Department of Botany and Plant Sciences, Institute for Integrative Genome Biology, University of California, Riverside, CA, 92521, USA.
Department of Molecular Biology, Max Planck Institute for Developmental Biology, 72076, Tübingen, Germany.
Nat Commun. 2019 Jun 14;10(1):2629. doi: 10.1038/s41467-019-10518-0.
Light initiates chloroplast biogenesis by activating photosynthesis-associated genes encoded by not only the nuclear but also the plastidial genome, but how photoreceptors control plastidial gene expression remains enigmatic. Here we show that the photoactivation of phytochromes triggers the expression of photosynthesis-associated plastid-encoded genes (PhAPGs) by stimulating the assembly of the bacterial-type plastidial RNA polymerase (PEP) into a 1000-kDa complex. Using forward genetic approaches, we identified REGULATOR OF CHLOROPLAST BIOGENESIS (RCB) as a dual-targeted nuclear/plastidial phytochrome signaling component required for PEP assembly. Surprisingly, RCB controls PhAPG expression primarily from the nucleus by interacting with phytochromes and promoting their localization to photobodies for the degradation of the transcriptional regulators PIF1 and PIF3. RCB-dependent PIF degradation in the nucleus signals the plastids for PEP assembly and PhAPG expression. Thus, our findings reveal the framework of a nucleus-to-plastid anterograde signaling pathway by which phytochrome signaling in the nucleus controls plastidial transcription.
光通过激活不仅由核编码，而且由质体基因组编码的光合作用相关基因来启动叶绿体生物发生，但光受体如何控制质体基因表达仍然是个谜。在这里，我们发现，光敏色素的光激活通过刺激细菌型质体 RNA 聚合酶（PEP）组装成 1000 kDa 的复合物，触发与光合作用相关的质体编码基因（PhAPGs）的表达。使用正向遗传学方法，我们鉴定了调控叶绿体生物发生（RCB）作为一种双靶向核/质体光敏色素信号成分，是 PEP 组装所必需的。令人惊讶的是，RCB 通过与光敏色素相互作用并促进其定位到光体中以降解转录调节剂 PIF1 和 PIF3，主要从核中控制 PhAPG 的表达。核中 RCB 依赖性 PIF 降解为 PEP 组装和 PhAPG 表达发出质体信号。因此，我们的发现揭示了一个从核到质体的顺行信号通路的框架，通过该通路，核中的光敏色素信号控制质体转录。
