Abstract：
Plants maintain iron (Fe) homeostasis under varying environmental conditions by balancing processes such as Fe uptake, transport and storage. In Arabidopsis, POPEYE (PYE), a basic helix-loop-helix transcription factor (TF), has been shown to play a crucial role in regulating this balance. In recent years, the mechanisms regulating Fe uptake have been well established but the upstream transcriptional regulators of Fe transport and storage are still poorly understood. In this study, we report that ELONGATED HYPOCOTYL5 (HY5), a basic leucine zipper (bZIP) TF which has recently been shown to play a crucial role in Fe homeostasis, interacts with PYE. Molecular, genetic and biochemical approaches revealed that PYE and HY5 have overlapping as well as some distinct roles in the regulation of Fe deficiency response. We found that HY5 and PYE both act as a repressor of Fe transport genes such as YSL3, FRD3, NPF5.9, YSL2, NAS4 and OPT3. HY5 was found to directly bind on the promoter of these genes and regulate intercellular Fe transport. Further analysis revealed that HY5 and PYE directly interact at the same region on PYE and NAS4 promoter. Overall, this study revealed that HY5 regulates Fe homeostasis by physically interacting with PYE as well as independently.
摘要：
植物通过平衡铁吸收等过程，在不同的环境条件下维持铁（Fe）稳态。运输和储存。在拟南芥中,POPEYE(PYE),一个基本的螺旋-环-螺旋转录因子（TF），已被证明在调节这种平衡方面发挥着至关重要的作用。近年来,调节Fe摄取的机制已经很好地建立，但是对Fe运输和储存的上游转录调节因子仍然知之甚少。在这项研究中,我们报告了延长的下染色体5(HY5)，一种碱性亮氨酸拉链（bZIP）TF，最近被证明在铁稳态中起关键作用，与PYE互动。分子,遗传和生化方法表明，PYE和HY5在铁缺乏反应的调节中具有重叠和一些不同的作用。我们发现HY5和PYE都是Fe转运基因如YSL3、FRD3、NPF5.9、YSL2、NAS4和OPT3的抑制因子。发现HY5直接结合在这些基因的启动子上并调节细胞间Fe运输。进一步分析显示HY5和PYE在PYE和NAS4启动子上的同一区域直接相互作用。总的来说,这项研究表明，HY5通过与PYE物理相互作用以及独立地调节Fe稳态。
