Dr. Kasper van Gelderen, University of Heidelberg

Phytochrome B is a crucial sensor of red and far-red light in plants, which controls plant development and environmental responses to light and temperature. In the nucleus, phyB forms phase-separated condensates, also known as photobodies, consisting of various transcriptional regulators and transcription factors. phyB photobodies can form or disperse depending on the amount of light, the quality of light, or ambient temperature. However, the biological significance of photobody formation remains unclear. Here, we hypothesize that the formation of phyB photobodies and the associated sequestration of signaling molecules enable the creation of cell-type-specific memory regarding light conditions and help smooth out the light signaling response under changing conditions. Using a combination of live and fixed seedling imaging of photobodies, along with single-nucleus transcriptomics and proximity labeling, we shed new light on the formation, composition, and function of phytochrome B photobodies.