title: Critical role for CCA1 and LHY in maintaining circadian rhythmicity in Arabidopsis.
abstract: Circadian clocks are autoregulatory, endogenous mechanisms that allow organisms, from bacteria to humans, to advantageously time a wide range of activities within 24-hr environmental cycles. CIRCADIAN CLOCK ASSOCIATED 1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY) are thought to be important components of the circadian clock in the model plant Arabidopsis. The similar circadian phenotypes of lines overexpressing either CCA1 or LHY have suggested that the functions of these two transcription factors are largely overlapping. cca1-1 plants, which lack CCA1 protein, show a short-period phenotype for the expression of several genes when assayed under constant light conditions. This suggests that LHY function is able to only partially compensate for the lack of CCA1 protein, resulting in a clock with a faster pace in cca1-1 plants. We have obtained plants lacking CCA1 and with LHY function strongly reduced, cca1-1 lhy-R, and show that these plants are unable to maintain sustained oscillations in both constant light and constant darkness. However, these plants exhibit some circadian function in light/dark cycles, showing that the Arabidopsis circadian clock is not entirely dependent on CCA1 and LHY activities.
authors: Department of Cell Biology, Institute for Childhood and Neglected Diseases, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
authors: David
authors: D
authors: Alabadí
authors: Marcelo J
authors: MJ
authors: Yanovsky
authors: Paloma
authors: P
authors: Más
authors: Stacey L
authors: SL
authors: Harmer
authors: Steve A
authors: SA
authors: Kay
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002940:Circadian Rhythm; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D003624:Darkness; D008027:Light; D009154:Mutation; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D022661:RNA, Untranslated / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D019076:Transgenes
chemical_list: D029681:Arabidopsis Proteins; C114425:CCA1 protein, Arabidopsis; D004268:DNA-Binding Proteins; C113192:LHY protein, Arabidopsis; D012333:RNA, Messenger; D018749:RNA, Plant; D022661:RNA, Untranslated; D014157:Transcription Factors