cp of 5 mM, lept4 grew better than the wild type. Mycorrhizal infection at a Cp of 0.05 mM resulted in a significant increase in the transcripts of LePT4 in the wild type and a concomitant 2-fold increase in Pi uptake. Although upon mycorrhizal infection, lept4 also exhibited an increased Pi uptake, it was significantly lower than that of the wild type. Under a Cp of 1 mM and in the absence of mycorrhizal infection, LePT4 expression was suppressed in the wild type and a mutation in this gene resulted in a slight reduction in total Pi uptake. These data highlight the pivotal role of LePT4 in mycorrhizal-mediated Pi uptake in tomato, and show that this function may not be fully compensated by other members of the family. Characterization of the mycorrhiza-associated Pi transporter lept4 mutant, along with expression analysis of LePT3, provides evidence for the different routes of mycorrhiza-mediated Pi uptake in plants. © 2007 The Author(s).