Diurnal and circadian rhythms

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Diurnal and circadian rhythms
Eva Farre
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• Objectives for today
• Students will be able to
• Distinguish between circadian vs. diurnal rhythms
• Create a diurnal model that illustrates normal
  time of physiological and metabolic processes in
  plants, then predict the changes the model in
  response to specific environmental perturbations.
• Apply the concept of entrainment by designing an
  experiment and interpreting the results.
• Explain the concepts of gating that is
  illustrated in several different models.
• Interpet the role of the circadian clock in
  photoperiodism
• Predict the evolutionary advantage of circadian
  rhythms

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Daylight saving time
Q1. What is the difference between circadian and
diurnal rhythms in animals? Talk to you
neighbor. Prepare to report out.
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(No Transcript)
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Endogenous rhythms for example circadian
Q2. What are other examples of endogenous rhythms
in living organisms? Brainstorm in your
group. Report out.
http//www.dartmouth.edu/rmcclung/NiceMovie.html
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Circadian vs. diurnal rhythms
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Daylight saving time Entrainment
How do we design experiments to test endogenous
rhythms of metabolic processes in plants?
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Entrainment experiment
Q3. Predict the growth pattern of the seedling in
frame 3. What is the rationale for your
prediction? Individuals write on carbonless
paper.
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Entrainability of circadian clocks
http//millar.bio.ed.ac.uk/video.html
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Basic structure of an eukaryotic circadian clock
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Q4 In pairs, place these physiological and
metabolic processes at the appropriate time of
day when the activity occurs. Draw and label the
model on your carbonless.
Heat adaptation genes
Anthocyanin production
Drought acclimation genes
Respiration
Photosynthesis
Respiration
Growth
Carbon assimilation
Carbon assimilation
Starch synthesis
Stomatal opening
Starch degradation
Stomatal opening
Cold acclimation genes
Convington et al. 2008 Michael et al., 2008 Nozue
et al., 2007
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Q5. What happens to circadian processes under
constant conditions?
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Q6. Interpret the patterns of CO2 assimilation
represented in this figure. Base on this
evidence, what conclusion can you draw about this
metabolic process on constant conditions?
Mutant
Wild-type
Time in continuous light
Dodd et al., 2005
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• Q7. Examine the next three figures
• Circadian clocks light
• Circadian clocks cold
• Circadian clocks flowering
• Based on the evidence provided in each figure,
  what does gates mean in each case. Remember,
  gates is a process in each of these models.
• Write in your carbonless.

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The circadian clock gates signaling pathways
light
CAB2LUC
McWatters et al., 2000
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The circadian clock gates signaling pathways
cold
Fowler et al., 2005
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The circadian clock gates signaling pathways
flowering
Imaizumi and Kay, 2006
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The right circadian clock represents a
competitive advantage
Mutant P28 30 hr Wild type 25 hr
Q8. Explain the results of this experiment in
terms of the evolutionary advantage to one of the
populations (which one? And why?)
Ouyang et al, 1998
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The circadian clock is essential for optimal
growth of plants
T24 T20 T28
Dodd et al. Science (2005)
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Concepts

• Circadian vs. diurnal rhythms
• Entrainment
• Gating
• Role of the circadian clock in photoperiodism
• Evolutionary advantage of circadian rhythms