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Growth regulators Auxins Cytokinins Gibberellins Abscisic acid Ethylene Brassinosteroids All are small organics: made i

Growth regulators Auxins Cytokinins Gibberellins Abscisic acid Ethylene Brassinosteroids All are small organics: made in one part, affect another part. Auxin signaling Auxin receptors eg TIR1 are E3 ubiquitin ligases !

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Growth regulators Auxins Cytokinins Gibberellins Abscisic acid Ethylene Brassinosteroids All are small organics: made i

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

  2. 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" Some early genes turn on 'late genes" needed for development

  3. Auxin signaling • ABP1 is a different IAA receptor localized in ER • Activates PM H+ pump by sending it to PM & keeping it there • Does not affect gene expression!

  4. Auxin & other growth regulators • Some "late genes" synthesize ethylene (normally a wounding response): how 2,4-D kills? • Auxin/cytokinin determines • whether callus forms roots or shoots

  5. Cytokinins Discovered as factors which induce cultured cells to divide Haberlandt (1913): phloem chemical stimulates division

  6. Cytokinins Discovered as factors which induce cultured cells to divide Haberlandt (1913): phloem chemical stimulates division van Overbeek (1941): coconut milk stimulates division

  7. Cytokinins Discovered as factors which induce cultured cells to divide Haberlandt (1913): phloem chemical stimulates division van Overbeek (1941): coconut milk stimulates division Miller… Skoog (1955): degraded DNA stimulates division!

  8. Cytokinins Discovered as factors which induce cultured cells to divide Haberlandt (1913): phloem chemical stimulates division van Overbeek (1941): coconut milk stimulates division Miller… Skoog (1955): degraded DNA stimulates division! Kinetin was the breakdown product

  9. Cytokinins Discovered as factors which induce cultured cells to divide Haberlandt (1913): phloem chemical stimulates division van Overbeek (1941): coconut milk stimulates division Miller… Skoog (1955): degraded DNA stimulates division! Kinetin was the breakdown product Derived from adenine

  10. Cytokinins Discovered as factors which induce cultured cells to divide Haberlandt (1913): phloem chemical stimulates division van Overbeek (1941): coconut milk stimulates division Miller… Skoog (1955): degraded DNA stimulates division! Kinetin was the breakdown product Derived from adenine Requires auxin to stimulate division

  11. Cytokinins Requires auxin to stimulate division Kinetin/auxin determines tissue formed (original fig)

  12. Cytokinins Requires auxin to stimulate division Kinetin/auxin determines tissue formed Inspired search for natural cytokinins Miller& Letham (1961) ± simultaneously found zeatin in corn Kinetintrans- Zeatin

  13. Cytokinins Miller& Letham (1961) ± simultaneously found zeatin Later found in many spp including coconut milk Kinetintrans-Zeatin

  14. Cytokinins • Miller& Letham (1961) ± • simultaneously found zeatin • Later found in many spp • including coconut milk • Trans form is more active, • but both exist (& work) • Many other natural & • synthetics have been identified

  15. Cytokinins Many other natural & synthetics have been identified Like auxins, many are bound to sugars or nucleotides

  16. Cytokinins Many other natural & synthetics have been identified Like auxins, many are bound to sugars or nucleotides Inactive, but easily converted

  17. Cytokinin Synthesis Most cytokinins are made at root apical meristem & transported to sinks in xylem

  18. Cytokinin Synthesis Most cytokinins are made at root apical meristem & transported to sinks in xylem Therefore have inverse gradient with IAA

  19. Cytokinin Synthesis Most cytokinins are made at root apical meristem & transported to sinks in xylem Therefore have inverse gradient with IAA Why IAA/CK affects development

  20. Cytokinin Synthesis Most cytokinins are made at root apical meristem & transported to sinks in xylem Therefore have inverse gradient with IAA Why IAA/CK affects development Rapidly metabolized by sink

  21. Cytokinin Effects Regulate cell division • Need mutants defective in CK metabolism or signaling to detect this in vivo

  22. Cytokinin Effects Regulate cell division • Need mutants defective in CK metabolism or signaling to detect this in vivo • SAM & plants are smaller when [CK]

  23. Cytokinin Effects • SAM & plants are smaller when [CK] • Roots are longer!

  24. Cytokinin Effects • Usually roots have too much CK: inhibits division! • Cytokinins mainly act @ root & shoot meristems

  25. Cytokinin Effects Cytokinins mainly act @ root & shoot meristems Control G1-> S & G2-> M transition

  26. Cytokinin Effects • Promote lateral bud growth

  27. Cytokinin Effects • Promote lateral bud growth • Delay leaf senescence

  28. Cytokinin Effects • Promote lateral bud growth • Delay leaf senescence • Promote cp development, even in dark

  29. Cytokinin Receptors Receptors were identified by mutation Resemble bacterial 2-component signaling systems

  30. Cytokinin Action 1.Cytokinin binds receptor's extracellular domain

  31. Cytokinin Action 1.Cytokinin binds receptor's extracellular domain 2. Activated protein kinases His kinase & receiver domains

  32. Cytokinin Action 1.Cytokinin binds receptor's extracellular domain 2. Activated protein kinases His kinase & receiver domains 3. Receiver kinases His-P transfer relay protein (AHP)

  33. Cytokinin Action 1.Cytokinin binds receptor's extracellular domain 2. Activated protein kinases His kinase & receiver domains 3. Receiver kinases His-P transfer relay protein (AHP) 4. AHP-P enters nucleus & kinases ARR response regulators

  34. Cytokinin Action 4. AHP-P enters nucleus & kinases ARR response regulators 5. Type B ARR induce type A

  35. Cytokinin Action 4. AHP-P enters nucleus & kinases ARR response regulators 5. Type B ARR induce type A 6. Type A create cytokinin responses

  36. Cytokinin Action 4. AHP-P enters nucleus & kinases ARR response regulators 5. Type B ARR induce type A 6. Type A create cytokinin responses 7. Most other effectors are unknown but D cyclins is one effect.

  37. Auxin & other growth regulators • Some "late genes" synthesize ethylene (normally a wounding response): how 2,4-D kills? • Auxin/cytokinin determines whether callus forms roots or shoots • Auxin induces Gibberellins

  38. Gibberellins • Discovered by studying "foolish seedling" disease in rice • Hori (1898): caused by a fungus

  39. Gibberellins • Discovered by studying "foolish seedling" disease in rice • Hori (1898): caused by a fungus • Sawada (1912): growth is caused by fungal stimulus

  40. Gibberellins • Discovered by studying "foolish seedling" disease in rice • Hori (1898): caused by a fungus • Sawada (1912): growth is caused by fungal stimulus • Kurosawa (1926): fungal filtrate causes these effects

  41. Gibberellins • Discovered by studying "foolish seedling" disease in rice • Kurosawa (1926): fungal filtrate causes these effects • Yabuta (1935): purified gibberellins from filtrates of • Gibberellafujikuroi cultures

  42. Gibberellins • Discovered by studying "foolish seedling" disease in rice • Kurosawa (1926): fungal filtrate causes these effects • Yabuta (1935): purified gibberellins from filtrates of • Gibberellafujikuroi cultures • Discovered in • plants in 1950s

  43. Gibberellins • Discovered in plants in 1950s • "rescued" some dwarf corn & pea mutants

  44. Gibberellins • Discovered in plants in 1950s • "rescued" some dwarf corn & pea mutants • Made rosette plants bolt

  45. Gibberellins • Discovered in plants in 1950s • "rescued" some dwarf corn & pea mutants • Made rosette plants bolt • Trigger adulthood in • ivy & conifers

  46. Gibberellins • "rescued" some dwarf corn & pea mutants • Made rosette plants bolt • Trigger adulthood in ivy & conifers • Induce growth • of seedless fruit

  47. Gibberellins • "rescued" some dwarf corn & pea mutants • Made rosette plants bolt • Trigger adulthood in ivy & conifers • Induce growth of seedless fruit • Promote seed germination

  48. 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

  49. 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)!

  50. Gibberellins • >136 gibberellins (based on • structure)! • Most plants have >10

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