1. Photomorphogenesis
Skotomorphogenesis (etiolation)

2. Due to Pfr formation: Inhibition of hypocotyl elongation
Inhibition of cotyledons translocation
Increase of cotyledons surface area
Unfolding of the cotyledon lamina
Opening of hypocotyl hook
Development of primary leaves
Development of mature leaf primordia
Increase of negative geotropism of the hypocotyl
Development of xylem elements
Differentiation of the stomata within the epidermis of the cotyledons
Development of super-etioplasts in the cotyledons’ mesophyll
Changes in the intensity of the cell respiration
Synthesis of anthocyane in the cotyledons and the hypocotyl
Increase of carotenoid biosynthesis
Increase of chlorophyll biosynthesis
Increase of RNA biosynthesis in cotyledons
Increase of protein synthesis in cotyledons
Increase of storage fat breakdown
Increase of storage protein breakdown
Increase of ethylene biosynthesis
Acceleration of the Shibata-shift within the cotyledons
Determination of the cotyledons’ capacity to photophosphorylate
Modulation of the cotyledons’ enzyme synthesis

3. Phytochrome effects in monocots and dicots

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

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

6. Phytochrome regulation
a) localization
b) modification
c) degradation

7. Shade avoidance reaction
Strasburger, 2002

8. Shade avoidance reaction
Strasburger, 2002

9. Shade avoidance reaction
Strasburger, 2002

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

11. Gene activation through phytochrome
Nuclear import
DNA binding
Gene activation

12. Phytochrome regulation

13. Pr Pfr biological activity
Due to Pfr formation:
Pr Pfr biological activity
660nm
Pr Pfr
730nm
fast
slow
degradation products

14. Photoreceptors make plants see the light

15. Photoreceptor mutants have
an evolutionary disadvantage

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

17. Open apical
hook
Cotyledon
expansion
Reduced hypocotyl
elongation

18. closed apical
hook
Non-expanded
cotyledons
Etiolated
hypocotyl
Is skotomorphogenesis achived via active repression of photomorphogenesis

19. How to perform genetic approaches to
decifer light regulation in plants ???

20. Asking simple questions
Photomorphogenesis
in dark grown seedlings
Skotomorphogenesis
in light grown seedlings
Asking simple questions
How to perform genetic approaches to
decifer light regulation in plants ???

21. Getting complicated answers !!
Open apical hook
Expanded
cotyledons
Short
hypocotyl

22. Skotomorphogenesis in the light

23. Functions of HY gene products
HY1, HY2, HY6 phytochrome chromophore biosynthesis
HY3 phytochrome B
HY8 phytochrome A
HY4 chryptochrome1 (blue light receptor)
HY5 bZIP transcription factor

24. Functions of cop/det gene products
COP1 E3 ubiqutin ligase (phyA degradation)
DET1 Interactor COP10, COP1 DDB1 (protein degradation)
COP9 signalosome, proteasome complex
DET2/DWF2 brassinosteroid biosynthesis

26. Measuring irradiation:
chloroplast movements (Lemna) depending
on light intensity
Dark Low light High light

27. Measuring time Measuring time Measuring time Measuring time

28. Processes regulated by photoperiod
flower induction
begin and end of dormancy
cambium activity
growth rate
formation of storage organs
development of freezing resistance
senescence

29. SD: 15 weeks 10hrs light
SD: 14 weeks 10hrs light
1 week 24 hrs light
SD: 12 weeks 10hrs light
3 weeks 24 hrs light

30. Short day plant
Chrysanthemum
Long day plant
Spinach
short day long day

31. R (660 nm) is effective; effect is eliminated by FR (730 nm) pulse
Short day plant (long night)
Long day plant (short night)
R (660 nm) is effective; effect is eliminated by FR (730 nm) pulse

32. Flower induction depends on length of dark period per day
Long day plants: days length longer than dark period
Short day plants: day length shorter than dark period