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Photoperiod & Circadian Rhythms

Photoperiod & Circadian Rhythms. Eva Farre. Light quality. Vernalization. Autonomous. Photoperiod. PAF complex. Gibberellin Signaling (SD). Floral Transition. Which processes are regulated by photoperiodism?. How could day length be measured?. Hour glass model.

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Photoperiod & Circadian Rhythms

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  1. Photoperiod & Circadian Rhythms Eva Farre

  2. Light quality Vernalization Autonomous Photoperiod PAF complex Gibberellin Signaling (SD) Floral Transition

  3. Which processes are regulated by photoperiodism?

  4. How could day length be measured?

  5. Hour glass model External coincidence model Internal coincidence model Yanovsky & Kay 2003

  6. You need:

  7. The circadian clock “gates” signaling pathways: flowering Imaizumi and Kay, 2006

  8. Circadian concepts Harmer 2008

  9. How to study circadian clocks? CAB2:LUCIFERASE COTYLEDON MOVEMENT OTHERS?

  10. Mechanisms of circadian clocks Eukaryotes Prokaryotes Activator KaiC Delays Delays Repressor KaiC-P Posttranslational regulation "feedbackloops" AND Trc/Trl feedbackloops Transcriptional/translational feedback loops

  11. Mechanisms of circadian clocks in vivo KAIC KAIC in vitro 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

  13. 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 TOC1:LUC

  14. 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

  16. The Arabidopsis circadian clock: Posttranscriptional regulation Translation: LHY Phosphorylation: CCA1: CK2 PRRs: unknown kinases Protein stability: PRRs Light dependent protein-protein interactions: ZTL

  17. A significant number of genes have cycling RNA levels Michael et al., 2008

  18. 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 Autonomous Photoperiod 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

  22. CONSTANS expression and natural variation Bohlenius et al., 2006

  23. What happens in short day plants? Dark/COP1

  24. What experiments would you do to prove that FT protein and/or RNA is florigen ?

  25. FT is Florigen Notaguchi et al., 2008 Corbesier et al., 2007

  26. 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

  29. Vierstra 2003

  30. 1.

  31. 2.

  32. 2.

  33. 2. Which other important protein is also expressed exclusively in the vascular tissue?

  34. 3.

  35. 3.

  36. 3.

  37. Sawa et al., 2005

  38. ZTL family of proteins are blue light receptors

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