1. Skotomorphogenesis Seed germination Genes and enzymes Embryo and Seed development Plant life cycle Photomorphogenesis Photoreceptors Phytochrome Cells and cell growth Phytochrome: regulation of light responses

2. SKOTOMORPHOGENESIS Photomorphogenesis Skotomorphogenesis

3. What is not regulated by light ???

4. Cotyledon expansion Reduced hypocotyl elongation Open apical hook

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

6. Light regulation mutants Short hypocotyl Expanded cotyledons Open apical hook

7. Skotomorphogenesis in the light

9. Germination of lettuce seeds (photoreversibility) Red light Far-red light inactive active

10. Phytochrome responses vary with amount of light VLFR: 0.00001 µmol x m -2 LFR: 1-1000 µmol x m -2 Arabidopsis seed germination Lettuce seed germination Anthocyanin synthesis Inhibition of hypocotyl elong. Enlargement of cotyledons Apical hook opening HIR: >1000 µmol x m -2 x s -1

11. Strasburger, 2002 Shade avoidance reaction

12. Strasburger, 2002 Shade avoidance reaction

13. Strasburger, 2002 Shade avoidance reaction

14. Strasburger, 2002 Shade avoidance reaction

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

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

17. GA signaling Nuclear import DNA binding Gene activation phytochrome signaling Nuclear import DNA binding Gene activation

18. Light regulation mutants Short hypocotyl Expanded cotyledons Open apical hook

19. Light regulation through COP1 Photoreceptors for different light qualities Downstream transcription factors CRY1 and CRY2 are negative regulators of COP1 COP1 marks transcription factors for degradation (E3 ubiquitin ligase)

20. Cop1 interaction with cryptochrome CRY1 is inactive in the darkCRY1 inhibits COP1 under blue light Electron transfer reaction

21. Cop1 complexes in plants and animals Plants: light regulated degradation of photoreceptor elements Animals: degradation of protooncogene transcription factors Negative regulation of light signaling (HY5, LAF1)Induction of tumorigenesis (p53, cJUN)

22. Light regulation through COP1 COP1CRY1 COP1CRY1 Hy5 UbUbUbUb Hy5 nucleus lightdark