Multiple phytohormones influence distinct parameters of the plant circadian clock

Shigeru Hanano, Malgorzata A Domagalska, Ferenc Nagy, Seth J Davis

Research output: Contribution to journalA2: International peer reviewed article (not A1-type)peer-review


Circadian systems coordinate endogenous events with external signals. In mammals, hormone-clock feedbacks are a well-known integration system. Here, we investigated phytohormone effects on plant-circadian rhythms via the promoter:luciferase system. We report that many hormones control specific features of the plant-circadian system, and do so in distinct ways. In particular, cytokinins delay circadian phase, auxins regulate circadian amplitude and clock precision, and brassinosteroid and abscisic acid modulate circadian periodicity. We confirmed the pharmacology in hormone synthesis and perception mutants, as rhythmic expression is predictably altered in an array of hormone-related mutants. We genetically dissected one mechanism that integrates hormone signals into the clock, and showed that the hormone-activated ARABIDOPSIS RESPONSE REGULATOR 4 and the photoreceptor phytochrome B are elements in the input of the cytokinin signal to circadian phase. Furthermore, molecular-expression targets of this signal were found. Collectively, we found that plants have multiple input/output feedbacks, implying that many hormones can function on the circadian system to adjust the clock to external signals to properly maintain the clock system.

Original languageEnglish
JournalGenes to Cells
Issue number12
Pages (from-to)1381-92
Number of pages12
Publication statusPublished - Dec-2006
Externally publishedYes


  • Arabidopsis
  • Arabidopsis Proteins
  • Biological Clocks
  • Circadian Rhythm
  • Genes, Reporter
  • Luciferases
  • Luminescent Measurements
  • Models, Biological
  • Phytochrome B
  • Plant Growth Regulators
  • Plant Physiological Phenomena
  • Promoter Regions, Genetic
  • Seedlings
  • Journal Article
  • Research Support, Non-U.S. Gov't


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