Hormone Signal transduction pathways in Plant 12/05/2008 by f5GQ325

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									 Hormone Signal transduction
     pathways in Plant

                12/05/2008

    by Men-Chi, Chang
         張孟基
   Assistant Professor
Department of Agronomy
National Taiwan university
   menchi@ntu.edu.tw
     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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