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Help needed for Chester Street Elementary School's STEAM Day
Science stuff with 1st – 5th graders 10-3:30 on Friday March 29 Help needed for dissecting frogs with 7th graders on Friday April 5 8:30- 10:30 in CSC223
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Growth regulators All are small organics: made in one part, affect another part Treating a plant tissue with a hormone is like putting a dime in a vending machine. It depends on the machine, not the dime!
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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
![Auxin Levels No way to run out of IAA! [IAA] depends on metabolism. Most cells are IAA sinks! IAA is made at shoot apex &](http://slideplayer.com/slide/16639667/96/images/3/Auxin+Levels+No+way+to+run+out+of+IAA%21+%5BIAA%5D+depends+on+metabolism.+Most+cells+are+IAA+sinks%21+IAA+is+made+at+shoot+apex+%26.jpg "transported down: basipetal. IAA transport therefore affects. growth & development.")
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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- -> Cycle repeats
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Auxin Action Two models: Acid growth: IAA starts H+ pumping that loosens cell wall Gene activation
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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
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Auxin Action Gravitropism Shoots bend up, Roots bend down Both effects are due to IAA redistribution to lower side! [IAA] stimulates shoots & inhibits roots!
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Apical dominance Auxin inhibits lateral bud formation decapitate plant and lateral buds develop apply IAA to cut tip & lateral buds do not develop
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Apical dominance Auxin induces lateral & adventitious roots
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Auxin signaling Used "auxin-resistant" mutants to find genes involved in auxin signaling Many are involved in selective protein degradation!
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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"
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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
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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!
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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
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Cytokinins Discovered as factors which induce cultured cells to divide Haberlandt (1913): phloem chemical stimulates division
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Cytokinins Discovered as factors which induce cultured cells to divide Haberlandt (1913): phloem chemical stimulates division van Overbeek (1941): coconut milk stimulates division
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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!
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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
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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
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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
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Cytokinins Requires auxin to stimulate division Kinetin/auxin determines tissue formed (original fig)
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Cytokinins Requires auxin to stimulate division Kinetin/auxin determines tissue formed Inspired search for natural cytokinins Miller& Letham (1961) ± simultaneously found zeatin in corn Kinetin trans- Zeatin
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Cytokinins Miller& Letham (1961) ± simultaneously found zeatin Later found in many spp including coconut milk Kinetin trans-Zeatin
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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
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Cytokinins Many other natural & synthetics have been identified Like auxins, many are bound to sugars or nucleotides
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Cytokinins Many other natural & synthetics have been identified Like auxins, many are bound to sugars or nucleotides Inactive, but easily converted
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Cytokinin Synthesis Most cytokinins are made at root apical meristem & transported to sinks in xylem
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Cytokinin Synthesis Most cytokinins are made at root apical meristem & transported to sinks in xylem Therefore have inverse gradient with IAA
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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
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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
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Cytokinin Effects Regulate cell division Need mutants defective in CK metabolism or signaling to detect this in vivo
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Cytokinin Effects Regulate cell division Need mutants defective in CK metabolism or signaling to detect this in vivo SAM & plants are smaller when [CK]
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Cytokinin Effects SAM & plants are smaller when [CK] Roots are longer!
![Cytokinin Effects SAM & plants are smaller when [CK] Roots are longer!](http://slideplayer.com/slide/16639667/96/images/33/Cytokinin+Effects+SAM+%26+plants+are+smaller+when+%5BCK%5D+Roots+are+longer%21.jpg "Cytokinin Effects SAM & plants are smaller when [CK] Roots are longer!")
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Cytokinin Effects Usually roots have too much CK: inhibits division! Cytokinins mainly root & shoot meristems
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Cytokinin Effects Cytokinins mainly root & shoot meristems Control G1-> S & G2-> M transition
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Cytokinin Effects Promote lateral bud growth
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Cytokinin Effects Promote lateral bud growth Delay leaf senescence
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Cytokinin Effects Promote lateral bud growth Delay leaf senescence Promote cp development, even in dark
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Cytokinin Receptors Receptors were identified by mutation Resemble bacterial 2-component signaling systems
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Cytokinin Action 1.Cytokinin binds receptor's extracellular domain
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Cytokinin Action 1.Cytokinin binds receptor's extracellular domain 2. Activated protein kinases His kinase & receiver domains
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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)
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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
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Cytokinin Action 4. AHP-P enters nucleus & kinases ARR response regulators 5. Type B ARR induce type A
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Cytokinin Action 4. AHP-P enters nucleus & kinases ARR response regulators 5. Type B ARR induce type A 6. Type A create cytokinin responses
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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.
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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
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