功能未知锌指蛋白ZHE1调控拟南芥光形态建成的分子机制研究

Plant photoreceptors sense the light in the natural surroundings and mediate the cellular light signaling transductions via interacting with different signaling proteins, thus to be profoundly implicated in plant photomorphogenesis. However, the molecular mechanisms underlying plant photomorphogenesis and its regulation are not fully understood. We previously constructed a transgenic plant population in which ~2,000 transcription factors are individually expressed. With this population, we conducted a large-scale phenotypic screen to isolate those which showed abnormal hypocotyl elongation under blue light. In this screen, an unknown zinc finger transcription factor was isolated, which was named as ZHE1 (Zinc finger-controlled Hypocotyl Elongation). Overexpression of ZHE1 in plants promote hypocotyl elongation under light, on the contrary, zhe1 mutants showed a reduced-hypocotyl length. The above data suggests that ZHE1 acts as an unknown signaling protein which plays important roles in plant photomorphogenesis. We also investigated the composition of ZHE1 complex in plants by AP-MS. ZHE1 associates with two positive regulators in photomorphogenesis, FRS7 and FRS12. Yeast-two-hybrid and co-immunoprecipitation assay in human cells also confirmed the physical interactions of ZHE1 and FRS7/12. We also found that ZHE1 locates in the cytosol. Based on these data, we speculate that ZHE1 might negatively regulate photomorphogenesis through direct suppression of FRS7/12’s activity. In this grant, we proposed to dissect the molecular functions of ZHE1 in Arabidopsis photomorphogenesis.

光受体介导植物对环境中光信号的感知并通过与信号蛋白互作将光信号在细胞内进行传递，以此调控植物的光形态建成。然而光形态建成调控的分子机制目前并不完全清楚。本实验室前期通过筛选拟南芥转录因子过表达植株群体，分离到一个功能未知的C3H类锌指蛋白基因，并将其命名为ZHE1。ZHE1过量表达在光下促进下胚轴伸长，而其突变体则与之相反，表明ZHE1是一个在光形态建成中发挥重要功能的未知光信号蛋白。通过质谱鉴定ZHE1复合体发现，在植物体内ZHE1与光形态建成正调控因子FRS7和FRS12能够在光下形成复合体。酵母双杂交与人类细胞免疫共沉淀实验也证实ZHE1与FRS7/12能够发生物理互作。此外，ZHE1蛋白定位于细胞质。基于以上结果，我们推测ZHE1可能通过直接影响FRS7和FRS12的活性而负调控拟南芥光形态建成过程，因此本研究项目拟对ZHE1参与拟南芥光形态建成调控的分子机制进行详细研究。

光形态建成是植物依赖于光而进行的细胞分化与器官形成的重要生理发育过程。从已有报道来看，植物光形态建成的分子调控网络尚不完善。通过本项目研究我们筛选到一个锌指蛋白基因ZHE1能够参与调节拟南芥在光条件下下胚轴的伸长，是一个在光形态建成中发挥重要功能的光信号蛋白。通过分子生物学，生物化学及遗传学等多种实验手段，我们提出一个新的光形态建成调控网络—光照和黑暗条件下，ZHE1均能够在细胞质中与光受体phyA发生相互作用，将phyA滞留在细胞质中，抑制其入核与下游互作蛋白结合，进而负向地调控拟南芥光形态建成的过程。ZHE1的生理生化功能尚未见报道，我们首次发现该基因在调节植物光形态建成中发挥重要作用，本研究通过深入解析ZHE1的分子功能为植物光形态建成网络提供了全新的调节机制，深化了我们对植物光形态建成分子机制的理解。

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