Kim Ruth Jean Ae, Fan De, He Jiangman, Kim Keunhwa, Du Juan, Chen Meng
Department of Botany and Plant Sciences, Institute for Integrative Genome Biology, University of California, Riverside, CA 92521, USA.
These authors contributed equally.
bioRxiv. 2024 Jan 5:2023.11.12.566724. doi: 10.1101/2023.11.12.566724.
Photoactivation of the plant photoreceptor and thermosensor phytochrome B (PHYB) triggers its condensation into subnuclear photobodies (PBs). However, the function of PBs remains frustratingly elusive. Here, we found that PHYB recruits PHYTOCHROME-INTERACTING FACTOR5 (PIF5) to PBs. Surprisingly, PHYB exerts opposing roles in degrading and stabilizing PIF5. Perturbing PB size by overproducing PHYB provoked a biphasic PIF5 response: while a moderate increase in PHYB enhanced PIF5 degradation, further elevating the PHYB level stabilized PIF5 by retaining more of it in enlarged PBs. These results reveal a PB-mediated light and temperature sensing mechanism, in which PHYB condensation confers the co-occurrence and competition of two antagonistic phase-separated PHYB signaling actions-PIF5 stabilization in PBs and PIF5 degradation in the surrounding nucleoplasm-thereby enabling an environmentally-sensitive counterbalancing mechanism to titrate nucleoplasmic PIF5 and its transcriptional output. This PB-enabled signaling mechanism provides a framework for regulating a plethora of PHYB-interacting signaling molecules in diverse plant environmental responses.
植物光感受器和热传感器光敏色素B（PHYB）的光激活触发其凝聚成核内光小体（PBs）。然而，PBs的功能仍然令人沮丧地难以捉摸。在这里，我们发现PHYB将光敏色素相互作用因子5（PIF5）招募到PBs中。令人惊讶的是，PHYB在降解和稳定PIF5方面发挥着相反的作用。通过过量表达PHYB来扰动PB大小引发了PIF5的双相反应：虽然适度增加PHYB会增强PIF5的降解，但进一步提高PHYB水平会通过将更多的PIF5保留在扩大的PBs中而使其稳定。这些结果揭示了一种PB介导的光和温度传感机制，其中PHYB凝聚赋予了两种拮抗的相分离PHYB信号传导作用——PBs中PIF5的稳定和周围核质中PIF5的降解——的同时发生和竞争，从而实现一种对环境敏感的平衡机制来滴定核质中的PIF5及其转录输出。这种由PB启用的信号传导机制为在不同植物环境反应中调节大量与PHYB相互作用的信号分子提供了一个框架。
