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Growth regulators Auxins Cytokinins Gibberellins Abscisic acid Ethylene Brassinosteroids All are small organics: made - PowerPoint PPT Presentation


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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 in

one part, affect

another part


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


  • 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!


  • 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


Cytokinins

Discovered as factors which induce cultured cells to divide

Haberlandt (1913): phloem chemical stimulates division


Cytokinins

Discovered as factors which induce cultured cells to divide

Haberlandt (1913): phloem chemical stimulates division

van Overbeek (1941): coconut milk stimulates division


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!


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


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


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


Cytokinins

Requires auxin to stimulate division

Kinetin/auxin determines tissue formed (original fig)


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


Cytokinins

Miller& Letham (1961) ± simultaneously found zeatin

Later found in many spp including coconut milk

Kinetintrans-Zeatin


  • 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


  • Cytokinins

    Many other natural & synthetics have been identified

    Like auxins, many are bound to sugars or nucleotides


    Cytokinins

    Many other natural & synthetics have been identified

    Like auxins, many are bound to sugars or nucleotides

    Inactive, but easily converted


    • Cytokinin Synthesis

      Most cytokinins are made at root

      apical meristem & transported to

      sinks in xylem


    • Cytokinin Synthesis

      Most cytokinins are made at root

      apical meristem & transported to

      sinks in xylem

      Therefore have inverse gradient

      with IAA


    • 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


    • 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


  • Need mutants defective in CK metabolism or signaling to detect this in vivo


  • Need mutants defective in CK metabolism or signaling to detect this in vivo

  • SAM & plants are smaller when

    [CK]


  • SAM & plants are smaller when [CK]

  • Roots are longer!


    • Cytokinin Effects

    • Usually roots have too much CK: inhibits division!

    • Cytokinins mainly act @ root & shoot meristems


    Cytokinin Effects

    Cytokinins mainly act @ root & shoot meristems

    Control G1-> S & G2-> M transition




    • Cytokinin Effects

    • Promote lateral bud growth

    • Delay leaf senescence

    • Promote cp development, even in dark


    Cytokinin Receptors

    Receptors were identified by mutation

    Resemble bacterial 2-component signaling systems



    • Cytokinin Action

      1.Cytokinin binds receptor's extracellular domain

      2. Activated protein kinases His kinase & receiver domains


    • 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)


    • 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


    • Cytokinin Action

      4. AHP-P enters nucleus &

      kinases ARR response

      regulators

      5. Type B ARR induce type A


    • Cytokinin Action

      4. AHP-P enters nucleus &

      kinases ARR response

      regulators

      5. Type B ARR induce type A

      6. Type A create cytokinin

      responses


    • 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.


    • 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


    • Gibberellins

    • Discovered by studying "foolish seedling" disease in rice

    • Hori (1898): caused by a fungus


    • Gibberellins

    • Discovered by studying "foolish seedling" disease in rice

    • Hori (1898): caused by a fungus

    • Sawada (1912): growth is caused by fungal stimulus


    • 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


    • 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


    • 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


    • Gibberellins

    • Discovered in plants in 1950s

    • "rescued" some dwarf corn & pea mutants


    • Gibberellins

    • Discovered in plants in 1950s

    • "rescued" some dwarf corn & pea mutants

    • Made rosette plants bolt


    • Gibberellins

    • Discovered in plants in 1950s

    • "rescued" some dwarf corn & pea mutants

    • Made rosette plants bolt

    • Trigger adulthood in

    • ivy & conifers


    • Gibberellins

    • "rescued" some dwarf corn & pea mutants

    • Made rosette plants bolt

    • Trigger adulthood in ivy & conifers

    • Induce growth

    • of seedless fruit


    • Gibberellins

    • "rescued" some dwarf corn & pea mutants

    • Made rosette plants bolt

    • Trigger adulthood in ivy & conifers

    • Induce growth of seedless fruit

    • Promote seed germination


    • 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


  • "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)!


  • >136 gibberellins (based on

  • structure)!

  • Most plants have >10


  • >136 gibberellins (based on

  • structure)!

  • Most plants have >10

  • Activity varies dramatically!


  • >136 gibberellins (based on

  • structure)!

  • Most plants have >10

  • Activity varies dramatically!

  • Most are precursors or

  • degradation products


  • >136 gibberellins (based on

  • structure)!

  • Most plants have >10

  • Activity varies dramatically!

  • Most are precursors or

  • degradation products

  • GAs 1, 3 & 4 are most bioactive


  • Gibberellin signaling

    Used mutants to learn about GA signaling



    • Gibberellin signaling

    • Used mutants to learn about GA signaling

    • Many are involved in GA synthesis

      • Varies during development


    • Gibberellin signaling

    • Used mutants to learn about GA signaling

    • Many are involved in GA synthesis

      • Varies during development

    • Others hit GA signaling

      • Gid = GA insensitive


    • Gibberellin signaling

    • Used mutants to learn about GA signaling

    • Many are involved in GA synthesis

      • Varies during development

    • Others hit GA signaling

      • Gid = GA insensitive

      • encode GA receptors


    • Gibberellin signaling

    • Used mutants to learn about GA signaling

    • Many are involved in GA synthesis

      • Varies during development

    • Others hit GA signaling

      • Gid = GA insensitive

      • encode GA receptors

      • Sly = E3 receptors


    • Gibberellin signaling

    • Used mutants to learn about GA signaling

    • Many are involved in GA synthesis

      • Varies during development

    • Others hit GA signaling

      • Gid = GA insensitive

      • encode GA receptors

      • Sly = E3 receptors

      • DELLA (eg rga) =

      • repressors of GA signaling


  • GAs 1, 3 & 4 are most bioactive

  • Act by triggering degradation

  • of DELLA repressors


  • 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 (GRAS)


  • Gibberellins

    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


    Gibberellins

    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


    Gibberellins & barley germination

    GA made by embryo diffuse to aleurone & trigger events leading to germination


    GA & stem elongation

    GA increase elongation, but lag >>> IAA


    GA & stem elongation

    GA increase elongation, but lag >>> IAA

    Increase cell wall creepage, but don't change pH (much)


    GA & stem elongation

    GA increase elongation, but lag >>> IAA

    Increase cell wall creepage, but don't change pH (much)

    Part of effect is increased

    expansin gene expression


    GA & stem elongation

    GA increase elongation, but lag >>> IAA

    Increase cell wall creepage, but don't change pH (much)

    Part of effect is increased

    expansin gene expression

    Another part is increased

    cell division


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