State Key Laboratory of Plant Physiology and Biochemistry, College of Life Science, Zhejiang University, Hangzhou 310058, China.
Plant J. 2010 May;62(3):508-17. doi: 10.1111/j.1365-313X.2010.04170.x. Epub 2010 Feb 9.
Phosphate (Pi) homeostasis in plants is required for plant growth and development, and is achieved by the coordination of Pi acquisition, translocation from roots to shoots, and remobilization within plants. Previous reports have demonstrated that over-expression of OsPHR2 (the homolog of AtPHR1) and knockdown of OsSPX1 result in accumulation of excessive shoot Pi in rice. Here we report that OsPHR2 positively regulates the low-affinity Pi transporter gene OsPT2 by physical interaction and upstream regulation of OsPHO2 in roots. OsPT2 is responsible for most of the OsPHR2-mediated accumulation of excess shoot Pi. OsSPX1 suppresses the regulation on expression of OsPT2 by OsPHR2 and the accumulation of excess shoot Pi, but it does not suppress induction of OsPT2 or the accumulation of excessive shoot Pi in the Ospho2 mutant. Our data also show that OsSPX1 is a negative regulator of OsPHR2 and is involved in the feedback of Pi-signaling network in roots that is defined by OsPHR2 and OsPHO2. This finding provides new insight into the regulatory mechanism of Pi uptake, translocation, allocation and homeostasis in plants.
植物中的磷酸盐（Pi）稳态对于植物的生长和发育至关重要，这是通过 Pi 的获取、从根部向地上部的转运以及植物内的再动员的协调来实现的。先前的报告表明，过表达 OsPHR2（AtPHR1 的同源物）和敲低 OsSPX1 导致水稻中过量地上部 Pi 的积累。在这里，我们报告说 OsPHR2 通过物理相互作用和根系中 OsPHO2 的上游调节来正向调节低亲和力 Pi 转运体基因 OsPT2。OsPT2 负责 OsPHR2 介导的大部分过量地上部 Pi 的积累。OsSPX1 抑制 OsPHR2 对 OsPT2 表达的调控和过量地上部 Pi 的积累，但不抑制 OsPT2 的诱导或 Ospho2 突变体中过量地上部 Pi 的积累。我们的数据还表明，OsSPX1 是 OsPHR2 的负调节剂，参与由 OsPHR2 和 OsPHO2 定义的根系中 Pi 信号网络的反馈。这一发现为植物中 Pi 摄取、转运、分配和稳态的调节机制提供了新的见解。
