Abstract
PHOSPHATE TRANSPORTER TRAFFIC FACILITATOR1 (PHF1) is known to regulate the plasma membrane localization of PHT1;1, a high-affinity inorganic phosphate (Pi) transporter in Arabidopsis (Arabidopsis thaliana). OsPHF1, a rice (Oryza sativa) gene homologous to AtPHF1, was isolated and found to regulate the localization of both low- and high-affinity Pi transporters to the plasma membrane. Three OsPHF1 allelic mutants carrying one-point mutations at the fifth WD-repeat motif and two at the transmembrane helix, respectively, showed arsenate resistance and severely reduced Pi accumulation. The data indicate that mutation of OsPHF1 results in the endoplasmic reticulum retention of the low-affinity Pi transporter OsPT2 and high-affinity Pi transporter OsPT8. Mutation of OsPHF1 also reduced Pi accumulation in plants exhibiting excessive shoot Pi accumulation due to the overexpression of OsPHR2. However, the transcript level of OsPHF1 itself is not controlled by OsPHR2. Overexpression of OsPHF1 increased Pi accumulation in both roots and shoots in a solution culture with Pi-supplied condition. These results indicate that the role of OsPHF1 is unique in the localization of both low- and high-affinity Pi transporters on the plasma membrane in rice and determines Pi uptake and translocation in rice. The similar function of PHF1 required to facilitate PHT1 transit through the endoplasmic reticulum between Arabidopsis and rice provides an example of expectations from what one would deduce from sequence comparisons to extend knowledge from Arabidopsis to crops.
Highlights
PHOSPHATE TRANSPORTER TRAFFIC FACILITATOR1 (PHF1) is known to regulate the plasma membrane localization of PHOSPHATE TRANSPORTER1 (PHT1);1, a high-affinity inorganic phosphate (Pi) transporter in Arabidopsis (Arabidopsis thaliana)
The results showed that the Pi concentration in the transgenic plants was rescued to the level of the wild-type plants, which confirms that the impairment of Pi uptake ability in phf1-1 is caused by the functional loss of OsPHF1
The results showed that the overexpression of OsPHF1 leads to a Pi excessive accumulation in both leaves and roots by about 3-fold of Pi concentration compared to wild type (Fig. 3, F and G)
Summary
PHOSPHATE TRANSPORTER TRAFFIC FACILITATOR1 (PHF1) is known to regulate the plasma membrane localization of PHT1;1, a high-affinity inorganic phosphate (Pi) transporter in Arabidopsis (Arabidopsis thaliana). Overexpression of OsPHF1 increased Pi accumulation in both roots and shoots in a solution culture with Pi-supplied condition These results indicate that the role of OsPHF1 is unique in the localization of both low- and high-affinity Pi transporters on the plasma membrane in rice and determines Pi uptake and translocation in rice. Overexpression of OsPT2 and OsPT8 causes excessive shoot Pi accumulation and results in a Pi toxicity phenotype, similar to the overexpression of OsPHR2 (Liu et al, 2010; Jia et al, 2011). These reports indicate that low- and high-affinity Pi transporters in plants and yeast may possess similar phosphate uptake capacities
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