PIF3, a phytochrome-interacting factor necessary for normal photoinduced signal transduction, is a novel basic helix-loop-helix protein.
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.
Mesh Terms:
Arabidopsis, Arabidopsis Proteins, Basic Helix-Loop-Helix Transcription Factors, Cell Nucleus, DNA, Plant, Helix-Loop-Helix Motifs, Molecular Sequence Data, Oligonucleotides, Antisense, Photoreceptor Cells, Phytochrome, Phytochrome A, Phytochrome B, Plants, Genetically Modified, Sequence Homology, Amino Acid, Signal Transduction, Transcription Factors, Transfection, Yeasts
Arabidopsis, Arabidopsis Proteins, Basic Helix-Loop-Helix Transcription Factors, Cell Nucleus, DNA, Plant, Helix-Loop-Helix Motifs, Molecular Sequence Data, Oligonucleotides, Antisense, Photoreceptor Cells, Phytochrome, Phytochrome A, Phytochrome B, Plants, Genetically Modified, Sequence Homology, Amino Acid, Signal Transduction, Transcription Factors, Transfection, Yeasts
Cell
Date: Nov. 25, 1998
PubMed ID: 9845368
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