Department of Botany and Plant Sciences, Institute for Integrative Genome Biology, University of California, Riverside, CA, 92521, USA.
Plant Molecular Biology and Biotechnology Research Center, Gyeongsang National University, Jinju, 52828, Republic of Korea.
Nat Commun. 2024 Apr 29;15(1):3620. doi: 10.1038/s41467-024-47789-1.
Photobodies (PBs) are membraneless subnuclear organelles that self-assemble via concentration-dependent liquid-liquid phase separation (LLPS) of the plant photoreceptor and thermosensor phytochrome B (PHYB). The current PHYB LLPS model posits that PHYB phase separates randomly in the nucleoplasm regardless of the cellular or nuclear context. Here, we established a robust Oligopaints method in Arabidopsis to determine the positioning of individual PBs. We show surprisingly that even in PHYB overexpression lines - where PHYB condensation would be more likely to occur randomly - PBs positioned at twelve distinct subnuclear locations distinguishable by chromocenter and nucleolus landmarks, suggesting that PHYB condensation occurs nonrandomly at preferred seeding sites. Intriguingly, warm temperatures reduce PB number by inducing the disappearance of specific thermo-sensitive PBs, demonstrating that individual PBs possess different thermosensitivities. These results reveal a nonrandom PB nucleation model, which provides the framework for the biogenesis of spatially distinct individual PBs with diverse environmental sensitivities within a single plant nucleus.
光体（PBs）是无膜亚核细胞器，通过植物光受体和热传感器phytochrome B（PHYB）的浓度依赖的液-液相分离（LLPS）自组装。目前的 PHYB LLPS 模型假设 PHYB 随机在核质中相分离，而不考虑细胞或核环境。在这里，我们在拟南芥中建立了一种稳健的寡聚探针方法来确定单个 PB 的定位。我们惊讶地发现，即使在 PHYB 过表达系中 - 其中 PHYB 凝聚更有可能随机发生 - PB 定位在十二个不同的亚核位置，可通过着丝粒和核仁标记物区分，这表明 PHYB 凝聚在优先的成核位点发生非随机。有趣的是，温暖的温度通过诱导特定热敏感 PB 的消失来减少 PB 的数量，表明单个 PB 具有不同的热敏感性。这些结果揭示了一个非随机的 PB 成核模型，为在单个植物核内具有不同环境敏感性的空间不同的单个 PB 的生物发生提供了框架。
