Identification of vacuolar phosphate efflux transporters in land plants

Abstract

Inorganic phosphate (Pi) is an essential component of all life forms. Land plants acquire Pi from the soil through roots and associated symbioses, and it is then transported throughout the plant. When sufficient, excess Pi is stored in vacuoles for remobilization following Pi deficiency. Although Pi release from the vacuoles to the cytoplasm serves as a critical mechanism for plants to adapt to low-Pi stress, the transporters responsible for vacuolar Pi efflux have not been identified. Here, we identified a pair of Oryza sativa vacuolar Pi efflux transporters (OsVPE1 and OsVPE2) that were more abundant in plants grown under Pi-deficient conditions. These OsVPE proteins can transport Pi into yeast cells and Xenopus laevis oocytes. Vacuolar Pi content was higher in the loss-of-function Osvpe1Osvpe2 double mutant than in wild type, particularly under low-Pi stress. Overexpression of either OsVPE1 or OsVPE2 in transgenic plants reduced vacuolar Pi content, consistent with a role in vacuolar Pi efflux. We demonstrate that these VPE proteins evolved from an ancient plasma membrane glycerol-3-phosphate transporter protein. Together, these data indicate that this transporter was recruited to the vacuolar membrane to catalyse Pi efflux during the course of land plant evolution.

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Fig. 1: A pair of Pi starvation-induced OsVPE proteins are located on the vacuolar membrane in rice.
Fig. 2: OsVPE1 and OsVPE2 can confer Pi transport activity in yeast and X. laevis oocytes.
Fig. 3: Vacuolar Pi levels are significantly reduced in OsVPE-overexpressing plants and the efflux of vacuolar Pi in the Osvpe1Osvpe2 double mutant is partially defective.
Fig. 4: The Osvpe1Osvpe2 double mutant is stunted under Pi-replete conditions and more sensitive to Pi starvation.
Fig. 5: OsVPE1 and OsVPE2 together with the relative GlpT form a separate VPE clade and reside on the vacuolar membrane in rice.

Data availability

The data that supports the findings of this study are available within the article and its Supplementary Information files or from the corresponding authors upon reasonable request.

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Acknowledgements

The authors thank B. Menand for valuable suggestions, J. M. Thevelein for the yeast strains, and L. Jiang and G. Miesenböck for the PEpHluorin and PRpHluorin. This work was supported by the National Key Research and Development Program of China (2017YFD0200204) and the National Natural Science Foundation (31772386, 31801924 and 31670267). K.Y. was supported by the National Program for the Support of Top-notch Young Professionals and the Innovation Program of Chinese Academy of Agricultural Sciences. L.D. is funded by a European Research Council Advanced Grant (EVO-500; contract number 25028). S.L. is funded by a grant from the National Science Foundation.

Author information

K.Y. conceived and supervised the project. L.X., H.Z. and K.Y. designed the research. L.X., H.Z., R.W., Y.L., Z.X., W.T., W.R., F.W., M.D. and J.W. performed the experiments. L.X., H.Z., R.W., L.D., S.L., S.X. and K.Y. analysed the data. L.X., H.Z. and K.Y. wrote the paper with contributions from all the authors.

Correspondence to Shaowu Xue or Keke Yi.

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