铁是一种植物必需的矿质元素。FIT作为拟南芥铁稳态的一个核心调控因子，在转录水平和转录后水平受到缺铁调控。FIT蛋白受到泛素介导的26S蛋白酶体降解调控，但背后机制仍然不清楚。在前期研究中，我们筛选到两个FIT的互作蛋白FIP1（FIT Interaction Protein 1）和FIP2，它们都含一种典型的E3泛素连接酶功能结构域RING。初步研究结果表明FIP1/2与FIT在细胞核内互作并促进了后者的的降解。而且在缺铁条件下fip双突变体展示出与fit突变体相反的表型。这些结果暗示FIP蛋白可能通过泛素化途径降解FIT。本项目将采用分子生物学、遗传学及生物化学的方法，系统分析拟南芥FIP1/2泛素化调控FIT蛋白的分子机制。本研究对于深入理解FIPs调控植物铁稳态信号通路具有重要的意义。

Iron is an essential micronutrient for plants. FIT （Fer-Like Iron-Deficiency Induced Transcription Factor）as a core regulator of iron homeostasis is regulated by iron deficiency at transcriptional regulation and post-transcriptional level in Arabidopsis. FIT protein is degraded by ubiquitin-mediated proteolysis, but the underpinning mechanism remains unclear. Our previous work screened two interaction partner of FIT, FIP1 （FIT Interaction Protein 1） and FIP2 containing a canonical RING finger domain type ligase. Preliminary research results indicate that FIP1/2 interacted with FIT in the nucleus and promoted the degradation of FIT. Furthermore, the fip double mutant exhibited the opposite phenotype of the fit mutant under iron deficiency. These results suggest that FIP protein may modulate degradation of FIT through the ubiquitination pathway.We will undertake molecular, genetic and biochemical approaches in this project to further elucidate molecular mechanisms which FIP1/2 modulate the ubiquitination of FIT. Our study will contribute to the understanding of FIPs-mediated iron homeostasis signaling pathway in plants.