Download presentation
Presentation is loading. Please wait.
1
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
2
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!
3
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.")
4
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
5
Auxin Action Two models: Acid growth: IAA starts H+ pumping that loosens cell wall Gene activation
6
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
7
Auxin Action Gravitropism Shoots bend up, Roots bend down Both effects are due to IAA redistribution to lower side! [IAA] stimulates shoots & inhibits roots!
8
Apical dominance Auxin inhibits lateral bud formation decapitate plant and lateral buds develop apply IAA to cut tip & lateral buds do not develop
9
Apical dominance Auxin induces lateral & adventitious roots
10
Auxin signaling Used "auxin-resistant" mutants to find genes involved in auxin signaling Many are involved in selective protein degradation!
11
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"
12
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
13
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!
14
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
15
Cytokinins Discovered as factors which induce cultured cells to divide Haberlandt (1913): phloem chemical stimulates division
16
Cytokinins Discovered as factors which induce cultured cells to divide Haberlandt (1913): phloem chemical stimulates division van Overbeek (1941): coconut milk stimulates division
17
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!
18
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
19
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
20
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
21
Cytokinins Requires auxin to stimulate division Kinetin/auxin determines tissue formed (original fig)
22
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
23
Cytokinins Miller& Letham (1961) ± simultaneously found zeatin Later found in many spp including coconut milk Kinetin trans-Zeatin
24
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
25
Cytokinins Many other natural & synthetics have been identified Like auxins, many are bound to sugars or nucleotides
26
Cytokinins Many other natural & synthetics have been identified Like auxins, many are bound to sugars or nucleotides Inactive, but easily converted
27
Cytokinin Synthesis Most cytokinins are made at root apical meristem & transported to sinks in xylem
28
Cytokinin Synthesis Most cytokinins are made at root apical meristem & transported to sinks in xylem Therefore have inverse gradient with IAA
29
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
30
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
31
Cytokinin Effects Regulate cell division Need mutants defective in CK metabolism or signaling to detect this in vivo
32
Cytokinin Effects Regulate cell division Need mutants defective in CK metabolism or signaling to detect this in vivo SAM & plants are smaller when [CK]
33
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!")
34
Cytokinin Effects Usually roots have too much CK: inhibits division! Cytokinins mainly root & shoot meristems
35
Cytokinin Effects Cytokinins mainly root & shoot meristems Control G1-> S & G2-> M transition
36
Cytokinin Effects Promote lateral bud growth
37
Cytokinin Effects Promote lateral bud growth Delay leaf senescence
38
Cytokinin Effects Promote lateral bud growth Delay leaf senescence Promote cp development, even in dark
39
Cytokinin Receptors Receptors were identified by mutation Resemble bacterial 2-component signaling systems
40
Cytokinin Action 1.Cytokinin binds receptor's extracellular domain
41
Cytokinin Action 1.Cytokinin binds receptor's extracellular domain 2. Activated protein kinases His kinase & receiver domains
42
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)
43
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
44
Cytokinin Action 4. AHP-P enters nucleus & kinases ARR response regulators 5. Type B ARR induce type A
45
Cytokinin Action 4. AHP-P enters nucleus & kinases ARR response regulators 5. Type B ARR induce type A 6. Type A create cytokinin responses
46
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.
47
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
Similar presentations
![How do plant cells grow? cell division (mitosis) cell expansion Growth rate [flux, water uptake = cell volume increase] depends on [driving force] / resistance.](/19/5757600/big_thumb.jpg "How do plant cells grow? cell division (mitosis) cell expansion Growth rate [flux, water uptake = cell volume increase] depends on [driving force] / resistance.>")
