Phytochrome activates the plastid-encoded RNA polymerase for chloroplast biogenesis via nucleus-to-plastid signaling

First author: Chan Yul Yoo; Affiliations: University of California (加利福尼亚大学): Riverside, USA

Corresponding author: Meng Chen

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.

光通过激活光合相关基因的表达起始叶绿体的生物发生，这些光合相关基因有的由核基因组编码，有的由质体基因组编码，但光受体如何控制质体基因表达还不清楚。本文中，作者的研究显示光敏色素的光激活会通过刺激细菌型质体RNA聚合酶PEP组装形成一个1000kDa的复合体，从而诱导光合相关质体编码基因PhAPGs的表达。利用正向遗传学方法，作者鉴定了一个PEP组装必需的叶绿体生物发生调节器RCB作为一个核/质体双重靶向光敏色素信号组份。有趣的是，RCB通过与光敏色素的互作控制PhAPG的表达，促进其定位于光体，从而降解转录调控子PIF1和PIF3。细胞核中RCB依赖型的PIF降解示意质体用于PEP组装和PhAPG表达。因此，本文的发现揭示了一个核-质顺向信号通路，而其中核内的细胞色素信号控制着质体转录。

通讯：Meng Chen (http://www.plasticgenome.org/members-of-chen-lab/)

个人简介：爱荷华州立大学，本硕博。

研究方向：光体在光信号中的功能；控制叶绿体转录的光敏色素；植物光信号诱导的基因组空间重组。

doi: https://doi.org/10.1038/s41467-019-10518-0

Journal: Nature Communication

Published date: June 14, 2019