1. Homework #1 is posted and due 9/17
Bonus #1 is posted and due 10/24
Discussions started this week

2. Why so many steps?

3. Multiple steps allow for signal specificity.
Different relay molecules lead to different responses

4. Multiple steps allow for signal amplification:
Calcium is a simple method of amplifying signals

5. Calcium is a common effector.
Cytoplasmic calcium levels are normally low.

6. During signal transduction, calcium can be released into the cytoplasm: Perception

7. During signal transduction, calcium can be released into the cytoplasm: Transduction

8. During signal transduction, calcium can be released into the cytoplasm: Response

9. During signal transduction, calcium can be released into the cytoplasm

10. General model of Ca++ signaling

11. General model of Ca++ signaling

12. Multiple steps allow for signal amplification:
Calcium is a simple method of amplifying signals

13. Ca++ is involved in many responses

14. Ca++ is involved in signal transduction for responses of:
in Plants
Development
Cold
Guard cell closing
Osmotic shock
Light
Fungal infection
Touch
Pollen tube growth
Wounding…
in Animals
Neurons
Muscle movement
Wounding
Development
Fertilization
Hormones …
How can there be specificity?

15. Everything has its place…

16. Some Ca++ channels have specific effectors associated with them:
Micro-domains
Ikeda, Science 12 Oct Vol 294:

17. Root nodules: Nitrogen fixation

18. Bacteria and Plants Symbiosis

19. Signaling between bacteria and plants

20. A biphasic Ca++ response to Nod factor:
1nM Nod
10nM Nod
A biphasic Ca++ response to Nod factor:
1nM Nod - toward nucleus
10nm Nod - away from nucleus
Fig 3. Shaw and Long, Plant Physiology, March 2003, Vol. 131, pp. 976–984

21. A biphasic Ca++ response to Nod factor: 1nM Nod - toward nucleus
10nm Nod - away from nucleus
Fig 3. Shaw and Long, Plant Physiology, March 2003, Vol. 131, pp. 976–984

22. Everything has its place…

23. 2 hypotheses about how Ca++ signals are transduced:
Signatures vs. Switches
Fig 1. Scrase-Field and Knight, Current Opinion in Plant Biology 2003, 6:500–506

24. Photosynthesis:
Plants can make sugar using energy from the sun, water from the ground, and CO2 from the air.

25. Stomata regulate gas exchange: CO2 in, O2 and water out
H2O
H2O

26. Stomata
open
closed

27. Opening and closing of stomata

28. Ca++ fluxes in guard cells in response to hormone or stress that cause stomatal closing.
Wildtype vs. det3 and gca2: mutants that fail to close stomata following treatment
Fig 5. Sanders et al., The Plant Cell, S401–S417, Supplement 2002

29. 2 hypotheses about how calcium signals are transduced:
Signatures vs. Switches
Fig 1. Scrase-Field and Knight, Current Opinion in Plant Biology 2003, 6:500–506

30. Signal Transduction External Stimulus Internal Effector… Effector
Response
Perception
(by receptor)
Stimulus

31. Homework #1 is posted and due 9/17
Bonus #1 is posted and due 10/24
Discussions started this week