L19 Growth Regulators II

L19 Growth Regulators II - Review of Lecture 18 Plant...

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Unformatted text preview: Review of Lecture 18 Plant Growth Regulators I:Chapter 11 1. Plant hormones 2. Signal transduction pathways 3. Auxins 4. Biochemistry and Genetics 5. Genetics of Auxin Regulation Plant Hormones 1. Auxins 2. Cytokinins 3. Gibberellins 4. Abscisic Acid 5. Ethylene 6. Brassinosteroids Plant Hormones: Auxin Darwins experiment demonstrating the role of the coleoptile tip in regulating phototropism Chap.11, pg.239 Auxin 1. Produced mainly in the shoot apical meristem, young leaves and developing fruits and seeds 2. However, all plant tissues are capable of producing low levels of IAA 3. Auxin moves both by diffusion and polar transport 4. In both shoots and roots the polar transport is basipetal (toward the base) Auxin Growth Responses From J. Callis, 2005, Nature 435 : 436 Auxin Transport 1. IAA enters the cell by passive diffusion in its protonated form (IAAH) or in its anionic form (IAA-) via an AUX1 influx carrier 2. IAA- predom inates in the cytosol (neutral pH) 3. IAA anions exit the cell only at the basal end via PIN protein efflux carriers IAAH IAA- IAAH IAA- +H + IAA- pH= 5.0 Cytosol pH=7 H + IAA- IAAH IAA- Apex Base Plant Growth Responses Signal-transduction pathways Chap.11, pg.237 Biochemistry and Genetics Understanding how hormones work What is the driving force? The driver? The engine? The wheels? Gasoline? Biochem istry and Genetics Understanding how horm ones work What is the driving force? Biochemistry: identify the parts and partially or fully reconstitute. Genetics: m odify one part at a tim e and see what happens. Genetics of Auxin Regulation Auxin response m utants Genetics of Auxin Regulation Screen for m utants affecting auxin responses 1. Screen for resistance or insensitivity to toxic levels of exogenous auxin 2. Screen for m utants that alter auxin growth responses Auxin Regulation Auxins bind to TIR1 which causes the recruitment of Aux/IAA repressors to the TIR1 complex (part of the cell protein degradation machinery) From Guilfoyle 2007, Nature 446 :621 TIR1(transport inhibitor response 1 protein) ARF (auxin response factors) Genetics of Auxin Regulation Expected Phenotypes? Lecture 19 Outline Plant Growth Regulators II: 1. Cytokinins 2. Plant tissue culture 3. Gibberellins 4. Abscisic Acid 5. Ethylene 6. Brassinosteroids 7. Other Regulators Plant Hormones: Cytokinins 1. Discovered by Johannes van Overbeek in 1941 as a growth promoting factor in coconut milk 2. This discovery lay the groundwork for in vitro methods for plant propagation (tissue culture) and launched the search for another major plant growth regulator 3. In the 1950s Skoog and co-workers partially purified this factor while Carlos Miller determined that breakdown products of DNA promoted cell division Plant Hormones: Cytokinins...
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This note was uploaded on 12/23/2010 for the course BIOL 120 taught by Professor Chuong during the Spring '09 term at Waterloo.

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L19 Growth Regulators II - Review of Lecture 18 Plant...

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