Photo-dependent membrane-less organelles formed from plant phyB and PIF6 proteins in mammalian cells

Plant photobodies are the membrane-less organelles (MLOs) that can be generated by protein-protein interactions between active form of phytochrome B (phyB) and phytochrome-interacting factors (PIFs). These organelles regulate plant photomorphogenesis. In this study, we developed two chimeric proteins with fluorescent proteins, phyB fused to EGFP and PIF6 fused to mCherry, and investigated their exogenous expression in mammalian cells by confocal fluorescence microscopy. Results showed that irradiation with diffused 630-nm light induced formation and subsequent increase in sizes of the MLOs. The assembly and disassembly of the photo-inducible MLOs in the mammalian cell cytoplasm obeyed the laws inherent in the concentration-dependent phase separation of biopolymers. The sizes of MLOs formed from phyB and PIF6 in mammalian cells corresponded to the sizes of the so-called early photobodies in plant cells. These results suggested that the first step for the formation of plant photobodies might be based on the light-dependent liquid-liquid phase separation of PIFs and other proteins that can specifically interact with the active form of phyB. The developed chimeric proteins in principle can be used to control the assembly and disassembly of photo-inducible MLOs, and thereby to regulate various intracellular processes in mammalian cells. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

Plant photobodies are membrane-less organelles generated by protein interactions, regulating plant photomorphogenesis. In mammalian cells, the assembly and disassembly of photo-inducible MLOs follow concentration-dependent phase separation, suggesting a potential mechanism for control of intracellular processes. The developed chimeric proteins can be utilized to manipulate the formation and disassembly of these organelles in mammalian cells.