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Gene Review

PIF3  -  transcription factor PIF3

Arabidopsis thaliana

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Disease relevance of PIF3

  • In addition, we provide evidence that the poc1 mutant, a postulated PIF3 overexpressor that displays hypersensitivity to R but not to FR, lacks detectable amounts of the PIF3 protein [1].

High impact information on PIF3

  • PIF3, a phytochrome-interacting factor necessary for normal photoinduced signal transduction, is a novel basic helix-loop-helix protein [2].
  • Using a yeast two-hybrid screen, we have identified a phytochrome-interacting factor, PIF3, a basic helix-loop-helix protein containing a PAS domain [2].
  • PIF3 localized to the nucleus in transient transfection experiments, indicating a potential role in controlling gene expression [2].
  • Here we show that full-length photoactive phytochrome B binds PIF3 in vitro only upon light-induced conversion to its active form, and that photoconversion back to its inactive form causes dissociation from PIF3 [3].
  • Thus, HFR1 may function to modulate phyA signaling via heterodimerization with PIF3 [4].

Biological context of PIF3

  • The mutant phenotype seems to result from insertion-induced overexpression of this gene in red-light-grown seedlings, consistent with PIF3 functioning as a positively acting signaling intermediate [5].
  • Here, we show that the basic helix-loop-helix transcription factor PIF3 binds specifically to a G-box DNA-sequence motif present in various light-regulated gene promoters, and that phytochrome B binds reversibly to G-box-bound PIF3 specifically upon light-triggered conversion of the photoreceptor to its biologically active conformer [6].
  • Based on evidence that the bHLH protein PIF3 is a direct phytochrome reaction partner in the photoreceptor's signaling network, we have undertaken a comprehensive computational analysis of the Arabidopsis genome sequence databases to define the scope and features of the bHLH family [7].
  • Conversely, deletion mapping and point mutation analysis of PIF3 for determinants involved in recognition of phyB indicates that the PAS domain of PIF3 is a major contributor to this interaction, but that a second determinant in the C-terminal domain is also necessary [8].
  • Upon absorption of red light, phytochrome translocates from the cytoplasm to the nucleus, and regulates gene expression through interaction with transcription factors such as PIF3 (refs 5-7) [9].

Anatomical context of PIF3


Regulatory relationships of PIF3

  • These results suggest that PIF3 may play an important role in the control of flowering through clock-independent regulation of CO and FT gene expression in Arabidopsis [11].

Other interactions of PIF3


  1. Constitutive photomorphogenesis 1 and multiple photoreceptors control degradation of phytochrome interacting factor 3, a transcription factor required for light signaling in Arabidopsis. Bauer, D., Viczián, A., Kircher, S., Nobis, T., Nitschke, R., Kunkel, T., Panigrahi, K.C., Adám, E., Fejes, E., Schäfer, E., Nagy, F. Plant Cell (2004) [Pubmed]
  2. PIF3, a phytochrome-interacting factor necessary for normal photoinduced signal transduction, is a novel basic helix-loop-helix protein. Ni, M., Tepperman, J.M., Quail, P.H. Cell (1998) [Pubmed]
  3. Binding of phytochrome B to its nuclear signalling partner PIF3 is reversibly induced by light. Ni, M., Tepperman, J.M., Quail, P.H. Nature (1999) [Pubmed]
  4. HFR1 encodes an atypical bHLH protein that acts in phytochrome A signal transduction. Fairchild, C.D., Schumaker, M.A., Quail, P.H. Genes Dev. (2000) [Pubmed]
  5. poc1: an Arabidopsis mutant perturbed in phytochrome signaling because of a T DNA insertion in the promoter of PIF3, a gene encoding a phytochrome-interacting bHLH protein. Halliday, K.J., Hudson, M., Ni, M., Qin, M., Quail, P.H. Proc. Natl. Acad. Sci. U.S.A. (1999) [Pubmed]
  6. Direct targeting of light signals to a promoter element-bound transcription factor. Martínez-García, J.F., Huq, E., Quail, P.H. Science (2000) [Pubmed]
  7. The Arabidopsis basic/helix-loop-helix transcription factor family. Toledo-Ortiz, G., Huq, E., Quail, P.H. Plant Cell (2003) [Pubmed]
  8. Phytochrome B binds with greater apparent affinity than phytochrome A to the basic helix-loop-helix factor PIF3 in a reaction requiring the PAS domain of PIF3. Zhu, Y., Tepperman, J.M., Fairchild, C.D., Quail, P.H. Proc. Natl. Acad. Sci. U.S.A. (2000) [Pubmed]
  9. Dimers of the N-terminal domain of phytochrome B are functional in the nucleus. Matsushita, T., Mochizuki, N., Nagatani, A. Nature (2003) [Pubmed]
  10. Microarray analysis of brassinosteroid-regulated genes in Arabidopsis. Goda, H., Shimada, Y., Asami, T., Fujioka, S., Yoshida, S. Plant Physiol. (2002) [Pubmed]
  11. Antisense suppression of the Arabidopsis PIF3 gene does not affect circadian rhythms but causes early flowering and increases FT expression. Oda, A., Fujiwara, S., Kamada, H., Coupland, G., Mizoguchi, T. FEBS Lett. (2004) [Pubmed]
  12. Phytochrome phosphorylation modulates light signaling by influencing the protein-protein interaction. Kim, J.I., Shen, Y., Han, Y.J., Park, J.E., Kirchenbauer, D., Soh, M.S., Nagy, F., Schäfer, E., Song, P.S. Plant Cell (2004) [Pubmed]
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