Arabidopsis phyB functions as a green light photoreceptor to promote photomorphogenesis

Although green light (GL, 500–600 nm) occupies half the visible light spectrum and regulates a series of plant developmental processes, the mechanism by which GL regulates seedling morphogenesis is enigmatic. Here, we reported that pure GL (500–600 nm, λ max , 527 nm) promoted the cotyledon development of Arabidopsis seedlings through phytochrome B (phyB). Genetic analysis indicated that phyB was involved in cotyledon development under continuous GL. Compared with red light (RL), GL induced phyB translocation from the cytoplasm to the nucleus and speckle-like photobody formation with a slower rate, which was reversed by far red light. Further transcriptomic data demonstrated that phyB participated in GL-responsive transcriptional networks in concert with four PHYTOCHROME-INTERACTING FACTORS (PIFs, PIF1, PIF3, PIF4, and PIF5). As expected, protein levels of the PIFs were decreased by GL. Similar to RL, GL induced the rapid degradation of PIF3 in a phy-dependent manner. Our results suggest that pure GL (527 nm) leads to the migration of phyB into the nucleus to trigger photomorphogenesis by possibly promoting the degradation of PIFs.