title: FBH1 affects warm temperature responses in the Arabidopsis circadian clock.
abstract: In Arabidopsis, the circadian clock allows the plant to coordinate daily external signals with internal processes, conferring enhanced fitness and growth vigor. Although external cues such as temperature can entrain the clock, an important feature of the clock is the ability to maintain a relatively constant period over a range of physiological temperatures; this ability is referred to as "temperature compensation." However, how temperature actually is perceived and integrated into the clock molecular circuitry remains largely unknown. In an effort to identify additional regulators of the circadian clock, including putative components that could modulate the clock response to changes in environmental signals, we identified in a previous large-scale screen a transcription factor that interacts with and regulates the promoter activity of a core clock gene. In this report, we characterized this transcription factor, flowering basic helix-loop-helix 1 (FBH1) that binds in vivo to the promoter of the key clock gene circadian clock-associated 1 (CCA1) and regulates its expression. We found that upon temperature changes, overexpression of FBH1 alters the pace of CCA1 expression by causing a period shortening and thus preventing the clock from buffering against this change in temperature. Furthermore, as is consistent with the current mechanistic model of feedback loops observed in the clock regulatory network, we also determined that CCA1 binds in vivo to the FBH1 promoter and regulates its expression. Together these results establish a role for FBH1 as a transcriptional modulator of warm temperature signals and clock responses in Arabidopsis.
authors.affiliation: Molecular and Computational Biology Section, University of Southern California, Los Angeles, CA 90089; and.
authors.forename: Dawn H
authors.initials: DH
authors.lastname: Nagel
authors.affiliation: Section of Cell and Developmental Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093.
authors.forename: Jose L
authors.initials: JL
authors.lastname: Pruneda-Paz
authors.affiliation: Molecular and Computational Biology Section, University of Southern California, Los Angeles, CA 90089; and stevekay@usc.edu.
authors.forename: Steve A
authors.initials: SA
authors.lastname: Kay
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics* / Q000378:metabolism; D057906:Circadian Clocks / Q000235:genetics*; D025461:Feedback, Physiological; D018506:Gene Expression Regulation, Plant; D005838:Genotype; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013696:Temperature; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D014157:Transcription Factors; C114425:CCA1 protein, Arabidopsis; C000597362:FBH1 protein, Arabidopsis