Growth regulators Auxins Cytokinins Gibberellins Abscisic acid Ethylene Brassinosteroids

1. Growth regulators Auxins Cytokinins Gibberellins Abscisic acid Ethylene Brassinosteroids All are small organics: made in one part, affect another part

2. Auxin Levels No way to run out of IAA! [IAA] depends on metabolism Most cells are IAA sinks! IAA is made at shoot apex & transported down: basipetal IAA transport therefore affects growth & development

3. Chemiosmotic Auxin Transport • Apoplastic IAAH diffuses into cell • IAAH due to low pH

4. Chemiosmotic Auxin Transport • Apoplastic IAAH diffuses into cell • IAAH due to low pH • AUX1 pumps in IAA- -

5. Chemiosmotic Auxin Transport • Apoplastic IAAH diffuses into cell • IAAH due to low pH • AUX1 pumps in IAA- 2. In cell IAAH-> IAA- due to pH 7.2 -

6. Chemiosmotic Auxin Transport • Apoplastic IAAH diffuses into cell • IAAH due to low pH • AUX1 pumps in IAA- 2. In cell IAAH-> IAA- due to pH 7.2, , draws more IAAH -

7. Chemiosmotic Auxin Transport • Apoplastic IAAH diffuses into cell • IAAH due to low pH • AUX1 pumps in IAA- 2. In cell IAAH-> IAA- due to pH 7.2, draws more IAAH 3. IAA- is pumped out by PIN proteins in basal part of cell -

8. Chemiosmotic Auxin Transport • Apoplastic IAAH diffuses into cell • IAAH due to low pH • AUX1 pumps in IAA- 2. In cell IAAH-> IAA- due to pH 7.2, draws more IAAH 3. IAA- is pumped out by PIN proteins in basal part of cell 4. In apoplast IAA- -> IAAH due to low pH Cycle repeats

9. Chemiosmotic Auxin Transport Supporting evidence Some chemicals specifically block import or export

10. Chemiosmotic Auxin Transport Supporting evidence • Some chemicals specifically block import or export • Export blockers stop efflux into block, no effect on uptake

11. Chemiosmotic Auxin Transport Supporting evidence • Some chemicals specifically block import or export • Export blockers stop efflux into block, no effect on uptake • Import blockers stop uptake

12. Chemiosmotic Auxin Transport Supporting evidence • Some chemicals specifically block import or export • Export blockers stop efflux , no effect on uptake • Import blockers stop uptake • Both mess up development!

13. Chemiosmotic Auxin Transport Supporting evidence • Some chemicals specifically block import or export • Export blockers stop efflux , no effect on uptake • Import blockers stop uptake • Both mess up development! • Natural transport inhibitors have anti-cancer activity!

14. Chemiosmotic Auxin Transport Supporting evidence • Some chemicals specifically block import or export • Export blockers stop efflux , no effect on uptake • Import blockers stop uptake • Both mess up development! • Natural transport inhibitors have anti-cancer activity! • Genistein binds estrogen receptors

15. Chemiosmotic Auxin Transport Supporting evidence • Some chemicals specifically block import or export • Both mess up development! 2.AUX1 encodes an IAA-H+ symporter found at top of cell

16. Chemiosmotic Auxin Transport Supporting evidence • Some chemicals specifically block import or export • Both mess up development! 2.AUX1 encodes an IAA-H+ symporter found at top of cell aux1 resemble plants treated with import blockers

17. Chemiosmotic Auxin Transport Supporting evidence • Some chemicals specifically block import or export 2.AUX1 encodes an IAA-H+ symporter found at top of cell • aux1 resemble plants treated with import blockers 3. PINs encode IAA exporters found at cell base

18. Chemiosmotic Auxin Transport Supporting evidence • Some chemicals specifically block import or export 2.AUX1 encodes an IAA-H+ symporter found at top of cell • aux1 resemble plants treated with import blockers 3. PINs encode IAA exporters found at cell base • pin1 resemble plants treated with export blockers

19. Auxin Action • Two models: • Acid growth: IAA starts H+ pumping that loosens cell wall

20. Auxin Action • Two models: • Acid growth: IAA starts H+ pumping that loosens cell wall • Low pH is sufficient to cause elongation

21. Auxin Action • Two models: • Acid growth: IAA starts H+ pumping that loosens cell wall • Low pH is sufficient to cause elongation • H+ pump activators cause elongation

22. Auxin Action • Two models: • Acid growth: IAA starts H+ pumping that loosens cell wall • Gene activation

23. Auxin Action • IAA activates cell elongation & transcription in targets

24. Auxin Action IAA activates cell elongation & transcription in targets Elongation has lag of 10'

25. Auxin Action IAA activates cell elongation & transcription in targets Elongation has lag of 10' IAA induces PM H+ pump with 10' lag

26. Auxin Action • IAA induces PM H+ pump with 10' lag • Acid- growth: IAA-induced pH drop • activates expansins & glucanases

27. Auxin Action • IAA induces PM H+ pump with 10' lag • Acid- growth: IAA-induced pH drop activates expansins & glucanases • Lag may represent time needed to move H+ pump to PM

28. Active transport • H+ pumps • lower pH in lysosomes, stomach

29. Auxin Action • IAA induces PM H+ pump with 10' lag • Acid- growth: IAA-induced pH drop activates expansins & glucanases • Lag may represent time needed to move H+ pump to PM • Gnom mutants stop transport of PIN1 to PM = links GTP exchange factor & development

30. Auxin Action • IAA induces PM H+ pump with 10' lag • Acid- growth: IAA-induced pH drop activates expansins & glucanases • Lag may represent time needed to move H+ pump to PM • Also have SAUR genes expressed w/in 10'!

31. Auxin Action Acid- growth: IAA-induced pH drop activates expansins & glucanases Phototropism is due to more elongation on shaded side

32. Auxin Action Acid- growth: IAA-induced pH drop activates extensins & glucanases Phototropism is due to more elongation on shaded side due to lateral IAA redistribution

33. Auxin Action Acid- growth: IAA-induced pH drop activates extensins & glucanases Phototropism is due to more elongation on shaded side due to lateral IAA redistribution IAA export blockers stop phototropism

34. Auxin Action Phototropism is due to more elongation on shaded side due to lateral IAA redistribution IAA export blockers stop phototropism PIN1 goes away in cells on light side & PIN3 on cell sides takes over

35. Auxin Action Phototropism is due to more elongation on shaded side due to lateral IAA redistribution IAA export blockers stop phototropism PIN1 goes away in cells on light side & PIN3 on cell sides takes over IAA moves sideways

36. Auxin Action Phototropism is due to more elongation on shaded side due to lateral IAA redistribution IAA export blockers stop phototropism PIN1 goes away in cells on light side & PIN3 on cell sides takes over IAA moves sideways Lower pH on shaded side enhances IAA uptake

37. Auxin Action Gravitropism Shoots bend up!

38. Auxin Action • Gravitropism • Shoots bend up! • Roots bend down!

39. Auxin Action • Gravitropism • Shoots bend up! • Roots bend down! • Both effects are due to IAA redistribution to lower side!

40. Auxin Action • Gravitropism • Shoots bend up, Roots bend down • Both effects are due to IAA • redistribution to lower side! • [IAA] stimulates shoots • & inhibits roots!

41. Apical dominance • Auxin inhibits lateral bud formation • decapitate plant and lateral buds develop

42. Apical dominance • Auxin inhibits lateral bud formation • decapitate plant and lateral buds develop • apply IAA to cut tip & lateral buds do not develop

43. Apical dominance • Auxin induces lateral & adventitious roots

44. Apical dominance • Auxin induces lateral & adventitious roots • Promotes cell division at initiation site

45. Apical dominance • Auxin induces lateral & adventitious roots • Promotes cell division at initiation site • Promotes cell elongation & viability as root grows

46. Auxin signaling Used "auxin-resistant" mutants to find genes involved in auxin signaling

47. Auxin signaling Used "auxin-resistant" mutants to find genes involved in auxin signaling Many are involved in selective protein degradation!

48. Auxin signaling Used "auxin-resistant" mutants to find genes involved in auxin signaling Many are involved in selective protein degradation! Some auxin receptors, eg TIR1 are E3 ubiquitin ligases!

49. Auxin signaling Auxin receptors eg TIR1 are E3 ubiquitin ligases! Upon binding auxin they activate complexes targeting AUX/IAA proteins for degradation!

50. Auxin signaling Auxin receptors eg TIR1 are E3 ubiquitin ligases! Upon binding auxin they activate complexes targeting AUX/IAA proteins for degradation! AUX/IAA inhibit ARF transcription factors, so this turns on "early genes"