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<正>A plant genome commonly contains several paralog genes encoding phosphate transporters（PiT） in Pht1 family.Most of them characterized so far response to either highly Pi deprivation or mycorrhiza inoculation.In this study,we detected that OsPht1;1 of Pht1 family in rice is expressed abundantly and constitutively at the transcriptional level in both roots and leaves irrespective Pi supply status.This expression pattern was confirmed by analyses of RT-PCR,in situ hybridization and transgenic rice expressing the GUS reporter gene driven by OsPht1;1-promoter. Functional complementation analyses both in yeast and oocyte systems indicated that OsPht1;1 functions as a nH+/Pi co-transporter with relative moderate Pi affinity.The transgenic plants of its overexpression（OsPht1;1-Ox） and knockdown mutant by RNA-interference（OsPht1;1-Ri） contained significant higher and lower P concentration than wild type（WT）,respectively,in Pi replete shoots,but their P concentrations in Pi-deficient shoots were similar to those in WT.There were no significant differences of P concentrations in their roots either at Pi sufficient or depleted condition.The finding was further supported by the change of 33P uptake,depolarization of root cell membrane potential and root hair occurrences at Pi-sufficient level.OsPht1;1 expression was enhanced strongly by mutation of OsPHO2（Pi Overaccumulator 2）,but not by mutation of OsPHR2 （Pi Starvation Response 2）,indicating that OsPht1;1 is negatively regulated by OsPHO2,not on the pathway regulated by OsPHR2.These results indicate that OsPht1;1 modulates Pi homeostasis in the Pi replete shoots of rice.