Plant vacuoles serve as the primary intracellular compartments for inorganic phosphate (Pi) storage. Passage of Pi across vacuolar membranes plays a critical role in buffering the cytoplasmic Pi level against fluctuations of external Pi and metabolic activities. Here we demonstrate that the SPX-MFS proteins, designated as PHOSPHATE TRANSPORTER 5 family (PHT5), also named Vacuolar Phosphate Transporter (VPT), function as vacuolar Pi transporters. Based on (31)P-magnetic resonance spectroscopy analysis, Arabidopsis pht5;1 loss-of-function mutants accumulate less Pi and exhibit a lower vacuolar-to-cytoplasmic Pi ratio than controls. Conversely, overexpression of PHT5 leads to massive Pi sequestration into vacuoles and altered regulation of Pi starvation-responsive genes. Furthermore, we show that heterologous expression of the rice homologue OsSPX-MFS1 mediates Pi influx to yeast vacuoles. Our findings show that a group of Pi transporters in vacuolar membranes regulate cytoplasmic Pi homeostasis and are required for fitness and plant growth.

中文翻译：

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鉴定介导磷酸盐储存的植物液泡转运蛋白。

植物液泡用作无机磷酸盐（Pi）储存的主要细胞内区室。Pi穿过液泡膜的通道在缓冲细胞质Pi的水平以抵抗外部Pi的波动和代谢活性方面起着至关重要的作用。在这里，我们证明了SPX-MFS蛋白，称为PHOSPHATE TRANSPORTER 5家族（PHT5），也称为Vacuolar Phosphate Transporter（VPT），起着液泡Pi转运蛋白的作用。根据（31）P磁共振波谱分析，拟南芥pht5; 1功能丧失的突变体比对照积累的Pi少，液泡与胞质Pi的比率低。相反，PHT5的过度表达导致大量的Pi螯合成液泡并改变了Pi饥饿反应基因的调控。此外，我们显示，水稻同源物OsSPX-MFS1的异源表达介导Pi流入酵母液泡。我们的发现表明，液泡膜中的一组Pi转运蛋白调节细胞质Pi的动态平衡，是适应性和植物生长所必需的。