Diurnal and circadian rhythms

Eva Farre

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

Daylight saving time

Q1. What is the difference between circadian and diurnal rhythms in animals?

Talk to you neighbor. Prepare to report out.

Endogenous rhythms: for example circadian

http://www.dartmouth.edu/~rmcclung/NiceMovie.html

Q2. What are other examples of endogenous rhythms in living organisms?

Brainstorm in your group.Report out.

Circadian vs. diurnal rhythms

Daylight saving time: Entrainment

How do we design experiments to test endogenous rhythms of metabolic processes in plants?

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.

Entrainability of circadian clocks

Thain et al., Curr Biol 2000

CAB2:LUC

http://millar.bio.ed.ac.uk/video.html

Basic structure of an eukaryotic circadian clock

Photosynthesis

Convington et al. 2008Michael et al., 2008Nozue et al., 2007

Heat adaptation genes

Drought acclimation genes

Stomatal opening

Cold acclimation genes

Anthocyanin production

Starch degradation

Growth

Carbon assimilation

Starch synthesis

Respiration

Carbon assimilation

Stomatal opening

Respiration

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.

Q5. What happens to circadian processes under constant conditions?

Time in continuous light

Dodd et al., 2005

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? MutantWild-type

Q7. Examine the next three figures:

1. Circadian clocks: light

2. Circadian clocks: cold

3. 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.

CAB2:LUCMcWatters et al., 2000

The circadian clock “gates” signaling pathways: light

Fowler et al., 2005

The circadian clock “gates” signaling pathways: cold

The circadian clock “gates” signaling pathways: flowering

Imaizumi and Kay, 2006

Ouyang et al, 1998

The right circadian clock represents a competitive advantage

Mutant P28= 30 hrWild type = 25 hr

Q8. Explain the results of this experiment in terms of theevolutionary advantage to one of the populations (which one? And why?)

Dodd et al. Science (2005)

The circadian clock is essential for optimal growth of plants

T24T20T28

Period 28 h 20 h

Concepts:

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