Growth regulators All are small organics made in
- Slides: 95
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!
Auxin First studied by Darwins! Showed that a "transmissible influence" made at tips caused bending lower down No tip, no curve!
Auxin 1919: Paal showed that if tip was replaced asymmetrically, plant grew asymmetrically even in dark Uneven amounts of "transmissible influence" makes bend 1926: Went showed that a chemical that diffused from tips into blocks caused growth If placed asymmetrically get bending due to asymmetrical growth Amount of bending depends on [auxin] 1934: Indole-3 -Acetic acid (IAA) from the urine of pregnant women was shown to cause bending
Auxin IAA is the main auxin in vivo. Many synthetic auxins have been identified No obvious structural similarity, yet all work!
Auxin IAA is the main auxin in vivo. Many synthetic auxins have been identified No obvious structural similarity, yet all work! Widely used in agriculture • to promote growth (flowering, cuttings) IAA
Auxin IAA weed killers! Agent orange was 1: 1 2, 4 -D and 2, 4, 5 -T was contaminated with dioxin 2, 4 -D is still widely used: selectively kills dicots Controls weeds in monocot crops (corn, rice, wheat) Mech unclear: may cause excess ethylene or ABA production.
Auxin >90%of IAA is conjugated to sugars in vivo!
Auxin >90%of IAA is conjugated to sugars in vivo! Inactive, but readily activated!
Auxin >90%of IAA is conjugated to sugars in vivo! Inactive, but readily activated! Best way to measure [auxin] is bioassay!
Auxin >90%of IAA is conjugated to sugars in vivo! Inactive, but readily activated! Best way to measure [auxin] is bioassay! Critical concentration varies between tissues
Auxin >90%of IAA is conjugated to sugars in vivo! Inactive, but readily activated! Best way to measure [auxin] is bioassay! Critical concentration varies between tissues Roots are much more sensitive than leaves!
Auxin Critical concentration varies between tissues Roots are much more sensitive than leaves! Made in leaves & transported to roots so [IAA] decreases going down the plant Most cells are IAA sinks!
Auxin Synthesis Made in leaves & transported to roots so [IAA] decreases going down the plant Most is made from trp
Auxin Synthesis Most is made from trp Also made by trp-independent pathway: exits before trp
Auxin Synthesis Most is made from trp Also made by trp-independent pathway: exits before trp Path used varies between tissues
Auxin Synthesis Most is made from trp Also made by trp-independent pathway: exits before trp Path used varies between tissues No way to run out of IAA
Auxin Levels No way to run out of IAA! [IAA] depends on metabolism
Auxin Levels No way to run out of IAA! [IAA] depends on metabolism Most cells are IAA sinks!
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
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 Transport IAA transport therefore affects growth & development is polar and basipetal: New roots form at base of stem even if stored upside-down
Auxin Transport IAA transport therefore affects development: is polar and basipetal. New roots form at base of stem even if stored upside-down. Stem sections only move IAA basipetally
Chemiosmotic Auxin Transport 1. Apoplastic IAAH diffuses into cell • IAAH due to low p. H
Chemiosmotic Auxin Transport 1. Apoplastic IAAH diffuses into cell • IAAH due to low p. H • AUX 1 pumps in IAA- -
Chemiosmotic Auxin Transport 1. Apoplastic IAAH diffuses into cell • IAAH due to low p. H • AUX 1 pumps in IAA 2. In cell IAAH-> IAA- due to p. H 7. 2 -
Chemiosmotic Auxin Transport 1. Apoplastic IAAH diffuses into cell • IAAH due to low p. H • AUX 1 pumps in IAA 2. In cell IAAH-> IAA- due to p. H 7. 2, , draws more IAAH -
Chemiosmotic Auxin Transport 1. Apoplastic IAAH diffuses into cell • IAAH due to low p. H • AUX 1 pumps in IAA 2. In cell IAAH-> IAA- due to p. H 7. 2, draws more IAAH 3. IAA- is pumped out by PIN proteins in basal part of cell -
Chemiosmotic Auxin Transport 1. Apoplastic IAAH diffuses into cell • IAAH due to low p. H • AUX 1 pumps in IAA 2. In cell IAAH-> IAA- due to p. H 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 p. H Cycle repeats
Chemiosmotic Auxin Transport Supporting evidence 1. Some chemicals specifically block import or export
Chemiosmotic Auxin Transport Supporting evidence 1. Some chemicals specifically block import or export • Export blockers stop efflux into block, no effect on uptake
Chemiosmotic Auxin Transport Supporting evidence 1. Some chemicals specifically block import or export • Export blockers stop efflux into block, no effect on uptake • Import blockers stop uptake
Chemiosmotic Auxin Transport Supporting evidence 1. Some chemicals specifically block import or export • Export blockers stop efflux , no effect on uptake • Import blockers stop uptake • Both mess up development!
Chemiosmotic Auxin Transport Supporting evidence 1. 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!
Chemiosmotic Auxin Transport Supporting evidence 1. 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
Chemiosmotic Auxin Transport Supporting evidence 1. Some chemicals specifically block import or export • Both mess up development! 2. AUX 1 encodes an IAA-H+ symporter found at top of cell
Chemiosmotic Auxin Transport Supporting evidence 1. Some chemicals specifically block import or export • Both mess up development! 2. AUX 1 encodes an IAA-H+ symporter found at top of cell aux 1 resemble plants treated with import blockers
Chemiosmotic Auxin Transport Supporting evidence 1. Some chemicals specifically block import or export 2. AUX 1 encodes an IAA-H+ symporter found at top of cell • aux 1 resemble plants treated with import blockers 3. PINs encode IAA exporters found at cell base
Chemiosmotic Auxin Transport Supporting evidence 1. Some chemicals specifically block import or export 2. AUX 1 encodes an IAA-H+ symporter found at top of cell • aux 1 resemble plants treated with import blockers 3. PINs encode IAA exporters found at cell base • pin 1 resemble plants treated with export blockers
Auxin Action Two models: 1. Acid growth: IAA starts H+ pumping that loosens cell wall
Auxin Action Two models: 1. Acid growth: IAA starts H+ pumping that loosens cell wall • Low p. H is sufficient to cause elongation
Auxin Action Two models: 1. Acid growth: IAA starts H+ pumping that loosens cell wall • Low p. H is sufficient to cause elongation • H+ pump activators cause elongation
Auxin Action Two models: 1. Acid growth: IAA starts H+ pumping that loosens cell wall 2. Gene activation
Auxin Action IAA activates cell elongation & transcription in targets
Auxin Action IAA activates cell elongation & transcription in targets Elongation has lag of 10'
Auxin Action IAA activates cell elongation & transcription in targets Elongation has lag of 10' IAA induces PM H+ pump with 10' lag
Auxin Action IAA induces PM H+ pump with 10' lag • Acid- growth: IAA-induced p. H drop activates expansins & glucanases
Auxin Action IAA induces PM H+ pump with 10' lag • Acid- growth: IAA-induced p. H drop activates expansins & glucanases • Lag may represent time needed to move H+ pump to PM
Active transport H+ pumps lower p. H in lysosomes, stomach
Auxin Action IAA induces PM H+ pump with 10' lag • Acid- growth: IAA-induced p. H drop activates expansins & glucanases • Lag may represent time needed to move H+ pump to PM • Gnom mutants stop transport of PIN 1 to PM = links GTP exchange factor & development
Auxin Action IAA induces PM H+ pump with 10' lag • Acid- growth: IAA-induced p. H drop activates expansins & glucanases • Lag may represent time needed to move H+ pump to PM • Also have SAUR genes expressed w/in 10'!
Auxin Action Acid- growth: IAA-induced p. H drop activates expansins & glucanases Phototropism is due to more elongation on shaded side
Auxin Action Acid- growth: IAA-induced p. H drop activates extensins & glucanases Phototropism is due to more elongation on shaded side due to lateral IAA redistribution
Auxin Action Acid- growth: IAA-induced p. H drop activates extensins & glucanases Phototropism is due to more elongation on shaded side due to lateral IAA redistribution IAA export blockers stop phototropism
Auxin Action Phototropism is due to more elongation on shaded side due to lateral IAA redistribution IAA export blockers stop phototropism PIN 1 goes away in cells on light side & PIN 3 on cell sides takes over
Auxin Action Phototropism is due to more elongation on shaded side due to lateral IAA redistribution IAA export blockers stop phototropism PIN 1 goes away in cells on light side & PIN 3 on cell sides takes over IAA moves sideways
Auxin Action Phototropism is due to more elongation on shaded side due to lateral IAA redistribution IAA export blockers stop phototropism PIN 1 goes away in cells on light side & PIN 3 on cell sides takes over IAA moves sideways Lower p. H on shaded side enhances IAA uptake
Auxin Action Gravitropism Shoots bend up!
Auxin Action Gravitropism • Shoots bend up! • Roots bend down!
Auxin Action Gravitropism • Shoots bend up! • Roots bend down! Both effects are due to IAA redistribution to lower side!
Auxin Action Gravitropism • Shoots bend up, Roots bend down Both effects are due to IAA redistribution to lower side! [IAA] stimulates shoots & inhibits roots!
Apical dominance Auxin inhibits lateral bud formation • decapitate plant and lateral buds develop
Apical dominance Auxin inhibits lateral bud formation • decapitate plant and lateral buds develop • apply IAA to cut tip & lateral buds do not develop
Apical dominance Auxin induces lateral & adventitious roots
Apical dominance Auxin induces lateral & adventitious roots • Promotes cell division at initiation site
Apical dominance Auxin induces lateral & adventitious roots • Promotes cell division at initiation site • Promotes cell elongation & viability as root grows
Auxin signaling Used "auxin-resistant" mutants to find genes involved in auxin signaling
Auxin signaling Used "auxin-resistant" mutants to find genes involved in auxin signaling Many are involved in selective protein degradation!
Auxin signaling Used "auxin-resistant" mutants to find genes involved in auxin signaling Many are involved in selective protein degradation! Some auxin receptors, eg TIR 1 are E 3 ubiquitin ligases!
Auxin signaling Auxin receptors eg TIR 1 are E 3 ubiquitin ligases! Upon binding auxin they activate complexes targeting AUX/IAA proteins for degradation!
Auxin signaling Auxin receptors eg TIR 1 are E 3 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"
Auxin signaling Auxin receptors eg TIR 1 are E 3 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 ABP 1 is a different IAA receptor localized in ER • Activates PM H+ pump by sending it to PM & keeping it there
Auxin signaling ABP 1 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 ABP 1 is a different IAA receptor localized in ER • Stimulates PM H+ pump by sending it to PM & keeping it there. • Does not affect gene expression! • Some "late genes" synthesize ethylene (normally a wounding response): how 2, 4 -D kills?
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 Kinetin trans- Zeatin
Cytokinins Miller& Letham (1961) ± simultaneously found zeatin Later found in many spp including coconut milk Kinetin trans-Zeatin
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
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
Cytokinin Effects Regulate cell division • Need mutants defective in CK metabolism or signaling to detect this in vivo
Cytokinin Effects Regulate cell division • Need mutants defective in CK metabolism or signaling to detect this in vivo • SAM & plants are smaller when [CK]
• • Cytokinin Effects 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
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