Nanjing University-Nanjing Forestry University Joint Institute for Plant Molecular Biology, School of Life Sciences, Nanjing University, Nanjing 210093, People's Republic of China.
The Key Laboratory of Western Resources Biology and Biological Technology, College of Life Sciences, Northwest University, Xi'an 710069, People's Republic of China.
Plant Physiol. 2019 Feb;179(2):640-655. doi: 10.1104/pp.18.01424. Epub 2018 Dec 14.
Vacuolar storage of phosphate (Pi) is essential for Pi homeostasis in plants. Recent studies have identified a family of vacuolar Pi transporters, VPTs (PHT5s), responsible for vacuolar sequestration of Pi. We report here that both VPT1 and VPT3 contribute to cytosol-to-vacuole Pi partitioning. Although VPT1 plays a predominant role, VPT3 is particularly important when VPT1 is absent. Our data suggested that the double mutant was more defective in Pi homeostasis than the single mutant, as indicated by Pi accumulation capacity, vacuolar Pi influx, subcellular Pi allocation, and plant adaptability to changing Pi status. The remaining member of the VPT family, VPT2 (PHT5;2), did not appear to contribute to Pi homeostasis in such assays. Particularly interesting is the finding that the double mutant was impaired in reproductive development with shortened siliques and impaired seed set under sufficient Pi, and this phenotype was not found in the and double mutants. Measurements of Pi contents revealed Pi over-accumulation in the floral organs of as compared with the wild type. Further analysis identified excess Pi in the pistil as inhibitory to pollen tube growth, and thus seed yield, in the mutant plants. Reducing the Pi levels in culture medium or mutation of PHO1, a Pi transport protein responsible for root-shoot transport, restored the seed set of Thus, VPTs, through their function in vacuolar Pi sequestration, control the fine-tuning of systemic Pi allocation, which is particularly important for reproductive development.
液泡中磷酸盐（Pi）的储存对于植物的 Pi 稳态至关重要。最近的研究已经确定了一类液泡 Pi 转运蛋白（VPTs，PHT5s），它们负责 Pi 的液泡隔离。我们在这里报告，VPT1 和 VPT3 都有助于细胞质到液泡的 Pi 分配。尽管 VPT1 起着主要作用，但当 VPT1 不存在时，VPT3 尤为重要。我们的数据表明，双突变体在 Pi 稳态方面比单突变体缺陷更大，这表现在 Pi 积累能力、液泡 Pi 内流、亚细胞 Pi 分配和植物对改变 Pi 状态的适应性上。VPT 家族的另一个成员 VPT2（PHT5;2）似乎在这些测定中对 Pi 稳态没有贡献。特别有趣的是发现，双突变体在生殖发育方面受到损害，表现为短荚果和在有足够 Pi 的情况下种子结实能力受损，而在 和 双突变体中没有发现这种表型。Pi 含量的测量显示，与野生型相比， 双突变体的花器官中 Pi 过度积累。进一步的分析表明，过量的 Pi 在雌蕊中抑制花粉管的生长，从而影响突变体植物的种子产量。在培养基中降低 Pi 水平或突变负责根到茎运输的 Pi 转运蛋白 PHO1，恢复了 双突变体的种子结实率。因此，VPTs 通过其在液泡 Pi 隔离中的功能，控制系统性 Pi 分配的微调，这对生殖发育尤为重要。
