PHT1翻译后磷酸化修饰调控水稻磷养分吸收的分子机制研究

Chemical fertilizer has been over applied on rice growing in China so that heavily threatening the environment. Enhancing Pi-uptake efficiency in rice has great significance for the sustainability of agriculture. Post-translation modification is the leading edge and hotspots of phosphate-uptake regulation in rice. The phosphate transporter proteins PHT1 are the key protein family for phosphate uptake and translocation. Phosphorylation and dephosphorylation of PHT1 is finely regulated for maintaining Pi homestasis in rice. The authors’ recent progress on this topic is published on Plant cell in 2015. Moreover, besides we find that phosphorylation of PHT1 is regulated by the protein kinase CK2, we rencently find protein phosphatase OsPP95 and OsPP46 may be involved in the modification of PHT1 activity. Not only direct binding is found between the phosphatase and PHT1, but also the two phosphatase regulate phosphate uptake as well. In order to further elucidate the detail of the relationship between the proteins, we apply this fund do more research on this field using modern molecular and biological technologies. It would provide more detail information for enhancing Pi- uptake efficiency in rice.

我国水稻生产过度依赖化肥投入，造成严重的环境污染。提升水稻对磷养分吸收的效率对水稻产量的可持续增加具有重要的战略意义。水稻磷养分吸收转运蛋白翻译后调控是当前国际上研究的前沿和热点。磷酸盐转运体蛋白PHT1的磷酸化和脱磷酸化对植物体内的Pi水平的动态平衡起着关键的调节作用，申请人相关最新成果发表于Plant Cell（2015）。PHT1的磷酸化水平除受CK2激酶调节外，本研究新近发现蛋白磷酸酶PP2C家族的OsPP95和OsPP46也与PHT1结合来调控水稻磷养分的吸收，推测可能参与PHT1磷酸化水平的负向调控。为进一步阐明PHT1在翻译后水平的磷酸化修饰调控机制，本研究采用前沿分子生物学和生物化学手段对相关基因的功能和作用模型进一步深入解析，为提高作物磷吸收利用效率提供理论依据。

磷素作为植物生长不可或缺的大量元素之一，它在土壤中的含量严重的影响着农作物产量。一方面上，磷矿资源有限导致许多地区土壤缺乏磷肥；另方面上，由于过度使用磷肥，导致局部地区磷养分污染。因此，研究水稻对磷养分的吸收、转运调控的分子机制对水稻产量的可持续性提升具有重要的意义。在该项目中，以细胞膜定位的PHT1家族磷酸盐转运体OsPT8为研究对象，研究其在蛋白质修饰水平上的分子调控机制。我们通过酵母双杂交系统的筛选，鉴定到一个隶属于PP2C家族的且活性依赖于Mn2+磷酸酶OsPP95。通过酵母双杂交，Co-IP，Pull-down试验以及体内体外蛋白磷酸化试验，证明OsPP95可以与PT8的C末端互作，负调控PT8第517位Ser的磷酸化，正好与CK2激酶相互拮抗调控PT8的内质网上的磷酸化状态，从而调控PT8在内质网上的输出。结合转基因等遗传材料的相关的磷生理试验，我们得出结论，PP95蛋白通过对磷酸盐转运体（PTs）的去磷酸化调控，影响PT在细胞膜上的定位，从而调控植株体内磷的动态平衡和磷再分配，这是植株适应环境磷养分变化的可逆的且精细的调控机制。