The molecular basis of temperature compensation in the Arabidopsis circadian clock.
Circadian clocks maintain robust and accurate timing over a broad range of physiological temperatures, a characteristic termed temperature compensation. In Arabidopsis thaliana, ambient temperature affects the rhythmic accumulation of transcripts encoding the clock components TIMING OF CAB EXPRESSION1 (TOC1), GIGANTEA (GI), and the partially redundant genes CIRCADIAN CLOCK ASSOCIATED1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY). The amplitude and peak levels increase for TOC1 and GI RNA rhythms as the temperature increases (from 17 to 27 degrees C), whereas they decrease for LHY. However, as temperatures decrease (from 17 to 12 degrees C), CCA1 and LHY RNA rhythms increase in amplitude and peak expression level. At 27 degrees C, a dynamic balance between GI and LHY allows temperature compensation in wild-type plants, but circadian function is impaired in lhy and gi mutant plants. However, at 12 degrees C, CCA1 has more effect on the buffering mechanism than LHY, as the cca1 and gi mutations impair circadian rhythms more than lhy at the lower temperature. At 17 degrees C, GI is apparently dispensable for free-running circadian rhythms, although partial GI function can affect circadian period. Numerical simulations using the interlocking-loop model show that balancing LHY/CCA1 function against GI and other evening-expressed genes can largely account for temperature compensation in wild-type plants and the temperature-specific phenotypes of gi mutants.
Gould
Peter D
PD
School of Biological Sciences, University of Liverpool, Liverpool L69 7ZB, United Kingdom.
Locke
James C W
JC
Larue
Camille
C
Southern
Megan M
MM
Davis
Seth J
SJ
Hanano
Shigeru
S
Moyle
Richard
R
Milich
Raechel
R
Putterill
Joanna
J
Millar
Andrew J
AJ
Hall
Anthony
A
D000064:Acclimatization / Q000235:genetics* / Q000502:physiology; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002940:Circadian Rhythm / Q000235:genetics* / Q000502:physiology; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D025461:Feedback, Physiological; D018506:Gene Expression Regulation, Plant; D008954:Models, Biological; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D013696:Temperature; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
D029681:Arabidopsis Proteins; C114425:CCA1 protein, Arabidopsis; D004268:DNA-Binding Proteins; C121183:GI protein, Arabidopsis; C113192:LHY protein, Arabidopsis; C411822:TOC1 protein, Arabidopsis; D014157:Transcription Factors