Phytochrome interacting factor 3

we show that light-controlled expression of the GERANYLGERANYL DIPHOSPHATE REDUCTASE (SlGGDR) gene ... is mediated by PHYTOCHROME-INTERACTING FACTOR 3 (SlPIF3)

In the absence of light, SlPIF3 physically interacts with the promoter of SlGGDR, down-regulating its expression.

light activation of phytochromes prevents the interaction between SlPIF3 and the SlGGDR promoter, leading to transcriptional derepression and higher availability of the PDP precursor for tocopherol biosynthesis

Our results show that ripening under light conditions increases tocopherol fruit content in a phytochrome-dependent manner by the transcriptional regulation of biosynthetic genes.

We demonstrate that accumulation of PIF3 in the nucleus in dark requires constitutive photomorphogenesis 1 (COP1)

Thus, we propose that PIF3 acts transiently, and its major function is to mediate phytochrome-induced signaling during the developmental switch from skotomorphogenesis to photomorphogenesis and/or dark to light transitions.

and it is not affected by COP1

Rapid light-induced degradation of PIF3 indicates that interaction of PIF3 with these phytochrome species is transient.

red (R) and far-red light (FR) induce rapid degradation of the PIF3 protein

This process is controlled by the concerted action of the R/FR absorbing phyA, phyB, and phyD photoreceptors

the poc1 mutant, a postulated PIF3 overexpressor that displays hypersensitivity to R but not to FR, lacks detectable amounts of the PIF3 protein

Here, we show that controlled degradation of the transcription factor PIF3 is a major regulatory step in light signaling.