Growth regulators Auxins Cytokinins Gibberellins Abscisic Acid Ethylene Brassinoteroids

1. Growth regulators Auxins Cytokinins Gibberellins Abscisic Acid Ethylene Brassinoteroids Jasmonic Acid Salicylic Acid Strigolactones Nitric Oxide Sugars

2. Gibberellins • "rescued" some dwarf corn & pea mutants • Made rosette plants bolt • Trigger adulthood in ivy & conifers • Induce growth of seedless fruit • Promote seed germination • Inhibitors shorten stems: prevent lodging • >136 gibberellins (based on structure)!

3. Gibberellins GAs 1, 3 & 4 are most bioactive Made at many locations in plant Act by triggering degradation of DELLA repressors w/o GA DELLA binds & blocks activator bioactive GA binds GID1; GA-GID1 binds DELLA & marks for destruction GA early genes are transcribed, start GA responses

4. GA & other hormones GA interacts w many other hormones t/o plant life cycle

5. GA & other hormones GA interacts w many other hormones t/o plant life cycle + with auxin via DELLA & induction of GA synthesis

6. GA & other hormones • GA interacts w many other hormones t/o plant life cycle • + with auxin via DELLA & induction of GA synthesis • with cytokinins via reciprocal effects on synthesis

7. GA & other hormones GA interacts w many other hormones t/o plant life cycle + with auxin via DELLA & induction of GA synthesis - with cytokinins via reciprocal effects on synthesis - with ABA via Myb & DELLA

8. ABA Discovered as inhibitor of auxin –induced elongation (inhibitor b). Also found lots in tissues going dormant (dormin) Also found chemicals from senescing leaves & fruits that accelerated leaf abscission (abscission II) Was abscisic acid

9. ABA • Counteracts GA effects • Causes seed dormancy & • inhibits seed germination • Inhibits fruit ripening

10. ABA Also made in response to many stresses. Most is made in root & transported to shoot

11. ABA Most is made in root & transported to shoot in response to stress Closes stomates by opening Ca then closing K channels

12. ABA Synthesized during seed maturation to promote dormancy Also closes stomates in stress by opening Ca then closing K channels Induces many genes (~10% of total) via several different mechs bZIP/ABRE (ABI3, 4, 5 + AREBs)

13. ABA Synthesized during seed maturation to promote dormancy Also closes stomates in stress by opening Ca then closing K channels Induces many genes (~10% of total) via several different mechs bZIP/ABRE (ABI3, 4, 5 + AREBs) MYC/MYB

14. ABA Induces many genes (~10% of total) via several different mechs bZIP/ABRE (ABI3, 4, 5 + AREBs) MYC/MYB Jae-Hoon Lee has found 3 DWA genes that mark ABI5 (but not MYC or MYB) for destruction

15. TAIZ-Zeiger version of ABA signaling • 3 groups of receptors • GTG in PM • Resemble GPCR

16. TAIZ-Zeiger version of ABA signaling • 3 groups of receptors • GTG in PM • Resemble GPCR • IP3 has role in ABA • Unclear if GTG cause • IP3 production

17. TAIZ-Zeiger version of ABA signaling • 3 groups of receptors • GTG in PM • CHLH in Cp • Also catalyzes Chl synthesis

18. TAIZ-Zeiger version of ABA signaling • 3 groups of receptors • GTG in PM • CHLH in Cp • Also catalyzes Chl synthesis • And signals cp damage • to nucleus

19. TAIZ-Zeiger version of ABA signaling • 3 groups of receptors • GTG in PM • CHLH in Cp • PYR/PYL/RCAR • cytoplasmic

20. Schroeder version of ABA signaling • PYR/PYL/RCAR is key player • Binds ABA& inactivates PP2C

21. Schroeder version of ABA signaling • PYR/PYL/RCAR is key player • Binds ABA& inactivates PP2C • Allows SnRK2 to function

22. Schroeder version of ABA signaling • PYR/PYL/RCAR is key player • Binds ABA& inactivates PP2C • Allows SnRK2 to function • SnRK2 then kinases many targets, including ion channels, TFs & ROS producers

23. ABA signaling in Guard Cells

24. Ethylene A gas that acts as a hormone! Chinese burned incense to ripen pears 1864: leaks from street lamps damage trees Neljubow (1901): ethylene causes triple response: short stems, swelling & abnormal horizontal growth

25. Ethylene A gas that acts as a hormone! Chinese burned incense to ripen pears 1864: leaks from street lamps damage trees Neljubow (1901): ethylene causes triple response: short stems, swelling & abnormal horizontal growth Doubt (1917): stimulates abscission Gane (1934): a natural plant product

26. Ethylene Effects Climacteric fruits produce spike of ethylene at start of ripening & exogenous ethylene enhances this

27. Ethylene Effects Climacteric fruits produce spike of ethylene at start of ripening & exogenous ethylene enhances this Results: 1) increased respiration 2) production of hydrolases & other enzymes involved in ripening

28. Ethylene Effects Normally IAA from leaf tip keeps abscission zone healthy

29. Ethylene Effects Normally IAA from leaf tip keeps abscission zone healthy When IAA abscission zone becomes sensitive to ethylene

30. Ethylene Effects Normally IAA from leaf tip keeps abscission zone healthy When IAA abscission zone becomes sensitive to ethylene Ethylene induces hydrolases & leaf falls off

31. Ethylene Synthesis Made in response to stress, IAA, or during ripening

32. Ethylene Synthesis • Made in response to stress, IAA, or during ripening • Use ACC or ethephon • (which plants convert to • ethylene) to synchronize • flowering, speed • ripening

33. Ethylene Synthesis • Made in response to stress, IAA, or during ripening • Use ACC or ethephon • (which plants convert to • ethylene) to synchronize • flowering, speed • ripening • Recent work • shows ACC has • own effects

34. Ethylene Synthesis • Made in response to stress, IAA, or during ripening • Use ACC or ethephon • (which plants convert to • ethylene) to synchronize • flowering, speed • ripening • Recent work • shows ACC has • own effects • Use silver & • other inhibitors • to preserve • flowers & fruit

35. Ethylene Signaling Receptors were identified by mutants in triple response

36. Ethylene Signaling Receptors were identified by mutants in triple response Also resemble bacterial 2-component signaling systems!

37. Ethylene Signaling Receptors were identified by mutants in triple response Also resemble bacterial 2-component signaling systems! Receptor is in ER!

38. Ethylene Signaling 1. In absence of ethylene, receptors activate CTR1 which represses EIN2-dependent signaling

39. Ethylene Signaling In absence of ethylene, receptors activate CTR1 which represses EIN2-dependent signaling Upon binding ethylene, receptors inactivate CTR1 by unknown mech

40. Ethylene Signaling In absence of ethylene, receptors activate CTR1 which represses EIN2-dependent signaling Upon binding ethylene, receptors inactivate CTR1 by unknown mech 3. Active EIN2 activates EIN3

41. Ethylene Signaling In absence of ethylene, receptors activate CTR1 which represses EIN2-dependent signaling Upon binding ethylene, receptors inactivate CTR1 by unknown mech 3. Active EIN2 activates EIN3 4. EIN3 turns on genes needed for ethylene response.

42. Ethylene Signaling In absence of ethylene, receptors activate CTR1 which represses EIN2-dependent signaling Upon binding ethylene, receptors inactivate CTR1 by unknown mech 3. Active EIN2 activates EIN3 4. EIN3 turns on genes needed for ethylene response. 5. Ethylene receptor also turns off EIN3 degradation