Phytochrome independent PIF degradation: Circadian clock into the picture !

Photomorphogenesis is a crucial process for light-mediated plant growth and development. One of the important photoreceptors i.e., phytochrome B (PhyB) is responsible for the turnover of phytochrome interacting factors (PIFs). PIFs (PIF1, PIF3, PIF4, and PIF5) are transcription factors that control gene expression relevant to photomorphogenesis. Studies have highlighted the role of active PhyB in the degradation of PIFs during the day however, the regulation of PIFs by the circadian clock was unresolved. This regulation is particularly important when PhyB activity is compromised. A recent study by Liu et al. has dissected the regulation of PIFs by a circadian clock gene; clock-regulated F-box with a long hypocotyl 1 (CFH1) which is an F-box protein that degrades PIFs via the 26S proteasomal pathway. Future studies will hopefully uncover other genes involved in this newly discovered mechanism of PIF regulation.