1. Homework #1 is posted and due 9/20 Bonus #1 is posted and due 10/25 For Bonus points, today’s quiz is due T 9/18

2. Protein 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?

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

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

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

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

25. Ca ++ is involved in many responses

26. 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?

27. Everything has its place…

28. Ikeda, Science 12 Oct 2001 Vol 294:318-319 Some Ca ++ channels have specific effectors associated with them: Micro-domains

29. Root nodules: Nitrogen fixation

30. Bacteria and Plants Symbiosis

31. Signaling between bacteria and plants

32. Fig 3. Shaw and Long, Plant Physiology, March 2003, Vol. 131, pp. 976–984 A biphasic Ca ++ response to Nod factor: 1nM Nod - toward nucleus 10nm Nod - away from nucleus 1nM Nod10nM Nod

33. Fig 3. Shaw and Long, Plant Physiology, March 2003, Vol. 131, pp. 976–984 A biphasic Ca ++ response to Nod factor: 1nM Nod - toward nucleus 10nm Nod - away from nucleus 1nM Nod 10nM Nod 1nM Nod10nM Nod

34. Everything has its place…

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

36. Photosynthesis: Plants can make sugar using energy from the sun, water from the ground, and CO 2 from the air.

37. Stomata regulate gas exchange: CO 2 in, O 2 and water out H2OH2OH2OH2O

38. Stomata closedopen

39. Opening and closing of stomata

40. Fig 5. Sanders et al., The Plant Cell, S401–S417, Supplement 2002 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

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

42. 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?

43. Homework #1 is posted and due 9/20 Bonus #1 is posted and due 10/25 For Bonus points, today’s quiz is due T 9/18