Abstract
Plant phosphate transporters (PTs) are active in the uptake of inorganic phosphate (Pi) from the soil and its translocation within the plant. Here, we report on the biological properties and physiological roles of OsPht1;8 (OsPT8), one of the PTs belonging to the Pht1 family in rice (Oryza sativa). Expression of a β-glucuronidase and green fluorescent protein reporter gene driven by the OsPT8 promoter showed that OsPT8 is expressed in various tissue organs from roots to seeds independent of Pi supply. OsPT8 was able to complement a yeast Pi-uptake mutant and increase Pi accumulation of Xenopus laevis oocytes when supplied with micromolar (33)Pi concentrations at their external solution, indicating that it has a high affinity for Pi transport. Overexpression of OsPT8 resulted in excessive Pi in both roots and shoots and Pi toxic symptoms under the high-Pi supply condition. In contrast, knockdown of OsPT8 by RNA interference decreased Pi uptake and plant growth under both high- and low-Pi conditions. Moreover, OsPT8 suppression resulted in an increase of phosphorus content in the panicle axis and in a decrease of phosphorus content in unfilled grain hulls, accompanied by lower seed-setting rate. Altogether, our data suggest that OsPT8 is involved in Pi homeostasis in rice and is critical for plant growth and development.
Highlights
Plant phosphate transporters (PTs) are active in the uptake of inorganic phosphate (Pi) from the soil and its translocation within the plant
Our results showed that the expression of OsPT8 was abundantly expressed in roots and moderately in shoots grown in Pi-sufficient solution
Plants acquire Pi by its active uptake into the epidermal and cortical cells of the root via the H+/Pi symporters of the Pht1 family (Raghothama, 2000; Poirier and Bucher, 2002)
Summary
Plant phosphate transporters (PTs) are active in the uptake of inorganic phosphate (Pi) from the soil and its translocation within the plant. Thirteen putative high-affinity Pi transporter genes belonging to the Pht family (OsPT1–OsPT13) have been identified in the rice (Oryza sativa) genome (Goff et al, 2002). We demonstrated that two Pi starvation-responsive Pht members in rice, OsPT2 and OsPT6, have different functions and kinetic properties in Pi uptake and translocation (Ai et al, 2009). OsPT2, unlike other Pht members, is a low-affinity Pi transporter that might mainly play roles during the Pi translocation process (Ai et al, 2009). Overexpession of OsPT2 can cause overaccumulation of shoot Pi in rice and a Pi toxicity phenotype (Liu et al, 2010)
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