Nozue, Kazunari , Harmer, Stacey, L , Covington, Michael, F , Duek, Paula , Lorrain, Séverine , Fankhauser, Christian , Maloof, Julin, N .
The circadian clock and light signaling converge on PIF4 and PIF5 to control rhythmic hypocotyl growth.
Most organisms use circadian oscillators to anticipate daily environmental changes, but little is known about how circadian systems interact with normal diurnal signals (1). We have shown that the growth phase of Arabidopsis seedlings in diurnal light conditions is shifted 8-12 hours relative to plants in continuous light. Previously we found that the clock regulates transcript levels of two bHLH genes, PIF4 and PIF5, while light regulates their activity. Here we show that light regulates their protein abundance and that PIF4 and PIF5 function downstream of the clock. These genes work as positive growth regulators; the coincidence of high transcript levels (by the clock) and protein accumulation (in the dark) allow them to promote plant growth at the end of the night. Thus these two genes integrate clock and light signaling and their coordinate regulation explains the observed diurnal growth rhythms. We are currently examining if our external coincidence model applies to the growth patterns of various photoreceptor mutants.
This light and clock interaction may serve as a paradigm for understanding how endogenous and environmental signals cooperate to control other processes.
(1) Nozue and Maloof (2006) Plant Cell and Environment 26:396-408
(2) Nozue et al (2007) Nature, in press
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1 - University of California, Davis, Section of Plant Biology, College of Biological Sciences, One Shields Avenue, Davis, CA, 95616, USA
2 - University of Lausanne, Switzerland, Center for Integrative Genomics
Presentation Type: ASPB Minisymposium
Location: Continental B/Hilton
Date: Sunday, July 8th, 2007
Time: 5:00 PM