Phytochrome Photobodies In Mammalian Cells

Photobodies play a significant role in photomorphogenesis and scotomorphogenesis in higher plants. Assemble/disassemble of these membrane-less organelles (MLOs) are induced by light photoconvertion of phytochromes and cryptochromes, which are their scaffold proteins. For example, the formation of phytochromes-based photobodies often are caused by interaction of active phytochrome B (phyB) Pfr conformers with phytochrome-interacting factors (PIFs). We showed that MLOs based on plant phyB and PIFs can arise in mammalian cells (HEK 293) and that red/far-red cell irradiation induces the increase/decrease of the size of these photobodies. It was shown that light-induced phase separation of phyB/PIF6 complexes in the mammalian cell cytoplasm obeys the laws inherent in the concentration-dependent phase separation of biopolymers. Probably, initiation the formation of photobodies may be determined by the light-dependent liquid-liquid phase separation of PIFs factors that specifically interact with the active form of phyB. It is known that the phyB heterodimerization with PIFs is crucial for the photo-dependent control of various cellular processes in the cells of almost all plants. Our data indicate that this pair of proteins can also be used to create optogenetic systems associated with the control of the characteristics of various membrane-less organelles. The work was supported by the Russian Science Foundation (RSF No 18-75-10115).