title: TOC1 functions as a molecular switch connecting the circadian clock with plant responses to drought.
abstract: Despite our increasing knowledge on the transcriptional networks connecting abscisic acid (ABA) signalling with the circadian clock, the molecular nodes in which both pathways converge to translate the environmental information into a physiological response are not known. Here, we provide evidence of a feedback mechanism linking the circadian clock with plant responses to drought. A key clock component (TOC1, timing of CAB expression 1) binds to the promoter of the ABA-related gene (ABAR/CHLH/GUN5) and controls its circadian expression. TOC1 is in turn acutely induced by ABA and this induction advances the phase of TOC1 binding and modulates ABAR circadian expression. Moreover, the gated induction of TOC1 by ABA is abolished in ABAR RNAi plants suggesting that the reciprocal regulation between ABAR and TOC1 expression is important for sensitized ABA activity. Genetic studies with TOC1 and ABAR over-expressing and RNAi plants showed defective responses to drought, which support the notion that clock-dependent gating of ABA function is important for cellular homeostasis under dry environments.
authors.affiliation: Department of Plant Molecular Genetics, Centre for Research in Agricultural Genomics (CRAG, CSIC-IRTA-UAB), Barcelona, Spain.
authors.forename: Tommaso
authors.initials: T
authors.lastname: Legnaioli
authors.forename: Juan
authors.initials: J
authors.lastname: Cuevas
authors.forename: Paloma
authors.initials: P
authors.lastname: Mas
mesh_terms: D000040:Abscisic Acid / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D029681:Arabidopsis Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D002734:Chlorophyll / Q000235:genetics; D002940:Circadian Rhythm / Q000235:genetics; D055864:Droughts; D025461:Feedback, Physiological / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D008190:Lyases / Q000235:genetics / Q000502:physiology; D010641:Phenotype; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000502:physiology; D010937:Plant Growth Regulators / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D054046:Plant Stomata / Q000235:genetics / Q000502:physiology*; D011485:Protein Binding / Q000235:genetics; D000071636:Protein Phosphatase 2C; D015398:Signal Transduction / Q000235:genetics; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; D010937:Plant Growth Regulators; C411822:TOC1 protein, Arabidopsis; D014157:Transcription Factors; D002734:Chlorophyll; D000040:Abscisic Acid; D010749:Phosphoprotein Phosphatases; D000071636:Protein Phosphatase 2C; D008190:Lyases; C086788:magnesium chelatase