Phytochrome B inhibits the activity of phytochrome-interacting factor 7 involving phase separation

• Published in: Cell reports (Cambridge) 2023-12, Vol.42 (12), p.113562-113562, Article 113562
• Main Authors: Xie, Yu, Liu, Wenbo, Liang, Wenjing, Ling, Xiaobin, Ma, Jinbiao, Yang, Chuanwei, Li, Lin
• Format: Article
• Language: English
• Subjects: Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; CP: Molecular biology; CP: Plants; DNA-binding activity; DNA-Binding Proteins - metabolism; Factor VII - genetics; Factor VII - metabolism; Gene Expression Regulation, Plant; Light; Phase Separation; phyB; Phytochrome - metabolism; Phytochrome B - genetics; Phytochrome B - metabolism; PIF7
• ISSN: 2211-1247; 2211-1247
• DOI: 10.1016/j.celrep.2023.113562

Shade-intolerant plants sense changes in the light environment and trigger shade-avoidance syndrome in the presence of neighboring vegetation. Phytochrome-interacting factor 7 (PIF7) is an essential regulator that integrates shade signals into plant transcriptional networks. While the regulation of PIF7 under shade conditions has been well studied, the mechanism that represses PIF7 activity under white light remains ambiguous. Here, we report that PIF7 forms nuclear puncta containing phase-separated liquid-like condensates. Phytochrome B (phyB) then binds to dephosphorylated PIF7 and promotes its condensed phase of PIF7 under white light. The phyB-PIF7 condensate subsequently inhibits the DNA-binding activity of PIF7. However, shade inactivation of phyB causes the dissociation of phyB-PIF7 condensates and allows unbound PIF7 to promote the transcription of shade-induced genes. This reversible transcriptional condensation via phase separation provides sessile organisms with the flexibility of gene control to adapt to their surrounding environment. [Display omitted] •PIF7 condensates exhibit LLPS properties in vitro•PIF7 forms phase-separated liquid-like condensate in vivo•phyB-PIF7 condensates suppress the DNA-binding ability of PIF7 under white light PIF7 is a central regulator under shade, yet the mechanism that represses PIF7 activity under white light remains ambiguous. Xie et al. show that phase-separated nuclear PIF7-phyB condensates repress the DNA-binding activity of PIF7 under white light.