水稻液泡膜磷酸转运体调控液泡磷素平衡的分子机制研究

Phosphorus is an essential macro nutrition for crop production. Under phosphorus deficient condition, the growth of rice is significantly inhibited, which lead to a dramatic reduction of yield. The amount of phosphorus in the soil that is available to the plant is often limiting for growth, phosphorus deficiency in arable land has become a limiting factor in modern agricultural production. Plant vacuoles serve as the primary intracellular compartments for inorganic phosphate storage, analysis of the regulation mechanism by which phosphate is translocated across vacuolar membranes can help us understand the process of phosphate storage and reutilization in plants, and provide a theoretical basis for efficient utilization of phosphorus in rice production. By proteomics method (iTRAQ), we identified two vacuolar membrane localized proteins, OsVPE1 and OsVPE2, which were induced by phosphorus starvation. Vacuolar Pi concentrations in the OsVPEs overexpression lines were reduced compared to level in the wild type, while vacuolar Pi concentrations in the OsVPEs mutants were significantly higher. Furthermore the phosphate distribution between the old and young leaves were changed in the OsVPEs overexpression lines. Future analysis of the OsVPE1, OsVPE2 and previously reported SPX-MFSs proteins will provide new insight into the mechanism by which Pi is translocated across vacuolar membranes and allocated from the old to young leaves.

磷素是作物生产所必须的大量营养元素。磷素匮乏会影响水稻生长，最终导致水稻产量降低。土壤中能被植物利用的有效磷含量很低，耕地土壤缺磷已经成为现代农业生产中的限制因素。液泡是无机磷在植物细胞内的主要储存场所,解析液泡磷素运输的调控机制不仅能够帮助了解磷素在植物体内的储存及再利用过程，还能为水稻生产过程中的磷素高效利用提供理论依据。本课题组利用蛋白质组学的方法（iTRAQ）筛选出两个受磷饥饿诱导的液泡膜蛋白OsVPE1和OsVPE2。初步分析发现OsVPEs过表达后导致水稻液泡内无机磷含量下降，而OsVPEs功能失活突变体液泡内无机磷含量升高。OsVPEs过表达后还导致老叶和新叶中的磷素分配发生改变。因此，本研究将围绕OsVPE1和OsVPE2参与的液泡磷素运输机制以及磷素从老叶向新叶分配的机制，同时结合之前报道的可能参与液泡磷素转运的OsSPX-MFS基因家族，探讨水稻液泡磷素养分平衡的机制。

磷是生物体所必需的营养元素。液泡是无机磷在植物细胞内的主要储存场所,解析液泡磷素运输的调控机制不仅能够帮助了解磷素在植物体内的储存及再利用过程，还能为水稻生产过程中的磷素高效利用提供理论依据。本课题组利用蛋白质组学的方法（iTRAQ）筛选出两个受磷饥饿诱导的液泡膜蛋白OsVPE1和OsVPE2。利用qRT-PCR方法，发现OsVPE1和OVPE2在转录水平也受磷饥饿诱导。为了研究这连个基因的表达模式，利用基因组片段融合GUS报告基因的转基因植株，GUS染色结果表明，这两个基因的蛋白水平受到缺磷胁迫诱导。为了进一步研究它们的功能，我们创制了相关的转基因材料。结果表明这两个基因的增强表达植株无机磷含量及液泡磷含量下降,而这两个基因突变后无机磷含量及液泡磷含量升高。我们获得了双突材料进行分析发现，其地上部和根里无机磷浓度及液泡磷浓度更高。且在低磷胁迫条件下，双突变植株的液泡内的无机磷下降速度变缓慢，甚至在在长期缺磷的条件下，双突植株中液泡磷仍可维持在1.1 mol Pi/g。这些结果表明OsVPE1和OVPE2参与低磷条件下液泡中储存磷的输出。我们还利用酵母磷转运体缺失的突变体和电生理技术，进一步证明OsVPEs蛋白能够介导细胞中磷的运输。综上所述，我们的结果表明OsVPE1和OVPE2是负责水稻低磷胁迫下液泡磷输出的转运体。.本研究还明确了OsSPX-MFS1和OsSPX-MFS3的功能是将细胞质中的无机磷运输到液泡中。进一步研究发现，OsVPEs和OsSPX-MFSs家族基因都参与调控了无机磷从老叶向新叶的分配过程。适当增强表达OsVPEs能提高水稻磷素循环和再利用效率。该研究不仅能帮助了解液泡磷平衡的机制，还能帮助我们解析老叶中磷素向新叶转移和再利用的机制，为遗传改良提高作物的磷素利用效率提供理论依据。.