Photoperiod

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Photoperiod Circadian Rhythms
Eva Farre
2
Light quality
Vernalization
Autonomous
Photoperiod
PAF complex
Gibberellin Signaling (SD)
Floral Transition
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Which processes are regulated by photoperiodism?
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How could day length be measured?
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Hour glass model
External coincidence model
Internal coincidence model
Yanovsky Kay 2003
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You need
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The circadian clock gates signaling pathways
flowering
Imaizumi and Kay, 2006
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Circadian concepts
Harmer 2008
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How to study circadian clocks?
CAB2LUCIFERASE
COTYLEDON MOVEMENT
OTHERS?
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Mechanisms of circadian clocks
Eukaryotes
Prokaryotes
Activator
KaiC
Delays
Delays
Repressor
KaiC-P
Posttranslational regulation "feedbackloops" AND
Trc/Trl feedbackloops
Transcriptional/translational feedback loops
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Mechanisms of circadian clocks
in vivo
KAIC
in vitro
KAIC
Nakajima et al., 2005 (Kondo lab)
12
The Arabidopsis circadian clock transcriptional
regulation
CCA1/LHY morning expressed transcription
factors TOC1 evening expressed pseudo-response
regulator (also called PRR1)
1. Expression level
TOC1
Delays
Delays
CCA1/LHY
Alabadi et al., 2001
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The Arabidopsis circadian clock transcriptional
regulation
CCA1/LHY morning expressed transcription
factors TOC1 evening expressed pseudo-response
regulator (also called PRR1)
2. DNA binding In vitro
A. Finding the responsible promoter element
B. Testing for binding CCA1 gel shift assay
TOC1LUC
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The Arabidopsis circadian clock transcriptional
regulation
2. DNA binding In vivo, Chromatin
Immunoprecipitation
TOC1 is associated with CCA1 promoter, probably
through a TCP TF (CHE1)
CCA1 is associated with the TOC1 promoter
Perales et al., 2007
Pruneda-Paz et al., 2009
15
The Arabidopsis circadian clock 2009 status
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The Arabidopsis circadian clock
Posttranscriptional regulation
Translation LHY Phosphorylation CCA1
CK2 PRRs unknown kinases Protein stability
PRRs Light dependent protein-protein
interactions ZTL
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A significant number of genes have cycling RNA
levels
Michael et al., 2008
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Look up for cycling of your favorite gene
in http//diurnal.cgrb.oregonstate.edu/ Todd
Mockler is coming next Monday !
19
Many processes are gated (i.e. regulated by the
clock)
for example cold
OTHERS?
Fowler et al., 2005 Thomashow lab
20
Light quality
Vernalization
Photoperiod
Autonomous
PAF complex
Gibberellin Signaling (SD)
Floral Transition
21
CONSTANS expression is regulated by the clock
toc1 mutants have a short period and flower early
Short Days
Long Days
External does not match internal rhythm
CO light high FT early flowering
Expternal matches internal rhythm
late flowering
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CONSTANS expression and natural variation
Bohlenius et al., 2006
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What happens in short day plants?
Dark/COP1
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What experiments would you do to prove that FT
protein and/or RNA is florigen ?
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FT is Florigen
Notaguchi et al., 2008 Corbesier et al., 2007
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FT is Florigen
FD bZIP transcription factor
Zeevaart, 2008
27
Light quality
Vernalization
Autonomous
Photoperiod
PAF complex
Gibberellin Signaling (SD)
Floral Transition
28
FKF Flavin-binding, kelch repeat, F-box 1
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Vierstra 2003
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1.
31
2.
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2.
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2.
Which other important protein is also expressed
exclusively in the vascular tissue?
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3.
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3.
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3.
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Sawa et al., 2005
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ZTL family of proteins are blue light receptors