Ni M, Tepperman J M, Quail P H
Department of Plant and Microbial Biology, University of California, Berkeley 94720, USA.
Cell. 1998 Nov 25;95(5):657-67. doi: 10.1016/s0092-8674(00)81636-0.
The mechanism by which the phytochrome (phy) photoreceptor family transduces informational light signals to photoresponsive genes is unknown. Using a yeast two-hybrid screen, we have identified a phytochrome-interacting factor, PIF3, a basic helix-loop-helix protein containing a PAS domain. PIF3 binds to wild-type C-terminal domains of both phyA and phyB, but less strongly to signaling-defective, missense mutant-containing domains. Expression of sense or antisense PIF3 sequences in transgenic Arabidopsis perturbs photoresponsiveness in a manner indicating that PIF3 functions in both phyA and phyB signaling pathways in vivo. PIF3 localized to the nucleus in transient transfection experiments, indicating a potential role in controlling gene expression. Together, the data suggest that phytochrome signaling to photoregulated genes includes a direct pathway involving physical interaction between the photoreceptor and a transcriptional regulator.
光敏色素（phy）光受体家族将信息光信号转导至光响应基因的机制尚不清楚。通过酵母双杂交筛选，我们鉴定出一种与光敏色素相互作用的因子PIF3，它是一种含有PAS结构域的碱性螺旋-环-螺旋蛋白。PIF3可与phyA和phyB的野生型C末端结构域结合，但与含有信号缺陷型错义突变的结构域结合较弱。在转基因拟南芥中表达正义或反义PIF3序列会以一种表明PIF3在体内phyA和phyB信号通路中均起作用的方式扰乱光响应。在瞬时转染实验中，PIF3定位于细胞核，表明其在控制基因表达方面具有潜在作用。总之，这些数据表明，光敏色素向光调节基因的信号转导包括一条直接途径，该途径涉及光受体与转录调节因子之间的物理相互作用。
