| Function |
Regulatory photoreceptor which exists in two forms that are reversibly interconvertible by light: the Pr form that absorbs maximally in the red region of the spectrum and the Pfr form that absorbs maximally in the far-red region. Photoconversion of Pr to Pfr induces an array of morphogenetic responses, whereas reconversion of Pfr to Pr cancels the induction of those responses. Pfr controls the expression of a number of nuclear genes including those encoding the small subunit of ribulose-bisphosphate carboxylase, chlorophyll A/B binding protein, protochlorophyllide reductase, rRNA, etc. It also controls the expression of its own gene(s) in a negative feedback fashion. Involved in the flowering time regulation. Involved in light-regulated circadian phase control that triggers stomatal aperture, stomatal conductance, and CO2 assimilation. Implicated in red light perception, and, to a lower extent, in blue light signaling. Controls thermomorphogenesis in the daytime and regulates temperature responses by associating with the promoters of key target genes in a temperature-dependent manner and subsequently repressing their expression in a PIF4-dependent manner (temperature-responsive transcriptional regulator); this process requires PTAC12/HMR/PAP5 (transcriptional activator). Thermal timer that integrates temperature information over the course of the night. Detabilizes UNE10/PIF8 in red light.
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