1. Photomorphogenesis
Skotomorphogenesis (etiolation)

2. Light has an influence on seedling development
Photomorphogenesis
 inhibition of hypocotyl elongation
 opening of apical hook
 cotyledon expansion
 chloroplast development
Dark Light

3. COP and DET proteins inhibit photomorphogenesis
cop/det mutants
wild-type
Dark
Light

4. Development (realization of a phenotype from a genotype)
is controlled by
endogenous factors
intercellular regulation
 phytohormones
exogenous factors
biotic factors
abiotic factors

6. Germination of lettuce seeds (photoreversibility)
Reversible R/FR response system controlled by phytochrome

7. Phytochrome dogma
Red light Pr
Pfr
Far-red light
inactive
active

8. Phytochrome: from synthesis to action
red light
germination,
flower
Induction……
synthesis
far red light

9. blue light
red light

10. Phytochrome: homodimeric chromoprotein:
apoprotein and phytochromobilin (open chained tetrapyrrol) as chromophor form holoprotein
Arabidopsis: 5 phytochrome proteins (phyA - phy E),
differ in their apoproteins

11. R FR Strasburger, 2002 signal transduction sensor Regulatory functionPR
inactive R FR PR
inactive
PFR
active
PFR
active
Strasburger, 2002

12. Structure of phytochrome proteins
Strasburger, 2002

13. The Phytochrome apoprotein (-chromophore) is a 125kD monomer
N-terminal extension
Chromophore binding domain
Hinge region
Chromophore binding domains
PAS domain
Histidine kinase related 1
IIA
Histidine kinase related 2 IA IB
IIB
Two holoproteins (+chromophore) form a dimer

14. Pfr Pr Red light Far-red light IA IIA IB IIB IIA IA IB IIB
Two holoproteins (+chromophore) form a dimer
IIA IA IB
Chromophore binding domain
IIB
Histidine kinase related

15. Phytochrome responses vary with amount of light
VLFR: µmol x m-2
Arabidopsis seed germination
LFR: µmol x m-2
Lettuce seed germination
HIR: >1000 µmol x m-2 x s-1
Anthocyanin synthesis
Inhibition of hypocotyl elong.
Enlargement of cotyledons
Apical hook opening

16. Phytochrome responses vary with amount of light
HIR: >1000 µmol x m-2 x s-1
Inhibition of hypocotyl elongation

17. Phytochrome responses vary with amount of light
LFR: µmol x m-2
Lettuce seed germination

19. Shade avoidance reaction
Strasburger, 2002

20. Shade avoidance reaction
Strasburger, 2002

21. Shade avoidance reaction
Strasburger, 2002

22. Figure 17.9 Phytochrome is an autophosphorylating protein kinase
PP5e-Fig jpg

23. PHYA-GFP and PHYB-GFP fusion proteins migrate into the nucleus
Dark Red
PHYA-GFP
PHYB-GFP
Dark Red