Hormone Signal transduction pathways in Plant 12/05/2008 by Men-Chi, Chang 張孟基 Assistant Professor Department of Agronomy National Taiwan university firstname.lastname@example.org Related review papers published 1. A. Bishopp, A.P. Mähönen, Y. Helariutta(2006) Signs of change: hormone receptors that regulate plant development. Development 133, 1857-1869 (suggested reading)* 2. A.K. Spartz and W.M. Gray. (2008) Plant hormone receptors: new perceptions. Genes & Dev. 22: 2139-2148 (suggested reading)* 3. P. McCourt and R. Creelman. (2008) The ABA receptors – we report you decide. Current Opinion in Plant Biology, 11:474–478 4. A. Wasilewsk, F. Vla, C. Sirichandr, Y. Redkob, F. Jammesc, C. Valona, N. F. Freya and J. Leunga. (2008) An update on abscisic acid signaling in plants and more . . . Molecular Plant Vol 1, 2:198–217. 5. M. D Kendrick and C. Chang. (2008) Ethylene signaling: new levels of complexity and regulation. Current Opinion in Plant Biology 11:479– 485 6. Lynn M. Hartweck (2008) Gibberellin signaling. Planta 229:1–13 7. S Lau, G. Ju¨rgens, and I. D. Smet. (2008) The evolving complexity of the auxin pathway. The Plant Cell 20: 1738–1746. 8. I. Galis, E. Gaquerel, S. P. Pandey, I. T. Baldwin. (2008) Molecular mechanisms underlying plant memory in JA-mediated defence responses. Plant, Cell and Environment 1-11. 9. B Muller and J Sheen. (2007) Advance in cytokinin signaling. Science 318: 68-69. 10. J. M. Gendron and Z.Y. Wang (2007) Multiple mechanisms modulate brassinosteroid signaling. Current Opinion in Plant Biology 10:436– 441. Talk Outline I. General introduction about plant hormones (phytohormones) a. types. b. physiological functions. c. differences compared with animal’s hormones. d. ways or approaches of studies. II. Molecular mechanism of various plant hormone signal transduction pathways (a) ubiquitin-dependent protein degradation. (negative regulator) (b) tow-component system (phospho-relay). III. How different hormones are recognized by their corresponding hormone receptors? a. auxin-TIR1-IAA/AUX b. GA-GID1-DELLA IV. Plant hormones vs. Plant growth regulators: manipulation of plant growth and development with knowledge from plant hormone signal transduction pathways. ex. second green revolution I. General introduction about plant hormones (phytohormones) Analogy view of cell signaling transduction pathway CPU Input (Central Output (command) Processing (performance) Keyboard Printer Signal Unit) Chip Signal perception Response Endogenous: Signal Morphogenesis phytohormone Transduction change, Exogenous: Network Growth development environmental Compiling, differentiation cue Integration, processing A wide range of disparate external and internal signals is monitored by plants and used to compute appropriate developmental responses Molecular Cell Biology 2: 307- 314 (2001) Various signaling transduction pathways in plants Calcium (Ca+2) signaling (regulatory network) Lipid signaling transduction pathway Reactive oxygen species (ROS) signaling Nitric oxide (NO) signaling transduction pathway Sugar sensing responsive pathway Wounding-signal transduction pathway (plant-pathogen interaction) Light signaling responsive pathway Biological o’clock (circadian rhythm) regulatory pathway Development regulatory pathway e. g. flowering (autonomous), lead, root, trichome formation root apical meristem (RAM) shoot apical meristem (SAM) formation polarity and cell cytoskeleton rearrangement Specific cell fate determination and differentiation (Xylem and phloem specification, root organization (patterning)) Abiotic stress signaling pathways (salt, drought, heat, cold, metal, vernalization etc.) Plant hormone signaling transduction (auxin, ethylene, cytokinin, gibberellin, abscisic acid, brasinosteroid, jasmonic acid etc.) Definition of plant hormone (phytohormone) 1. The word hormone is derived from the Greek verb meaning to excite. 2. hormones are organic substances synthesized in one tissue and transported out where their presence results in physiological responses ( not always true; may act at or close to synthesis site). They are required in minute amounts (10-6 to 10 -8M). 3. Each hormone may result in multiple effects -- the particular effect depending on a number of factors: (a) the presence of other hormones and the presence of activator molecules ( calcium, sugars) (b) the amount of the hormone (dosage or concentration) (c) the sensitivity of that tissue to the hormone. (d) the condition of the plant itself is critical: what is the condition of the plant? its age? Site of action x developmental stage x concentration of hormone? Crosstalk and specificity? Chemical Structures of the Plant Hormones Salicylic acid plant hormones synthesis sites and their major functions Effects of plant hormones on plant growth and development Embryogenesis Senescence (Cell division, expansion, differentiation and cell death) What are the differences between plant hormones and animal hormones? Main approaches used to study plant hormone perception, signal transduction biosynthesis and responses 1. Molecular genetics approach hormone biosynthetic mutants vs. hormone insensitive mutants 2. Biochemistry approach hormone binding protein (photo-affinity probe, affinity chromatography, immunopurification) 3. Inhibitors approach kinase/phosphatase, G-protein, PKC etc. inhibitors Dissect plant hormone signal transduction pathways by molecular genetic analysis Triple response Chronological events and persons involved in identification of different hormone receptors 2007 (CHLH, GCR2) Summary of molecular components involved in plant hormone signaling transduction 1. Auxin: TIR1: F-box protein (Ubiquitin conjugated ligase) PIN1 (pin-formed 1) Aux/IAA repressor 2. Ethylene: histidine kinase Raf-like kinase CTR1 Mitogen activated protein kinase cascade 3. Cytokinin: phosphorelay (two-component system) 4. Gibberellin: G protein and DELLA protein hexosamine (NAcGlu) 5. Abscisic acid: PP2C protein, SnRK protein kinase Farnesylation 6. Brasinosteroid: BRI1 (LRR-RLK) II. Molecular mechanism of various plant hormone signal transduction pathways (a) ubiquitin-dependent protein degradation. (negative regulator) An overview of the ubiquitination process in plants E1; UBA, ubiquitin activating enzyme E2: UBC, ubiquitin conjugatingenzyme E3: ubiquitin protein ligase RBX: ring-box protein CUL: cullin CRL:cullin ring ligase HECT: homologous to E6-AP COOH terminus RING: really interesting new gene protein domain SCF: SKP1-Cullin-F-box SKP: S phase kinase associated protein F-box: SKP/ASK interaction motif in cyclin F Annals of Botany 99: 787-822 (2007) Biological significance of ubiquitin/proteosome system (UPS) in plants 1. UPS was involved in different processes of plant life, including organ initiation and embryogenesis patterning, light signaling , circadian clock regulation ,hormone production, perception and signal transduction, and in plant defense. 2. The covalent attachment of ubiquitin to a substrate protein changes its fate. Notably, proteins typically tagged with a lysine48-linked polyubiquitin chain become substrates for degradation by the 26S proteasome. 3. Over 6 % (1,500 genes) of the predicted Arabidopsis genome encodes proteins involved in the UPS, and analyses of other plant genomes demonstrate a similar abundance of UPS-related genes. E1 (1); E2 (1); UEV (8); E3 (mast abundant): HECT (7); Ring (450); U-domain (61); cullin (11); F-box (700) BTB (80) Phenotypes associated with the auxin and gibberellin receptor mutants Development 133, 1857-1869 (2006) Ubiquitin-ligase based receptors ( auxin, jasmonates and gibberellin) GENES & DEVELOPMENT 22:2139–2148 (2008) Phenotypes associated with the brassinosteroid, ethylene, cytokinin and abscisic acid receptor mutants Development 133, 1857-1869 (2006) Brassinosteroid signaling pathway Development 133, 1857-1869 (2006) Receptor-co-receptor activation and initiation of brassinosteroid signaling cascade Current Biology (2008) 18 (20): R963-R965 II. Molecular mechanism of various plant hormone signal transduction pathways (b) tow-component system (phospho-relay). Two-component or phospho-relay circuitry Composition of the transmembrane phytohormone receptors Development 133, 1857-1869 (2006) Ethylene and cytokinin signaling pathways (two component system) Development 133, 1857-1869 (2006) Science 318: 68-69.(2007) Abscisic acid receptors: multiple signal-perception sites 1. FCA is a nuclear receptor for ABA controling flowering. 2. ABAR/CHLH is a plastid receptor for ABA controlling major ABA response. 3. GCR2 is a plasma membrane receptor for ABA controlling ABA physiological response. “ABA-binding pocket” Annals of Botany 101: 311–317, 2008 III. How different hormones are recognized by their corresponding hormone receptors? a. auxin-TIR1-IAA/AUX b. GA-GID1-DELLA Nature 446: 640 – 645 (2007) Crystal structure of the TIR1–ASK1 complex with auxin and theIAA7 degron peptide Nature 446, 2007 auxin function as a „molecular glue‟ to enhanceTIR1–substrate interactions Nature 456:459 – 464 (2008) Structure of the GA3–GID1A–DELLA complex IV. Plant hormones vs. Plant growth regulators: manipulation of plant growth and development with knowledge from plant hormone signal transduction pathways. Genetic manipulation of GA metabolism or signal transduction pathway? (second Green Revolution?) Thanks for your attention! Thanks for your attention!
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