PHO2编码E2泛素结合酶UBC24，是PHR1-miR399/IPS1-PHO2磷信号通路中调控磷稳态的重要负调控因子。我们近期研究发现拟南芥与水稻 PHO2蛋白在功能上存在重要的差异。酵母双杂交筛选缺磷水稻cDNA文库，获得了与OsPHO2互作的硫氧还蛋白TrxA和TrxB，并明确这种互作在拟南芥中不存在。本研究拟利用定点突变结合酵母双杂等蛋白互作技术，明确OsPHO2蛋白中与硫氧还蛋白互作的关键半胱氨基酸位点；分析互作蛋白TrxA/B的超表达和抑制表达材料，阐明TrxA/B参与调控OsPHO2的氧化还原状态的机制及其功能；培育在水稻pho2中表达野生型OsPHO2和互作位点突变OsPHO2-M的转基因材料，并比较其生理特性和植株磷稳态变化，阐明OsPHO2蛋白氧化态和还原态的调控机制及其功能。本研究将为完善水稻磷信号网络、指导磷高效分子育种提供重要依据。

PHO2, encoding an ubiquitin E2 conjugase (UBC24), is an important negative regulator of the PHR1-miR399/IPS1-PHO2 signal pathway in plant phosphate homeostasis. Our unpublished data showed that there is a significant function difference between rice and arabidopsis PHO2. Yeast two hybridization screening of the rice phosphate-deficient cDNA library identified two thioredoxins, OsTrxA and OsTrxB, interacting with OsPHO2. The interaction is a rice-specific. In other words, it does not existing in Arabidopsis. In this study, we will use site-mutagenesis to construct the mutant versions of OsPHO2s, in which the putative interaction sites, cysteins, in the OsPHO2 amino acid sequence were mutated into alanine or serine to abolish the reduction mediated by the thioredoxins OsTrxA and OsTrxB. Transgenic rice plants with enhanced or reduced expression levels of TrxA and B will be created through overexpression, RNA interference, and CRISPR technology. The physiological performance and phosphate homeostasis of these transgenic plants will be evaluated to unravel the mechanism and function that TrxA/B regulate the oxidative/reductive status of OsPHO2. In addition, the wildtype and mutant forms of OsPHO2 will be expressed into the ospho2 mutant rice to see the roles of the oxidative/reductive status of OsPHO2 on phosphate homeostasis. The study will elucidate a new molecular mechanism to complete the rice phosphate signaling network. The new knowledge is potentially useful for engineering of rice plants with improved phosphorus use efficiency.