Abstract
A number of phosphate (Pi) starvation- or mycorrhiza-regulated Pi transporters belonging to the Pht1 family have been functionally characterized in several plant species, whereas functions of the Pi transporters that are not regulated by changes in Pi supply are lacking. In this study, we show that rice (Oryza sativa) Pht1;1 (OsPT1), one of the 13 Pht1 Pi transporters in rice, was expressed abundantly and constitutively in various cell types of both roots and shoots. OsPT1 was able to complement the proton-coupled Pi transporter activities in a yeast mutant defective in Pi uptake. Transgenic plants of OsPT1 overexpression lines and RNA interference knockdown lines contained significantly higher and lower phosphorus concentrations, respectively, compared with the wild-type control in Pi-sufficient shoots. These responses of the transgenic plants to Pi supply were further confirmed by the changes in depolarization of root cell membrane potential, root hair occurrence, (33)P uptake rate and transportation, as well as phosphorus accumulation in young leaves at Pi-sufficient levels. Furthermore, OsPT1 expression was strongly enhanced by the mutation of Phosphate Overaccumulator2 (OsPHO2) but not by Phosphate Starvation Response2, indicating that OsPT1 is involved in the OsPHO2-regulated Pi pathway. These results indicate that OsPT1 is a key member of the Pht1 family involved in Pi uptake and translocation in rice under Pi-replete conditions.
Highlights
State Key Laboratory of Crop Genetics and Germplasm Enhancement, Key Laboratory of Plant Nutrition and Fertilization in Low-Middle Reaches of the Yangtze River, Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China
Nagarajan et al (2011) reported that the Arabidopsis pht1;5-1 mutant had higher shoot P content compared with the wild type, while the P content in roots was reduced under Pi-replete conditions, suggesting that Pht1;5 may mobilize Pi between source and sink tissues
The expression of OsPT1 in roots and the root-shoot junctions was seen in epidermal cells, which are the dominant sites for the uptake of Pi from soil solution, and throughout the cortical and stele cells (Fig. 1B, a–d and g–j), suggesting that it functions in both Pi uptake and translocation in rice
Summary
State Key Laboratory of Crop Genetics and Germplasm Enhancement, Key Laboratory of Plant Nutrition and Fertilization in Low-Middle Reaches of the Yangtze River, Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, China. Transgenic plants of OsPT1 overexpression lines and RNA interference knockdown lines contained significantly higher and lower phosphorus concentrations, respectively, compared with the wild-type control in Pi-sufficient shoots These responses of the transgenic plants to Pi supply were further confirmed by the changes in depolarization of root cell membrane potential, root hair occurrence, 33P uptake rate and transportation, as well as phosphorus accumulation in young leaves at Pi-sufficient levels. OsPT1 expression was strongly enhanced by the mutation of Phosphate Overaccumulator (OsPHO2) but not by Phosphate Starvation Response, indicating that OsPT1 is involved in the OsPHO2-regulated Pi pathway These results indicate that OsPT1 is a key member of the Pht family involved in Pi uptake and translocation in rice under Pi-replete conditions. We detected that another Pi-regulated Pht member, OsPT8, is expressed in various tissues and organs and is involved in Pi homeostasis in rice (Jia et al, 2011)
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