Circadian rhythm

 
 Circadian rhythm
 Background
What is the circadian clock?
The circadian clock is a time keeping mechanisms of various processes about 24 hours in living organisms in accordance with the rotation of the Earth. A typical example of the existence of circadian clock is jet lag when we travel across multiple longitudes. In plants, many of molecular and physiological responses are also regulated by endogenous circadian clock. The circadian clock is composed of inputs, core oscillators, and outputs. The inputs recognize daily changes in environment such as light and temperature, and entrain the core oscillators. The core oscillators generate and keep their rhythms around 24 hours of period even under constant conditions after the entrainment. These rhythms are translated into output activities in molecular and physiological responses. The plant circadian clock helps living organisms to prepare time-dependent processes in advance, increasing their fitness in many aspects for their entire lifespan.
A current model of the circadian clock in Arabidopsis thaliana
The circadian system forms highly regulated network structures to coordinate cyclic changes of diverse physiological processes. The Arabidopsis circadian oscillator is composed of two major interconnected feedback loops, namely the morning and evening loops. The morning loop contains CCA1/ LHY and PRR 7/9. The evening loop contains several components such as TOC1, GI, ELF 3, ELF4, and LUX, which are linked to the morning loop. The orchestrated action of the oscillator components generates an approximately 24-hour rhythm, and changes in these components can lead to alterations of rhythmic behaviors of the circadian outputs.In recent studies of our lab, we envisioned that the spatial segregation of molecules into subcellular compartments could certainly provide an important regulatory dimension in the plant circadian system. We reported that the nuclear- and cytosol-localized GI has differential functions in controlling diverse circadian processes and this spatial segregation of GI is necessary for function of the plant circadian clock network. GI defines a spatially-coded I3-FFL with LHY, in which nuclear and cytosolic GI act as positive and negative regulators of the circadian core oscillator, LHY, respectively. This spatial network ensures robustness to external noise and control performance in circadian rhythmicity.
 Contents
  – Elucidation of molecular mechanisms of GI in subnuclear compartments
– Investigation of functional relationships from inputs to outputs of circadian clock
– Investigation of spatial and temporal networking among clock core components in the plant circadian clock
Oscillator components and spatial regulatory mode in circadian clock
Diverse patterns of subnuclear localization of a clock protein with other clock components
 Member for these studies
Kim, Hyunmin
E-mail : hyunmin@postech.ac.kr
Lim, Junhyun
E-mail : doitnow1024@postech.ac.kr
Yeom, Miji
E-mail : museum@postech.ac.kr
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