PHYTOCHROME-INTERACTING FACTORS PIF4 and PIF5 Are Implicated in the Regulation of Hypocotyl Elongation in Response to Blue Light inArabidopsis thaliana

In Arabidopsis thaliana, plant growth, including elongation of hypocotyl is regulated in response to light conditions through circadian clock-controlled PHYTOCHROME-INTERACTING FACTORs PIF4 and PIF5. In this study, we found that these transcription factors were responsible not only for red light signaling through the phytochromes but also for blue light signaling in the photomorphogenic control of hypocotyl elongation. It is possible that plant hormone gibberellins play an important role in blue light signaling in part through PIF4/PIF5.