Journal Article

Functional Characterization of Phytochrome Interacting Factor 3 for the <i>Arabidopsis thaliana</i> Circadian Clockwork

András Viczián, Stefan Kircher, Erzsébet Fejes, Andrew J. Millar, Eberhard Schäfer, László Kozma-Bognár and Ferenc Nagy

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 46, issue 10, pages 1591-1602
Published in print October 2005 | ISSN: 0032-0781
Published online October 2005 | e-ISSN: 1471-9053 | DOI:
Functional Characterization of Phytochrome Interacting Factor 3 for the Arabidopsis thaliana Circadian Clockwork

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry


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Light, in a quality- and quantity-dependent fashion, induces nuclear import of the plant photoreceptors phytochromes and promotes interaction of these receptors with transcription factors including PHYTOCHROME INTERACTING FACTOR 3 (PIF3). PIF3 was shown to form in vitro a ternary complex with the G-box element of the promoters of LATE ELONGATED HYPOCOTYL (LHY) and CIRCADIAN CLOCK ASSOCIATED 1 (CCA1) and the Pfr conformer of phytochromes. CCA1 and LHY together with TIMING OF CAB EXPRESSION 1 (TOC1) constitute a transcriptional feed-back loop that is essential for a functional circadian clock in Arabidopsis. These findings led to the hypothesis that the PIF3-containing ternary complex regulates transcription of light-responsive genes and is involved in phototransduction to the central circadian clockwork. Here we report that (i) overexpression or lack of biologically functional PIF3 does not affect period length of rhythmic gene expression or red-light-induced resetting of the circadian clock and (ii) the transcription of PIF3 displays a low-amplitude circadian rhythm. We demonstrated previously that irradiation of etiolated seedlings induces rapid, phytochrome-controlled degradation of PIF3. Here we show that nuclear-localized PIF3 accumulates to relatively high levels by the end of the light phase in seedlings grown under diurnal conditions. Taken together, we show that (i) PIF3 does not play a significant role in controlling light input to and function of the circadian clockwork and (ii) a yet unknown mechanism limits phytochrome-induced degradation of PIF3 at the end of the day under diurnal conditions.

Keywords: Circadian clock; Light; Phototransduction; Phytochrome; Protein degradation

Journal Article.  8185 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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