1. Today: Signal Transduction the textbook has very little about signal transduction, see for more info.
Bonus #1 is due 10/02/08.
Bonus #2 is due 11/25/08.

2. Five Perceptions of Genes:
Genes act as units of heredity
Genes are seen as a cause of disease
Genes code for proteins
Genes act as switches, controlling development
Genes are replicators (selfish gene)

3. How do cells control which genes are expressed?
DNA is used to produce RNA and/or proteins, but not all genes are expressed at the same time or in the same cells.
How do cells control which genes are expressed?
Protein

4. Cells and organisms must monitor and respond to the environment.
Is there
anybody
out there?

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

8. Signal transduction step by step: Perception

9. Signal transduction step by step: Transduction

10. Signal transduction step by step: Response
– such as changes in cellular components or production of new cellular components

11. Transduction can involve activation or inactivation of proteins.

12. Cellular responses may involve changes in the expression of genes.

13. Blood sugar levels as an example of cellular responses to the environment

14. Why so many steps?

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

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

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

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

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

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

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

22. General model of Ca++ signaling

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

24. Ca++ is involved in many responses

25. 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?

26. Everything has its place…

27. Root nodules: Nitrogen fixation

28. Bacteria and Plants Symbiosis

29. Signaling between bacteria and plants

30. 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

31. 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

32. Everything has its place…
…and time.

33. 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

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

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

36. Stomata
open
closed

37. 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

38. Stomata aperture in response to Ca++ spikes:
More spikes= more closing
Fig 1. Allen et al., Nature, Vol 411: , 28 June 2001

39. Spike timing is critical for response
Fig 2. Allen et al., Nature, Vol 411: , 28 June 2001

40. Duration of spikes for stomata closing
Fig 2. Allen et al., Nature, Vol 411: , 28 June 2001

41. 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

42. Signal transduction
– such as changes in cellular components or production of new cellular components

43. How do cells express genes?

44. Today: Signal Transduction the textbook has very little about signal transduction, see for more info.
Bonus #1 is due 10/02/08.
Bonus #2 is due 11/25/08.