1. Arabidopsis flower sepal stamen carpel petal

3. 1 2 3 4 5 6 7 8 9 10 12 13 11 *

5. 1234 sepal petal stamen carpel

6. 1234 AA

7. 1234 B B

8. 1234 CC

9. B ACCA B petal stamen sepal 1122334

10. A = sepals A + B = petals C = carpels B + C = stamens Bowman and Meyerowitz, 1991 ABC Model

11. normal flower

12. B B CCCC B normalA mutant stamen carpel sepal carpel B ACCA petal stamen

13. A mutant sepals are replaced by carpels

14. B ACCA B normalB mutant ACCA sepal petal stamen carpel sepal carpel

15. B mutant petals are replaced by sepals

16. B ACCA B normalC mutant B AAAA B sepal petal stamen carpel sepal petal *

17. C mutant stamens are replaced by petals

18. C mutant carpels are replaced by a new flower

19. normal BC mutant sepal petal stamen carpel B B ACCA AAAA sepal *

20. BC double mutant all organs are sepals

21. normal ABC mutant sepal petal stamen carpel B B ACCA leaf *

22. ABC triple mutant all organs are leaves

23. “Flower organs are modified leaves.” Goethe, 1790

24. The C gene is active in cells that will form stamens and carpels petal sepal carpel leaf sepal stamen

25. What would happen if the C gene was mis-expressed in cells that would normally form sepals? petal sepal carpel leaf sepal stamen

26. ON/OFF stamens and carpels C GENE CODING REGION sepals add sepal on/off switch: remove on/off switch:

27. B normal stamen carpel sepal B ACCA petal

30. Ectopic B activity ACCA BB stamen sepal petal stamen

32. Ectopic B activity petal stamen ACCA B B

33. Ectopic B activity

34. Ectopic B and C activity stamen B B CC

35. Ectopic B and C activity

36. Ectopic A and B activity in C mutant petal * B B A A

37. Ectopic A and B activity in a C mutant

38. apetala1 mutant

39. B mutant petals are replaced by sepals

40. A mutant sepals are replaced by carpels