1. Regulation of Development: Vernalization
Eva Farre

2. Topics :
Overview on developmental transitions
Overview on the regulation of flowering
Regulation of flowering: vernalization

3. Which developmental transitions occur in plants?
Which factors regulate them?
Germination, flowering, bud setting, tuberization, leaf senescence, juvenile to adult transition
External factors: Temperature, nutrient availability, photoperiod, stress, water, hormones, light quality, light intensity
Internal factors: developmental stage, age

4. Vegetative Reproductive Germination Juvenile
Eucalyptus Juvenile vs Adult Leaves
Juvenile
Adult
Open questions: developmental stage, temperature
Reproductive
Adult

5. Time Transition to Flowering so that Reproduction Occurs at Appropriate Time of Year.
Spring/Summer-type annuals: vernalization has no effect.
Winter-type annuals: vernalization decreases time to flowering.
Biennials: require vernalization to flower.

6. Flowering time integrators
Light quality
Vernalization
Photoperiod
Autonomous
Gibberellin
Signaling (SD)
Flowering time integrators
Meristem identity genes
Floral Transition
Photoperiod: short day/ long day plants, examples?, what other processes are regulated by photoperiod?
Light quality influences photoperiod signaling
Vernalization: extended long cold period enhances flowering. First studies done in grasses (winter wheat
Many plants flower sooner or later due to the “activation” via the autonomous pathway.
Gibberellins enhance flowering independently of FT, buty not all plants are responsive to Gi (maybe studies haven’t been done properly)
How did they find all these genes?
Putterill et al., 2004

7. Richard Amasino
Summer and winter henbane (B) and Arabidopsis (C).
Inductive photoperiods but no vernalization.
Brassica oleracea (biennial cabbage).
Obligate vernalization requirement.
5 years without cold treatment.

8. Vernalization (status 1996):
*the promotion of flowering in response to prolonged exposure to low temperature (2-8 weeks at 4C).
*Accelerates flowering of most late flowering mutants, the one that more is fca.
*Quantitative relationship between length of cold treatment and acceleration of flowering (Napp-Zinn, 1987)
*Transmitted by mitosis but not meiosis (Evans, 1960)
*DNA metylation might be involved (Burns et all, 1993)
*FRIGIDA  FLOWERING-LOCUS C

9. Cloning of FRI Napp-Zinn (1955):
“The following aspects of the subject are reviewed: (1) conventional analysis of vernalization genes in wheat, peas and Arabidopsis; (2) population genetics and gene geography; and (3) physiological genetics”.
Arabidopsis Stockholm (late) vs Li5 (early) Li
Li + Stockholm FRI allele
Johansen et al., 2000

10. COL
Natural variation of FRI alleles
Ler
Other factors involved
Johansen et al., 2000

11. Cloning of FLC: a MADS box protein induced by FRI and repressed by cold
Cloning of FLC: problems neither Ler nor Col respond to vernalization
*Col has a non functioning FRI
*Ler has a weak FLC allele
Ler FRI-Sf2
Ler
Ler with a FRI allele from another accession is still early flowering
MUTAGENESIS
Col with a FRI allele from another accession
Michaels & Amasino (1999)

12. (Michaels & Amasino 2000)
Extra copies of FLC converts Arabidopsis to a biennial requiring vernalization to flower.

13. Who represses FLC? Light quality Vernalization Photoperiod Autonomous
Gibberellin
Signaling (SD)
Floral Transition

14. How does cold repress FLC expression?
Autonomous pathway

15. Who represses FLC? The VRN genes
FCA
vrn mutants:
vrn1 and vrn2 have no memory but “feel” cold
vrn3 no memory nor cold sensation
Chandler et al., 1996

16. vrn2 mutants have no cold memory

17. VRN's are DNA binding proteins
VRN1: a B3-domain containing DNA binding protein (H3K9 methylation)
VRN2: component of Polycomb repressor complex that mediates H3-K27 methylation
VIN3: PHD (plant homeodomain protein)

18. Who activates FLC? Light quality Vernalization Photoperiod Autonomous
PAF complex
Gibberellin
Signaling (SD)
Floral Transition
PAF+ RNA polymerase II associated fact
What is the phenotype of PAF complex mutants?
Oh et al., 2004 (van Nocker lab)
He et al., 2004
Putterill et al., 2004

19. FLC
ELF7 is the relative of yeast PAF1
He & Amasino 2005

20. FLC expression and histone modifications
HIstones

21. ELF: early flowering
VIP: vernalization insensitive
PIE: photoperiod indpendent early flowering
H3-K4 methylation: gene activation
H3-K9, H3-K27 methylation: gene inactivation

22. FLC
ELF7 is the relative of yeast PAF1
He & Amasino 2005

23. FLC promoter modifications
Methylation
Acetylation
FLC
ELF7 is the relative of yeast PAF1
He & Amasino 2005

24. Conservation of the control of flowering?
Flowering in long-day cereals

25. ARBIDOPSIS
CEREALS
Long
days
Long
days
PPD1
Vernalization
Vernalization CO CO
FRI
FT*
VRN2*
VRN1 FT
FLC
AP1
VRN1
Flowering
Flowering
Cereal genes:
VRN2: zinc-finger motif and CCT domain, similar to CO
VRN1: MADS box TF (as FLC, SOC1 etc.)
*modifications found in early flowering varieties

26. Thursday :
Circadian Clock
Photoperiodism

29. 1

30. 2

31. 2

32. 3

33. 3

34. vin3
vrn2
vrn1 4

35. BUT
Who senses the cold directly?