PIF3, a phytochrome-interacting factor necessary for normal photoinduced signal transduction, is a novel basic helix-loop-helix protein

Cell. 1998 Nov 25;95(5):657-67. doi: 10.1016/s0092-8674(00)81636-0.


The mechanism by which the phytochrome (phy) photoreceptor family transduces informational light signals to photoresponsive genes is unknown. Using a yeast two-hybrid screen, we have identified a phytochrome-interacting factor, PIF3, a basic helix-loop-helix protein containing a PAS domain. PIF3 binds to wild-type C-terminal domains of both phyA and phyB, but less strongly to signaling-defective, missense mutant-containing domains. Expression of sense or antisense PIF3 sequences in transgenic Arabidopsis perturbs photoresponsiveness in a manner indicating that PIF3 functions in both phyA and phyB signaling pathways in vivo. PIF3 localized to the nucleus in transient transfection experiments, indicating a potential role in controlling gene expression. Together, the data suggest that phytochrome signaling to photoregulated genes includes a direct pathway involving physical interaction between the photoreceptor and a transcriptional regulator.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Arabidopsis / chemistry
  • Arabidopsis Proteins*
  • Basic Helix-Loop-Helix Transcription Factors
  • Cell Nucleus / metabolism
  • DNA, Plant / chemistry
  • Helix-Loop-Helix Motifs / physiology*
  • Molecular Sequence Data
  • Oligonucleotides, Antisense / metabolism
  • Photoreceptor Cells*
  • Phytochrome / chemistry
  • Phytochrome / genetics
  • Phytochrome / metabolism
  • Phytochrome / physiology*
  • Phytochrome A
  • Phytochrome B
  • Plants, Genetically Modified
  • Sequence Homology, Amino Acid
  • Signal Transduction / physiology*
  • Transcription Factors*
  • Transfection
  • Yeasts


  • Arabidopsis Proteins
  • Basic Helix-Loop-Helix Transcription Factors
  • DNA, Plant
  • Oligonucleotides, Antisense
  • PHYA protein, Arabidopsis
  • PHYB protein, Arabidopsis
  • PIF3 protein, Arabidopsis
  • Phytochrome A
  • Transcription Factors
  • Phytochrome
  • Phytochrome B

Associated data

  • GENBANK/AC003970
  • GENBANK/AF100166