title: Multiple phytohormones influence distinct parameters of the plant circadian clock.
abstract: 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.
authors.affiliation: Max Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, D-50829 Köln, Germany.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Hanano
authors.forename: Malgorzata A
authors.initials: MA
authors.lastname: Domagalska
authors.forename: Ferenc
authors.initials: F
authors.lastname: Nagy
authors.forename: Seth J
authors.initials: SJ
authors.lastname: Davis
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001683:Biological Clocks / Q000187:drug effects* / Q000235:genetics / Q000502:physiology; D002940:Circadian Rhythm / Q000187:drug effects* / Q000235:genetics / Q000502:physiology; D017930:Genes, Reporter; D008156:Luciferases / Q000235:genetics / Q000502:physiology; D008163:Luminescent Measurements; D008954:Models, Biological; D051939:Phytochrome B / Q000235:genetics / Q000378:metabolism; D010937:Plant Growth Regulators / Q000494:pharmacology*; D018521:Plant Physiological Phenomena; D011401:Promoter Regions, Genetic; D036226:Seedlings / Q000378:metabolism
chemical_list: C113359:ARR4 protein, Arabidopsis; D029681:Arabidopsis Proteins; D010937:Plant Growth Regulators; D051939:Phytochrome B; D008156:Luciferases